Image reproduction apparatus performing interfield or interframe interpolation

An image reproduction apparatus which converts a sampling frequency from a first frequency to a second frequency, performs interfield interpolation at a third frequency, and converts the sampling frequency from the third frequency to the first frequency, wherein the interfield-interpolation is performed at the first frequency between signals one field apart from each other. The apparatus also converts a number of vertical scanning lines to convert a high definition TV signal of the MUSE format to a signal of NTSC format, sets a scanning period used in the vertical scanning line conversion, and generates a coefficient used in the vertical scanning line conversion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates, for example, to an image reproduction 
apparatus which is a high definition TV receiver for reproducing a high 
definition TV signal transmitted in MUSE format. 
2. Description of Related Art 
FIG. 1 is a block diagram showing a configuration of a conventional high 
definition TV receiver (see "MUSE High Definition TV Transmission System", 
compiled by the Institute of Electronics, Information and Communication 
Engineers). In FIG. 1, reference numeral 1 designates an input processing 
section to de-emphasize a MUSE signal or detect a control signal. The 
input processing section 1 outputs the processed MUSE signal to a frame 
memory 2, an interframe interpolation circuit 3, a two-dimensional 
interpolation circuit 8 and a motion detection circuit 11. The frame 
memory 2 delays by one frame the video period of the MUSE signal processed 
by the input processing section 1, and outputs a delayed MUSE signal to 
the interframe interpolation circuit 3 and the motion detection circuit 
11. The interframe interpolation circuit 3 interpolates the signals at the 
two ends of the frame memory 2 and outputs the signal thus processed to an 
LPF circuit 4. The LPF circuit 4 subjects the output of the interframe 
interpolation circuit 3 to 12-MHz low-pass filtering, and outputs the 
signal thus filtered to a sampling frequency conversion circuit 5. The 
frequency changer circuit 5 converts the output signal of 32.4-MHz in 
sampling frequency from the LPF circuit 4 into a 24.3-MHz sampling 
frequency, and outputs the signal thus converted to a field memory 6 and a 
48.6-MHz interfield interpolation circuit 7. The field memory 6 delays the 
output of the sampling frequency conversion circuit 5 by one field and 
outputs the delayed signal to the 48.6-MHz interfield interpolation 
circuit 7. The 48.6-MHz interfield interpolation circuit 7 interpolates 
the signals at the two ends of the field memory 6 and outputs the 
resulting signal a mixer circuit 12. 
The two-dimensional interpolation circuit 8 two-dimensionally interpolates 
the signal processed at the input processing section 1 in field dimension, 
and outputs the processed signal to a sampling frequency conversion 
circuit 9. The sampling frequency conversion circuit 9 converts the output 
signal of the two-dimensional interpolation circuit 8 having a sampling 
frequency of 32.4-MHz to a sampling frequency of 48.6-MHz, and outputs the 
signal thus converted to the mixer circuit 12. Also, numeral 10 designates 
a motion detection memory for delaying the video period of the MUSE signal 
by at least one frame. The motion detection circuit 11 detects a motion 
area from the outputs of the input processing section 1, the frame memory 
2 and the memory 10, and outputs the resulting detection signal to the 
mixer circuit 12. The mixer circuit 12 mixes the output of the 48.6-MHz 
interfield interpolation circuit 7 with that of the sampling frequency 
conversion circuit 9 on the basis of the detection signal from the motion 
detection circuit 11. 
Now, the operation will be explained. The MUSE signal inputted to the input 
processing section 1 is subjected to such input processings as de-emphasis 
and control signal detection. The MUSE signal thus subjected to these 
input processings undergoes separate processings for still and moving 
images and the resulting signals are mixed at the mixer circuit 12. 
First, the still image processing is done in such a manner that the output 
of the input processing section 1 is delayed by one frame at the frame 
memory 2, and the signals at the ends of the frame memory 2 are temporally 
interpolated at the interframe interpolation circuit 3. The signal thus 
subjected to interframe interpolation has a sampling frequency of 
32.4-MHz, but has an aliasing component of at least 12-MHz. In order to 
remove this aliasing component, the same signal is subjected to low-pass 
filtering of 12-MHz at the LPF circuit 4. The output of the LPF circuit 4 
is converted to 24.3-MHz in sampling frequency at the sampling frequency 
conversion circuit 6. For conversion from 32.4 MHz to 24.3-MHz, the 
32.4-MHz signal is zeroth-order interpolated to 97.2-MHz, and then 
subsampled at 24.3-MHz. The signal thus frequency-converted to 24.3-MHz is 
delayed at the field memory 6 by one field. The input and output signals 
of the field memory 6 are interpolated by the 48.6-MHz interfield 
interpolation circuit 7. The interfield interpolation requires 
two-dimensional filtering in view of the reproduction range of the MUSE 
signal. 
In the moving image processing, on the other hand, the signal subjected to 
input processings at the input processing section 1 is two-dimensionally 
interpolated at the two-dimensional interpolation circuit 8. The output of 
the two-dimensional interpolation circuit 8 has a sampling frequency of 
32.4-MHz. In order to match this frequency with the final sampling 
frequency for the still image processing, the output signal of the circuit 
8 is converted to 48.6-MHz at the sampling frequency conversion circuit 9. 
For conversion from 32.4-MHz to 48.6-MHz, in the same way as the 
processing at the sampling frequency conversion circuit 5, the 32.4-MHz 
signal is zeroth-order interpolated to 97.2-MHz and subsampled at 
48.6-MHz. 
The motion detection circuit 11 for mixing the still and moving image 
processings detects a motion area from the outputs of the input processing 
section 1, the frame memory 2 and the memory 10 capable of delaying at 
least one frame. Normally, a motion area is detected by using a 
one-interframe difference signal subjected to 4-MHz low-pass filtering, a 
two-interframe difference signal and the same two-interframe difference 
signal delayed by one frame. Also, a motion vector signal is detected from 
the control signal multiplexed on the MUSE signal at the input processing 
section 1, and a dedicated memory is used for horizontal and vertical 
motion vectors at the motion detection circuit 11, the interframe 
interpolation circuit 3 and the 48.6-MHz interfield interpolation circuit 
7. 
On the basis of the motion area information detected by the motion 
detection circuit 11, the output of the 48.6-MHz interfield interpolation 
circuit 7 that has undergone the still image processing and the output of 
the sampling frequency conversion circuit 9 that has undergone the moving 
image processing are mixed with each other at the mixer circuit 12. 
Since the conventional high definition TV receiver (image reproduction 
apparatus) is configured as described above, the 48.6-MHz interfield 
interpolation is effected for still image processing. This requires a 
12-MHz LPF circuit, a sampling frequency conversion circuit and a 48.6-MHz 
interfield interpolation circuit, resulting in a bulky circuit. Also, a 
dedicated frame memory is required for motion vectors. 
FIG. 2 is a block diagram showing a conventional image reproduction 
apparatus for down-converting the MUSE signal to the NTSC signal. (See The 
Institute of Television Engineers of Japan journal, 1991, Vol. 45, No. 11, 
"5-2-3" "MUSE-NTSC Down-Converter", written by Yoshiki Mizutani and 
compiled by The Institute of Television Engineers of Japan.) In FIG. 2, 
numeral 101 designates an input signal processing circuit for subjecting 
the MUSE signal to input processing. The input signal processing circuit 
101 outputs the MUSE signal thus input processed to a time-axis conversion 
processing circuit 102 for converting the time axis from MUSE system to 
NTSC system. The time-axis conversion processing circuit 102 outputs the 
signal thus converted to a signal separation circuit 103 for separating it 
to be the luminance signal and the color difference signal from each 
other. The signal separation circuit 103 outputs the luminance signal (Y 
signal) to a Y scanning line conversion circuit 104 for converting 1125 
scanning lines to 525 scanning lines. The color difference signal is 
outputted to a time expansion circuit 105 for expanding the time axis by 
four times. The time expansion circuit 105 outputs the expanded color 
difference (C) signal to a color-difference vertical filter 106 for 
matching the expanded color difference signal with the converted Y 
scanning lines. The output signal of the Y scanning line conversion 
circuit 104 and the output signal of the vertical filter 106 are outputted 
to a vertical compression circuit 107 for further compressing the number 
of the converted scanning lines to 2/3. The output signals of the vertical 
compression circuit 107, the Y scanning line conversion circuit 104 and 
the color-difference vertical filter 106 are outputted to an input 
terminal of a 2-1 selector 108 for selecting one of two signals. The 
output side terminal of the 2-1 selector 108 is connected to an image 
processing circuit 109 for processing the converted signal in various 
ways. The image processing circuit 109 outputs an image-processed digital 
signal to a D/A converter 110 for converting the digital signal into an 
analog signal. The luminance signal and the color difference signal are 
outputted from the D/A converter 110 to a predetermined device. 
This conventional system further comprises a 16.2-MHz oscillator 112 as a 
MUSE system clock, a 14.742-MHz oscillator 113 which is a system clock 
having a conversion mode capable of maintaining the roundness with a 16:9 
monitor (hereinafter referred to as the full mode) and another conversion 
mode capable of maintaining the roundness by substantially total 
horizontal conversion with a 4:3 monitor (hereinafter referred to as the 
wide mode), and a 10.08-MHz oscillator 114 which is a system clock having 
still another conversion mode capable of maintaining the roundness with a 
4:3 monitor by discarding the horizontal conversion(hereinafter referred 
to as the zoom mode). The output signal of the 16.2-MHz oscillator 112 is 
outputted to an input signal processing circuit 101 and a time-axis 
conversion processing circuit 102. The 14.742-MHz oscillator 113 and the 
10.08-MHz oscillator 114 are connected to the input side terminal of a 2-1 
selector S.sub.18. The output side terminal of the 2-1 selector S.sub.18 
is in turn connected to the time-axis conversion processing circuit 102, 
the signal separation circuit 103, the Y scanning line conversion circuit 
104, the time expansion circuit 105, the color-difference vertical filter 
106, the vertical compression circuit 107 and the D/A converter circuit 
110. 
FIG. 3 is a block diagram showing the time-axis conversion processing 
circuit 102 of FIG. 2. The time-axis conversion processing circuit 102 
includes a line decision circuit 116 for outputting a decision signal on 
an odd- or even-numbered line by detecting lines from the MUSE signal, and 
time-axis conversion memories 117a, 117b for time-axis conversion from 
MUSE to NTSC signal. The time-axis conversion memory 117a is supplied with 
the output signal of the input signal processing circuit 101, an 
odd-numbered line signal from the line decision circuit 116, the output 
signal of the 16.2-MHz oscillator 112, and the output signal from the 
14.742-MHz oscillator 113 or the 10.08-MHz oscillator 114. The time-axis 
conversion memory 117a produces Y&R-Y in order an odd-numbered line. The 
time-axis conversion memory 117b is supplied with the output signal of the 
input signal processing circuit 101, an even-numbered line signal from the 
line decision circuit 116, the output signal from the 16.2-MHz oscillator 
112, and the output signal of the 14.742-MHz oscillator 113 or the 
10.08-MHz oscillator 114. The time-axis conversion memory 117b outputs 
Y&B-Y in an even-numbered line. 
FIG. 4 is a block diagram showing a specific example of the Y scanning line 
conversion circuit 104 shown in FIG. 2. The Y scanning line conversion 
circuit 104 includes fixed coefficient multipliers 118a, 118b for 
multiplying the fixed coefficient of the vertical filter for scanning line 
conversion and an adder 119. 
FIG. 5 is a block diagram showing a specific example of the vertical 
compression circuit 107 of FIG. 2. The vertical compression circuit 107 
includes two line memories 120 for delaying the input signal by one line, 
five fixed coefficient multipliers 118, adders 119a, 119b, a 2-1 selector 
S.sub.19, and a vertical compression memory 121. The adder 119a is 
supplied with a signal from a fixed coefficient multiplier 118, another 
signal through a line memory 120 and a fixed coefficient multiplier 118, 
and still another signal through two line memories 120 and a fixed 
coefficient multiplier 118. These signals are added by the adder 119a. The 
adder 119b is supplied with a signal through a fixed coefficient, 
multiplier 118 and another signal through a line memory 120 and a fixed 
coefficient multiplier 118, and these signals are added by the adder 119b. 
The adders 119a, 119b are connected to the input, side terminal of the 2-1 
selector S.sub.19. The vertical compression memory 121 is connected to the 
output side terminal of the 2-1 selector S.sub.19. 
Now, the operation will be explained. The inputted MUSE signal undergoes 
such processings as de-emphasis, control signal detection and PLL at the 
input signal processing circuit 101. The signal thus subjected to input 
processings is processed along time axis at the time-axis conversion 
processing circuit 102 shown in FIG. 3. More specifically, the signal thus 
subjected to input processings is divided into odd- and even-numbered 
lines and separately inputted to the time-axis conversion memories 117a, 
117b. In full or wide mode, for example, the 2-1 selector 108 selects the 
14.742-MHz oscillator 113 for converting the system clock to 14.742-MHz. 
In zoom mode, on the other hand, the 10.08-MHz oscillator 114 is selected 
to convert the system clock to 10.08-MHz. The signal converted along time 
axis is separated into the luminance signal and the color difference 
signal at the signal separation circuit 103. The luminance signal is 
inputted to the Y scanning line conversion circuit 104, and the color 
difference signal to the time expansion circuit 105. 
With regard to the luminance signal, the Y scanning line conversion circuit 
104 converts the number of MUSE effective scanning lines from 1032 to 516. 
In other words, one scanning line is produced from each two MUSE scanning 
lines. As shown in FIG. 4, in the Y scanning line conversion circuit 104, 
the odd- and even-numbered line signals separated by the signal separation 
circuit 103 and containing only the luminance signal component are 
inputted to the fixed coefficient multiplier circuits 118a, 118b 
respectively and multiplied by a predetermined fixed coefficient and added 
at the adder 119. FIG. 6 is a diagram showing the Y scanning conversion as 
a model at sampling points. As shown in FIG. 6, one scanning line is 
produced from each two scanning lines. In the case of FIGS. 4 and 5, the 
fixed coefficient is 1/2. Although the simplest example was explained 
above, the vertical filter (Y scanning line conversion circuit 104) for 
producing 516 scanning lines from 1032 scanning lines may double as a 
two-dimensional interpolation circuit in some cases in view of the fact 
that conversion with many scanning lines permits conversion with a minimal 
aliasing distortion. 
The color difference signal is transmitted with the MUSE signal compressed 
along time axis to 1/4 at the signal separation circuit 103 and therefore 
is time expanded by four times at the time expansion circuit 105. In case 
of the block diagram under consideration, two time expansion circuits are 
required for processing the odd-numbered line color difference signal and 
the even-numbered line color difference signal separately from each other. 
The color difference signal thus expanded along time axis is filtered for 
matching the vertical position with the scanning line of the luminance 
signal through a color difference signal vertical filter. The color 
difference signals are transmitted at intervals of 516 scanning lines. 
Therefore, the scanning lines are not, changed, but each color difference 
signal is filtered separately to assure vertical phase coincidence between 
the luminance signal and the color difference signal. The luminance signal 
converted in scanning lines or the color difference signal whose the 
vertical phase coinciding with the luminance signal is selected at the 2-1 
selector 108, and through the image processing circuit 109, given to the 
D/A converter 110 in full or zoom mode. 
In wide mode, the effective vertical scanning lines are converted to 2/3 by 
the vertical compression circuit 107. FIG. 7 is for explaining the 
vertical compression at the vertical compression circuit 107 with 
reference to a model at sampling points. As shown in FIG. 5, after 
delaying operation at a line memory 120, a three-line adder 119a and a 
two-line adder 119b are switched by the 2-1 selector S.sub.19 thereby to 
produce two scanning lines from three scanning lines. Every signal passing 
through each line is multiplied by a fixed coefficient at the fixed 
coefficient multiplier 118. The fixed coefficient of the fixed coefficient 
multiplier 118 shown in FIG. 5 is the same 1/2 for the lower two units 
using two lines, while the corresponding figures for the upper three units 
using three lines are differentiated at 1/4, 1/2 and 1/4 respectively. The 
effective scanning lines cannot be reduced to 2/3 simultaneously but the 
vertical conversion to 2/3 can be effected by sequential output of the 
calculation results after being temporarily stored in the vertical 
compression memory 121. In the configuration shown in FIG. 2, the circuit 
of FIG. 5 is required for each of the luminance signal and the color 
difference signal. 
The signals thus converted in full, zoom or wide mode are converted into an 
analog signal at the D/A converter 110 after undergoing image processing 
such as contour correction at the image processing circuit 109. 
The conventional image reproduction apparatus for down-converting the MUSE 
signal to the NTSC signal as shown in FIG. 2 is configured as described 
above. In full and zoom modes, the number of the elective scanning lines 
of the MUSE signal is converted from 1032 to 516. The monitor for 
receiving the signal having been converted to the NTSC signal is capable 
of displaying only 483 lines which is the number of effective scanning 
lines smaller than 516. As a result, the top and bottom formation on the 
screen disappear. In wide mode, therefore, another scanning line 
conversion circuit is required. Further, a scanning line conversion 
circuit and a vertical filter are required for the luminance signal and 
the color difference signal respectively, thereby leading to the problem 
of an increased circuit size. 
Also, three memories are required for time-axis conversion and vertical 
compression. The requirement of two system clock oscillators in full, wide 
and zoom mode poses the problems not only of a higher cost due to an 
increased circuit size but also of the adverse effect that high harmonics 
with a plurality of system clock frequencies and a beat signal have on the 
TV tuner circuit, etc. 
SUMMARY OF THE INVENTION 
The present invention has been devised in order to obviate the 
above-mentioned problems, and an object thereof is to provide an image 
reproduction apparatus for performing processes including sampling 
frequency conversion from a first frequency (32.4-MHz) to a second 
frequency (24.3-MHz), interfield interpolation at a third frequency 
(48.6-MHz) and sampling frequency conversion from the third frequency 
(48.6 MHz) to the first frequency (32.4-MHz), using linear interpolation 
or zeroth-order holding means, with the result that the interfield 
interpolation is made possible at the first frequency (32.4-MHz). Also, 
the motion vector requirement is met by the use of a first-in first-out 
memory and a line memory of at least six lines. 
The above and further objects and features of the invention will more fully 
be apparent from the following detailed description with accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the invention will be described below in detail with 
reference to the accompanying drawings. 
Embodiment 1: 
FIG. 8 is a block diagram showing a configuration of an image reproduction 
apparatus according to the invention. The shown case is a high definition 
TV receiver. In FIG. 8, numeral 1 designates an input processing section 
for performing such processings as de-emphasis of the MUSE signal or 
control signal detection. The input processing section 1 outputs the MUSE 
signal thus processed to a frame memory 2, an interframe interpolation 
circuit 3, a two-dimensional interpolation circuit 8 and a motion 
detection circuit 11. The frame memory 2 delays the video period of the 
MUSE signal processed in the input processing section 1 by one frame, and 
outputs the MUSE signal thus delayed to the interframe interpolation 
circuit 3 and the motion detection circuit 11. The interframe 
interpolation circuit 3 interpolates the signals at the two ends of the 
frame memory 2, and outputs tile processed signal to an LPF circuit 4. The 
LPF circuit 4 subjects the output of the interframe interpolates circuit 3 
to a 12-MHz low-pass filtering. The signal thus filtered is outputted to a 
field memory 6 and a 32.4-MHz interfield interpolation circuit 27. The 
field memory 6 delays the output of the LPF circuit 4 by one field and 
outputs it to the 32.4-MHz field interpolation circuit 27. The 32.4-MHz 
interfield interpolation circuit 27 interpolates the signals at the two 
ends of the field memory 6, and outputs the resulting signal to a mixer 
circuit 12. 
The two-dimensional interpolation circuit two-dimensionally interpolates 
the signal from the input processing section 1 in the field dimension, and 
outputs the processed signal to a delay circuit 29. The delay circuit 29 
delays the output of the two-dimensional interpolation circuit 8 by the 
amount of delay in the 32.4-MHz interfield interpolation circuit 27, and 
outputs the delayed signal to the mixer circuit 12. Numeral 10 designates 
a motion detection memory for delaying the video period of the MUSE signal 
by at least one frame. The motion detection circuit 11 detects a motion 
area from the outputs of the input processing section 1, the frame memory 
2 and the memory 10, and outputs the signal thus detected to the mixer 
circuit 12. The mixer circuit 12 mixes the still image processing signal 
output of the 32.4-MHz interfield interpolation circuit 27 with the moving 
image processing signal output of the delay circuit 29 in accordance with 
the detection signal from the motion detection circuit 11. 
FIG. 9 is a block diagram schematically showing the 32.4-MHz interfield 
interpolation circuit 27. The 32.4-MHz interfield interpolation circuit 27 
includes a sampling frequency conversion circuit 27a for performing the 
sampling frequency conversion from 32.4-MHz to 24.3-MHz by linear 
interpolation approximation, an interfield interpolation circuit 27b for 
performing interfield interpolation at 48.6 MHz by linear interpolation 
approximation, and a sampling frequency conversion circuit 27c for 
performing the sampling frequency conversion from 48.6-MHz to 32.4-MHz by 
linear interpolation approximation. 
FIG. 10 is a diagram for explaining a model of sampling points in the 
process of arithmetic operation at the 32.4-MHz interfield interpolation 
circuit 27 described above. In the diagram, alphabetical characters in 
squares denote sampling points of a first field, and those in circles 
sampling points of a second field. The hatched squares and circles 
represent the result of linear interpolation of the sampling frequency 
conversion. The triangular points represent the result, of linear 
interpolation of the 48.6-MHz sampling frequency conversion. The black 
circle designates the final output of the 32.4-MHz interfield 
interpolation circuit 27. 
Now, the operation will be explained. The MUSE signal inputted to the input 
processing section 1 is subjected to such input processings as de-emphasis 
and control signal detection. The MUSE signal thus subjected to input 
processings is processed separately for moving and still images, and the 
resulting signals are mixed at the mixer circuit 12. 
First, the still image processing is performed in such a manner that the 
output of the input processing section 1 is delayed by one frame at the 
frame memory 2, and the signals at the two ends of the frame memory 2 are 
temporally interpolated by the interframe interpolation circuit 3. The 
signal thus interframe-interpolated, which has a sampling frequency of 
32.4-MHz, contains an aliasing component of 12 MHz or more. In order to 
remove this aliasing component, the signal is subjected to low-pass 
filtering at 12-MHz by the LPF circuit 4. The output of the LPF circuit 4 
undergoes a sampling frequency conversion to 24.3-MHz at the sampling 
frequency conversion circuit 5. For conversion from 32.4-MHz to 24.3-MHz, 
the signal of 32.4-MHz is zeroth-order interpolated into 97.2-MHz, and 
subsampled at 24.3 Mhz. The signal thus frequency-converted to 24.3-MHz is 
delayed by one field at the field memory 6. The input and output signals 
of the field memory 6 are interpolated at the 48.6-MHz interfield 
interpolation circuit 7. The interfield interpolation requires a 
two-dimensional filtering in view of the reproduction range of the MUSE 
signal. 
In the moving image processing, on the other hand, the signal subjected to 
input processing at the input processing section 1 is two-dimensionally 
interpolated at the two-dimensional interpolation circuit 8. This output, 
which has a sampling frequency of 32.4-MHz, is converted to 48.6-MHz at 
the sampling frequency conversion circuit 9 in order to match with the 
final sampling frequency for still image processing. In the conversion 
from 32.4-MHz to 48.6-MHz, in the same way as in the processing at the 
sampling frequency conversion circuit 5, the 32.4-MHz frequency is 
zeroth-order interpolated to 97.2-MHz, and the resulting signal is 
subsampled at 48.6-MHz. 
The motion detection circuit 11 for mixing the still image processing and 
the moving image processing detects a motion area from the output of the 
frame memory 2 and the output of the memory 10 capable of delaying one 
frame or more. Normally, a motion area is detected by using a one frame 
difference signal subjected to 4-MHz low-pass filtering, a two-frame 
difference signal and the same two-frame difference signal delayed by one 
frame. A motion vector signal is detected from the control signal 
multiplexed on the MUSE signal at the input processing section 1. A 
dedicated memory is used for handling horizontal and vertical motion 
vectors at the motion detection circuit 11, the interframe interpolation 
circuit 3 and the 48.6-MHz interfield interpolation circuit 7. 
The motion area information detected at the motion detection circuit 11 is 
used to mix the output of the 48.6-MHz interfield interpolation circuit 7 
subjected to the still image processing with the output of the sampling 
frequency conversion circuit 9 subjected to the moving image processing at 
the mixer circuit 12. 
The output signal of the LPF circuit 4 and the same signal delayed by one 
field at the field memory 6 are inputted to the 32.4-MHz interfield 
interpolation circuit 27. These two signals are processed as shown in FIG. 
10 to provide a 32.4-MHz interfield-interpolated signal. The first 
sampling frequency conversion, the interfield interpolation and the second 
sampling frequency conversion are executed according to the linear 
interpolation means shown in the schematic block diagram of FIG. 9, with 
the result that a 32.4-MHz interfield-interpolated signal is synthesized. 
First, the signal applied to the 32.4-MHz sampling frequency conversion 
circuit 27a is designated by the alphabetical characters in the squares 
and circles in FIG. 10. The sampling frequency is 32.4-MHz. The linear 
interpolation approximation of the sampling frequency conversion of this 
signal from 32.4-MHz to 24.3-MHz at the sampling frequency conversion 
circuit 27a is performed in the following manner. Specifically, as shown 
in FIG. 10, B is reduced to 2/3 and C to 1/3 and they are added to perform 
linear interpolation, thereby approximating the 24.3-MHz sampling point 
denoted by the hatched square between points B and C. Now, the linear 
Interpolation approximation of the 48.6-MHz interfield interpolation at 
the interfield interpolation circuit 27b shown in FIG. 9 is performed in 
the following manner. Specifically, this approximation process is 
performed in such a manner that the 24.3-MHz sampling points designated by 
a hatched square and circle in FIG. 10 are linearly interpolated or 
averaged between two nearest interfield points. The result is the sampling 
points interfield-interpolated at 48.6-MHz as denoted by triangles. 
Finally, the sampling Frequency conversion from 48.6-MHz to 32.4-MHz is 
effected at the sampling frequency conversion circuit 27c in FIG. 9 in the 
following manner. Specifically, this approximation is represented by the 
very sampling point interfield-interpolated at 48.6-MHz or the average of 
two sampling points as shown in FIG. 10. 
The arithmetic operations at these circuits 27a, 27b, 27c are not effected 
each time, but may be performed by advance calculations in several stages 
through the operation with a 32.4-MHz clock alone. The point indicated by 
the black circle 2 in FIG. 10, for example, can be represented as 
a/6+2.times.b/6+2.times.B/6+C/6, and that indicated by the black circle 3 
as c/2+B/6+C/6+D/6. In this case, only these two types of coefficients are 
used for basic arithmetic operation, provided that the same arithmetic 
operation is performed for four horizontal samples and the phase change in 
field subsampling. As a result, the 32.4-MHz interfield interpolation is 
realized by controlling a very simple arithmetic circuit by a field 
subsampling along horizontal direction. 
In the explanation above, the simplest linear interpolation between two 
points was employed. When the approximation by linear interpolation at 
more sampling points is used for calculations of sampling frequency 
conversion from 32.4 MHz to 24.3-MHz, interfield interpolation at 48.6-MHz 
and the sampling frequency conversion from 48.6-MHz to 32.4-MHz, however, 
the degradation of the frequency characteristics is reduced in spite of a 
somewhat increased size of the arithmetic circuit for the approximation. 
Another example of the embodiment will be explained. FIG. 11 shows a model 
of sampling points for explaining the 48.6-MHz interfield interpolation at 
the 32.4-MHz interfield interpolation circuit 27 according to this 
embodiment, which is performed using another means. In this embodiment, 
the field-delayed signal is delayed by a line memory, and the signals 
before and after the delay are averaged for sampling conversion and 
embedded in the middle after sampling conversion of the signal before 
field delay, thereby performing the 48.6-MHz sampling frequency 
conversion. According to this method, the filters along horizontal 
direction are decreased by one so that the degradation of the horizontal 
resolution is suppressed for achieving linear approximation. Since a line 
memory is required, however, the circuit size is increased. 
Embodiment 2: 
Now, an embodiment 2 (claim 2) will be explained. Explanation will be made 
only about a 32.4-MHz interfield interpolation circuit 27 which is 
different from the embodiment 1. The general configuration of the high 
definition TV receiver according to the embodiment 2 is similar to that of 
the embodiment 1 (FIG. 8) and therefore will not be described further. 
FIG. 12 is a block diagram schematically showing the 32.4-MHz interfield 
interpolation circuit 27 according to the embodiment 2. This circuit 
includes a sampling frequency conversion circuit 27d for converting the 
sampling frequency from 32.4-MHz to 24.3-MHz by approximation with 
zeroth-order holding or the nearest sample, an interfield interpolation 
circuit 27b and a sampling frequency conversion circuit 27c similar to the 
corresponding component parts in the embodiment 1. 
FIGS. 13 and 14 are diagrams for explaining the arithmetic operation of the 
32.4-MHz interfield interpolation circuit 27 according to this embodiment 
with reference to a model of sampling points. The diagram of FIG. 13 
corresponds to the case in which the sampling frequency conversion from 
32.4-MHz to 24.3-MHz is approximated by zeroth-order holding, and FIG. 14 
the case in which the sampling frequency conversion from 32.4-MHz to 
24.3-MHz is approximated by the nearest sample. In FIGS. 13 and 14, the 
alphabetical characters in squares represent sampling points in a first 
field, and those in circles sampling points in a second field. The hatched 
squares and circles indicate the result of approximation of the sampling 
frequency conversion by zeroth-order holding or with the nearest sample. 
The triangular points represent the result of linear interpolation of the 
48.6-MHz sampling frequency conversion. The black circle represents the 
final output of the 32.4-MHz interfield interpolation circuit 27. 
Now, the operation will be explained. The signal inputted to the 32.4-MHz 
interfield interpolation circuit 27, which is indicated by the 
alphabetical characters in circles and squares in FIGS. 13 and 14, has a 
sampling frequency of 32.4-MHz. In the approximation by zeroth-order 
holding of the sampling frequency conversion from 32.4-MHz to 24.3-MHz 
effected at the sampling frequency conversion circuit 27d, as shown in 
FIG. 13, four points A, B, C, D are approximated by three 24.3-MHz points 
A, B, C. According to the approximation by the nearest sample, on the 
other hand, as shown in FIG. 14, the four points A, B, C, D are 
approximated by the three 24.3-MHz points A, B, C. In the approximation by 
the 48.6-MHz interfield linear interpolation at the interfield 
interpolation circuit. 27b shown in FIG. 12, on the other hand, the 
24.3-MHz sampling points designated by hatched squares and circles in 
FIGS. 13 and 14 are linearly interpolated or averaged between the nearest 
two interfield points. Thus the sampling points subjected to 48.6-MHz 
interfield interpolation are obtained as indicated by triangles. Finally, 
the sampling frequency conversion from 48.6 MHz to 32.4-MHz at the 
sampling frequency conversion circuit 27c shown in FIG. 12 is performed, 
as shown in FIGS. 13 and 14, are represented by the very sampling point 
subjected to 48.6-MHz interfield interpolation or the average of two 
sampling points as shown in FIGS. 13 and 14. 
When the arithmetic operation at these circuits 27d, 27b, 27 c is not 
performed each time but in advance, the calculation can be performed in 
several stages by the operation with only 32.4-MHz clocks. In FIG. 13, the 
point represented by black circle 2, for example, is expressed as a/2+B/2, 
and the point of black circle 3 as c/2+B/4+C/4. Also, in FIG. 14, the 
point of black circle 2 is given as b/2+B/2, and the point of black circle 
3 as c/2+B/4+D/4. In this case, the coefficients for basic arithmetic 
operation are limited to these two types, with the result, that the same 
arithmetic operation is used for four horizontal samples and the field 
subsample phase is changed. The result is a very simple arithmetic 
operation circuit, which is controlled by horizontal field subsampling 
thereby to realize a 32.4-MHz interfield interpolation. 
Although the explanation above employs the simplest linear interpolation 
between two points, a calculation made in advance for linear interpolation 
approximation of the 48.6-MHz interfield interpolation and the sampling 
frequency conversion from 48.6-MHz to 32.4-MHz at more sampling points 
makes possible an approximation accompanied by a small degradation of the 
frequency characteristics at the cost of a somewhat increased size of the 
arithmetic circuit. 
The zeroth-order holding process and the use of the nearest sample lead to 
the same arithmetic equation in applications to an interfield 
interpolation circuit in spite of different sampling points since the 
filters of the same characteristics are used for the two operations. 
Embodiment 3: 
Now, an embodiment 3 (claims 3 and 4) will be explained. Explanation will 
be limited to the 32.4-MHz interfield interpolation circuit 27 different 
from the embodiment 1. The general configuration of the high definition TV 
receiver according to the embodiment 3 is similar to that of the 
embodiment 1 (FIG. 8), and therefore will not be described further. 
FIG. 15 is a block diagram schematically showing the 32.4-MHz interfield 
interpolation circuit 27 according to the embodiment 3. This 32.4-MHz 
interfield interpolation circuit 27 includes a sampling frequency 
conversion circuit 27e for converting the sampling frequency from 32.4-MHz 
to 24.3-MHz by the approximation using zeroth-order holding, the nearest 
sample or the linear interpolation, an interfield interpolation circuit 
27b similar to the embodiment 1, and a sampling frequency conversion 
circuit 27f for converting the sampling frequency from 48.6-MHz to 
32.4-MHz by approximation in zeroth-order holding. 
FIG. 16 is a diagram for explaining the arithmetic operation of the 
32.4-MHz interfield interpolation circuit 27 with reference to a model of 
sampling points. In FIG. 16, the alphabetical characters in squares denote 
the sampling points in a first field, and those in circles the sampling 
points in a second field. The hatched squares and circles represent the 
result of zeroth-order holding of the sampling frequency conversion. The 
triangular points represent the result of linear interpolation of the 
48.6-MHz sampling frequency conversion. The black circle obtained by 
zeroth-order holding the above-mentioned sampling frequency conversion 
represents the final output of the 32.4-MHz interfield interpolation 
circuit 27. 
Now, the operation will be explained. The signal inputted to the 32.4-MHz 
interfield interpolation circuit 27 is represented by the alphabetical 
characters in squares and circles in FIG. 16. The sampling frequency is 
32.4-MHz. The sampling frequency conversion of this signal from 32.4-MHz 
to 24.3-MHz at the sampling frequency conversion circuit 27e is 
approximated by zeroth-order holding in such a manner that four points A, 
B, C, D are approximated by three 24.3-MHz points A, B, C as shown in FIG. 
16. Then, the approximation by the 48.6-MHz interfield linear 
interpolation at the interfield interpolation circuit 27b in FIG. 15 is 
performed in such a manner that the 24.3-MHz sampling points in hatched 
squares and circles in FIG. 16 are linearly interpolated or averaged 
between two nearest interfield points. Then, sampling points subjected to 
48.6-MHz interfield interpolation are obtained as indicated by triangles. 
Finally, the sampling frequency conversion from 48.6-MHz to 32.4-MHz in 
the sampling frequency conversion circuit 27f in FIG. 15 is performed, as 
shown in FIG. 16, by zeroth-order holding the sampling points subjected to 
interfield interpolation at 48.6-MHz. 
When the arithmetic operations of these circuits 27e, 27b, 27f are not 
effected each time, but calculations beforehand desirably limit the 
arithmetic operation to several stages only with 32.4-MHz clocks. The 
point at black circle 2 in FIG. 16, for example, is expressed as a/2+B/2, 
and the point of black circle 3 as B/2+c/2. In the shown case, the 
coefficients for the basic calculations are limited to these two types, 
with tile result that the phase undergoes a change with a field 
subsampling and the same arithmetic operation is involved for each four 
samples in horizontal direction. The resulting provision of a very simple 
arithmetic circuit, which is controlled by field subsampling along 
horizontal direction, can realize a 32.4-MHz interfield interpolation. 
Although the linear interpolation between two points which is simplest has 
been explained in the foregoing description, advance calculations for 
approximation by 48.6-MHz linear interfield interpolation at more sampling 
points permits an approximation with a smaller degradation in frequency 
characteristics in spite of a somewhat increased size of the arithmetic 
circuit. 
Embodiment 4: 
Now, an embodiment 4 (claims 5 and 6) will be explained. Explanation will 
be limited to the 32.4-MHz interfield interpolation circuit 27 different 
from the embodiment 1. The general configuration including other component 
parts of the high definition TV receiver according to the embodiment 4 is 
similar to that of the embodiment 1 (FIG. 8), and will not be explained 
further. 
FIG. 17 is a block diagram schematically showing the 32.4-MHz interfield 
interpolation circuit 27 according to the embodiment 4. The 32.4-MHz 
interfield interpolation circuit 27, includes a sampling frequency 
conversion circuit. 27e being the same one as in the embodiment 4 and an 
interfield-interpolation/sampling frequency conversion circuit 27g for 
approximating the interfield interpolation at 48.6 MHz and the sampling 
frequency conversion from 48.6-MHz to 32.4-MHz collectively by linear 
interpolation. 
FIG. 18 is a diagram for explaining the arithmetic operation of the 
32.4-MHz interfield interpolation circuit 27 according to the embodiment 4 
with reference to a model of sampling points. In FIG. 18, the alphabetical 
characters in squares designate sampling points in a first field, and 
those in circles sampling points in a second field. Also, the hatched 
squares and circles represent the result of zeroth-order holding of the 
sampling frequency conversion. The black circles representing the 
collective linear interpolation of the sampling frequency conversion from 
the zeroth-order held result to 48.6-MHz and from 48.6-MHz to 32.4-MHz is 
the final output of the 32.4-MHz interfield interpolation circuit 27. 
Now, the operation will be explained. The signal inputted to the 32.4-MHz 
sampling frequency conversion circuit 27 is designated by the alphabetical 
characters in the squares and circles in FIG. 18, the sampling frequency 
being 32.4-MHz. The approximation by the nearest sample of the sampling 
frequency conversion from 32.4-MHz to 24.3-MHz performed at the sampling 
frequency conversion circuit 27e is effected from four points A, B, C, D 
to three 24.3-MHz points A, B, C as shown in FIG. 18. Then, the 
approximation by collective linear interpolation of the 48.6-MHz 
interfield interpolation and the sampling frequency conversion from 
48.6-MHz to 32.4-MHz at the interfield interpolation/sampling frequency 
conversion circuit. 27g in FIG. 17 is performed by using the 24.3-MHz 
sampling points designated by hatched squares and circles in FIG. 18 
intact or by averaging the two points. 
The arithmetic operation for these circuits 27e, 27g may not be performed 
each time but calculations beforehand desirably limit the arithmetic 
operation to several stages only with the 32.4-MHz clocks. For example, 
the point of the black circle 2 is represented as b/2+B/2 and the point 
designated by the black circle 3 as c. In the shown case, this coefficient 
is the only one for basic arithmetic operations, and the approximation can 
be performed with the sole result that the calculation is made or a sample 
value obtained for each output sample and the field subsample undergoes a 
phase change. As a result, a very simple arithmetic circuit can be 
employed and controlled by a field subsample in horizontal direction 
thereby to realize a 32.4-MHz interfield interpolation. 
Although the linear interpolation between two points has been explained 
above as the simplest method an approximation with a small degradation of 
the frequency characteristics is possible in spite of a somewhat increased 
size in the arithmetic circuit, if calculations are made in advance For 
approximation by linear interpolation collectively at more sampling points 
for the 48.6-MHz interfield interpolation and the sampling frequency 
conversion from 48.6-MHz to 32.4-MHz. 
Embodiment 5: 
Now, an embodiment 5 (claim 7) will be explained. FIG. 19 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the fifth embodiment. In FIG. 19, the input processing 
section 1, the interframe interpolation circuit 3, the LPF circuit 4, the 
two-dimensional interpolation circuit 8, the memory 10, the motion 
detector circuit 11 and the mixer circuit 12 are identical to those 
described in the embodiment 1 respectively shown in FIG. 8 and will not be 
described again. Numeral 13 designates a field memory for delaying the 
input signal by one field. Numeral 14 designates a control signal 
generator circuit for generating a control signal for subsequent. stages 
from the signal of the input processing section 1 two-dimensionally 
interpolated by the two-dimensional interpolation circuit 8, a signal 
field-delayed at a field memory 13 and two-dimensionally interpolated at 
another two-dimensional interpolation circuit 8 and a signal frame-delayed 
by two series-connected field memories 13, 13 and two-dimensionally 
interpolated by still another two-dimensional interpolation circuit 8. 
Numeral 15 designates an adaptive mixer circuit for mixing the output of 
the interframe interpolation circuit 3 and the output of the 32.4-MHz 
interfield-interpolation circuit 27 shown in the embodiments 1-4 with each 
other adaptively by a control signal. 
Now, the operation will be explained. The signal subjected to input 
processings at the input processing section 1 is delayed by one frame at 
the two field memories 13, 13, and the signals before and after the delay 
are subjected to interframe interpolation at the interframe interpolation 
circuit 3. Also, the input-processed signal and the signal field-delayed 
at the field memories 13 are two-dimensionally interpolated at the 
two-dimensional interpolation circuits 8 respectively, and these signals 
are band-limited to 12-MHz at the LPF circuits 4, 4. The two signals thus 
band-limited are subjected to interfield interpolation at the 32.4-MHz 
interfield interpolation circuit 27 shown in the embodiments 1.about.4. Of 
the signals thus interpolated, the interframe-interpolated signal contains 
a field aliasing component, and the interfield-interpolated signal a frame 
aliasing component. As far as one of the two signals is used as a signal 
for still image processing, therefore, the frame or field aliasing 
component is visible as an interference in the still image. 
In order to obviate this interference, first, three signals are generated: 
One by two-dimensionally interpolating the output of the input processing 
section i at the two-dimensional interpolation circuit 8, a second signal 
by field-delaying the output of the input processing section 1 at the 
field memories 13, 13 anti two-dimensionally interpolating them at the 
two-dimensional interpolation circuit 8, and the last signal by 
frame-delaying the output of the input processing section 1 at the two 
series-connected field memories 13, 13 and two-dimensionally interpolating 
them at the two-dimensional interpolation circuit 8. These three 
two-dimensionally interpolated signals are compared in magnitude, for 
example, for each sample at the control signal generator circuit 14, so 
that the frame or field aliasing component is decided on thereby to 
generate a control signal. An adaptive mixer circuit 15 is used, in which 
the signal synthesis ratio is changed adaptively according to the 
interframe or interfield interpolation by performing the interframe or 
interfield interpolation in the presence of a frame or field aliasing 
component respectively. This mixer circuit 15 is thus used for mixing with 
a moving image processing signal. In this way, the above-mentioned 
interference is prevented, and with a performance equivalent to the 
configuration shown in the embodiment 1 (FIG. 8), the number of field 
memories can be saved as compared with the embodiment shown FIG. 8, 
thereby reducing the system cost. 
Embodiment 6: 
Now, an embodiment 6 (claim 8) will be explained. FIG. 20 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 6. In FIG. 20, the LPF circuit 4 of the fifth 
embodiment in FIG. 19 is eliminated, and instead, a two-dimensional 
interpolation circuit 18 identical to or different from the 
two-dimensional interpolation circuit 8 in FIG. 19 is inserted at the 
output of the input processing section 1 and the field memory 13 
respectively. 
Now, the operation will be explained. The components of 12-MHz or higher, 
when not removed from the input of tile 32.4-MHz interfield interpolation 
circuit 27, are undesirably reproduced as an aliasing after interfield 
interpolation. In view of this, in case of FIG. 19, the 12-MHz LPF circuit 
4 is inserted to attenuate the components of 12-MHz or higher. 
According to the embodiment 6 under consideration (FIG. 20), in contrast, 
the two-dimensional interpolation circuit 18 has a filtering 
characteristic making the components of 12-MHz or higher as a cut-off 
region. Without the LPF circuit 4 shown in FIG. 19, therefore, the 
aliasing components of 12-MHz or higher can be suppressed. Strictly, the 
12-MHz attenuation characteristic is required to be complementary with the 
characteristic on the encoder side. However, this would result in a large 
LPF circuit. An LPF circuit which cannot have such a complementary 
characteristic would be an extraneous circuit. By attenuating the 12-MHz 
or higher frequency components at the two-dimensional interpolation 
circuit 18, therefore, the most part of the aliasing components can be 
suppressed with a reduced circuit size. 
Although not described in detail in this invention, the signal 
two-dimensionally interpolated from the present signal and each delayed 
signal through a two-dimensional interpolation circuit is used normally in 
the motion detection circuit 11. The two-dimensional interpolation circuit 
can therefore double as a motion detection circuit by appropriate circuit 
design. 
Embodiment 7: 
Now, an embodiment 7 (claim 9) will be explained. FIG. 21 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 7. In FIG. 21, a vertical filter 16 is added 
in series to the two-dimensional interpolation circuit 18 for 
two-dimensionally interpolating the signal delayed through the field 
memory 13 in FIG. 20 of the embodiment 6. The output of the vertical 
filter 16 is connected to a control signal generator circuit 15 and a 
32.4-MHz interfield interpolation circuit 27. 
The operation of the embodiment 7 will be explained. The signal processed 
at the input, processing section 1 and the signal frame-delayed the two 
series-connected field memories 13 and 13 two-dimensionally interpolated 
at the two-dimensional interpolation circuit 18 have uniform vertical and 
horizontal positions. The signal field-delayed at one field memory 13 and 
two-dimensionally interpolated at the two-dimensional interpolation 
circuit 18, however, is displaced by one line in vertical direction due to 
the interlace. When a one-frame difference and a one-field difference are 
determined to generate a control signal by comparison under this 
condition, a faulty operation would be likely to occur for signals of high 
vertical frequencies. 
The faulty operation at high vertical frequency signals can be reduced by 
matching the vertical position of the signal field-delayed at the one 
field memory 13 and two-dimensionally interpolated with that of the 
remaining two signals through a vertical filter 16. The simplest example 
of the vertical filter can be realized by inserting a line memory in 
series to the two-dimensional interpolation circuit 18 and adding the 
signals at the two ends of the line memory. The use of more line memories 
complicating coefficients can further reduce the faulty operations. 
Embodiment 8: 
Now, an embodiment 8 (claim 10) will be explained. FIG. 22 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 8. The embodiment 8 (FIG. 22) which is 
configured substantially the same way as the embodiment 6 (FIG. 20) 
comprises a two-dimensional interpolation circuit 28 including at least 
one more line memory than the two-dimensional interpolation circuit 18 for 
two-dimensionally interpolating the other present signal and the 
frame-delayed signal, which circuit 28 two-dimensionally interpolates the 
signal field-delayed at the field memory 13. 
Now, the operation of this embodiment 8 will be explained. As described 
with reference to the embodiment 7, in the case where the signal 
two-dimensionally interpolated from the present signal and the 
frame-delayed signal and a field-delayed signal, are two-dimensionally 
interpolated at the same two-dimensional interpolation circuit. 18 the 
control signal is liable to cause a faulty operation at high vertical 
frequency signal. 
According to the embodiment 8, the two-dimensional interpolation circuit 28 
including at least one or more line memories than the other 
two-dimensional interpolation circuits 18 is used in two-dimensionally 
interpolating the signal field-delayed at the field memory 13. In this 
way, the same vertical position is secured as the other two-dimensionally 
interpolated signals, thereby reducing the faulty operation of the control 
signal at high vertical frequencies. This function is equivalent to that 
of the embodiment 7 using the vertical filter 16. The embodiment under 
consideration, however, is further reduced in circuit size as compared 
with the embodiment using the vertical filter 16. 
Embodiment 9: 
Now, an embodiment 9 (claim 11) will be explained. FIG. 23 is an internal 
block diagram of the control signal generator circuit 14 according to the 
embodiments 7 and 8 (FIGS. 21, 22). In FIG. 23, numeral 14a designates a 
subtractor for subtracting one signal from the other of two signals 
according to the sign attached to them, and numeral 14b a comparison ROM 
for outputting a control signal or the output of the subtractor 14a. 
The operation of the embodiment 9 will be explained. 
The present signal processed in the input processing section 1, the signal 
field-delayed at the field memories 13, 13 and the signal frame-delayed, 
as shown in the embodiments 7 and 8, are supplied to the control signal 
generator circuit 14, the present signal and the frame-delayed signal as 
two-dimensionally interpolated at the same two-dimensional interpolation 
circuit 18, and the field-delayed signal as a two-dimensionally 
interpolated signal with uniform vertical phase. These three signals are 
grouped into two signals including a frame difference signal obtained by 
subtracting the two-dimensionally interpolated present signal from the 
frame-delayed two-dimensionally interpolated signal at a subtractor 14a 
and a field difference signal obtained by subtracting the 
two-dimensionally interpolated present. signal from the field-delayed 
two-dimensionally interpolated signal at another subtractor 14a, the 
resulting two signals being inputted to the comparison ROM 14b. Since the 
field difference signal and tile frame difference signal obtained by 
subtraction at the subtractor 14a, 14b are inputted to the comparison ROM 
14b, the difference between the two difference signals is present in the 
vicinity of zero due to the characteristics of a video signal, and 
therefore the comparison ROM 14b can be reduced in size. The use of the 
comparison ROM 14b thus facilitates generation of a control signal. 
Embodiment 10: 
Now, an embodiment 10 (claim 12) will be explained. FIG. 24 is an internal 
block diagram showing the control signal generator circuit 14 according to 
the embodiments 7 and 8 (FIGS. 21, 22). In FIG. 24, numeral 14a designates 
a subtractor for subtracting one signal from the other of two signals in 
accordance with the sign, numeral 14c an absolute value circuit for 
determining the absolute value of the output of the subtractor 14a, and 
numeral 14d a comparator for comparing the output of the absolute value 
circuit 14c with an externally-settable arbitrary value. 
The operation of this embodiment will be explained. The frame difference 
signal obtained by subtracting the two-dimensionally interpolated present 
signal from the frame-delayed two-dimensionally interpolated signal at a 
subtractor 14a and the field difference signal obtained by subtracting the 
two-dimensionally interpolated present signal from the field-delayed 
two-dimensionally interpolated signal at the other subtractor 14a are 
converted into absolute values at the absolute value circuits 14c 
respectively. Each of the outputs of the absolute value circuits 14c is 
compared with an externally-settable arbitrary value at each comparator 
14d. The output of these comparators 14d is used as a control signal. By 
setting one input to the comparator 14d as an externally-settable 
arbitrary value, in the event that the ratio of the MUSE input signal is 
low, for instance, the arbitrary set value used for comparison with the 
field difference signal can be changed. In this way, the control signal is 
generated in such a manner as not to mix the output of the 32.4-MHz 
interfield interpolation circuit 27 as far as possible, and the apparent 
ratio of the final output can thus be improved. 
In the embodiment 9 described above, a similar effect is attained by 
switching the outputs of several ROMs in parallel by means of a selector 
in response to an external signal or by switching the most significant 
bits of the ROM in response to an external signal. 
Embodiment 11: 
Now, an embodiment 11 (claim 13) will be explained. FIG. 25 is an internal 
block diagram showing the control signal generator circuit 14 according to 
the embodiments 7 and 8 (FIGS. 21, 22). In FIG. 25, numeral 14a designates 
a subtractor for subtracting one from the other of two signals in 
accordance with the sign, numeral 14e a horizontal HPF for horizontal 
high-pass filtering the field difference signal, numeral 14c absolute 
value circuits for determining the absolute value of the outputs of the 
subtractors 14a, and numeral 14d a comparator for comparing the output of 
each absolute value circuit 14c with an externally-settable arbitrary 
value. 
The operation of the embodiment 11 will be explained. According to the 
ninth and embodiments 10, the field difference signal is adjusted in 
vertical phase by two-dimensionally interpolating of a field-delayed 
signal and applying the resulting signal to a vertical filter or by the 
use of a two-dimensional interpolation circuit having at least one more 
line. The field difference thus becomes conspicuous at high vertical 
frequencies and distinction from the horizontal high-frequency components 
is difficult. In order to solve this problem, the field difference signal 
is applied to the horizontal HPF 14e to remove the horizontal 
low-frequency component from the vertical high-frequency components. The 
control signal is thus easily generated at the comparator 14d (or the 
comparison ROM 14b). 
Embodiment 12: 
Now, an embodiment 12 (claim 14) will be explained. FIG. 26 is an internal 
block diagram showing the control signal generator circuit 14 according to 
the embodiments 7 and 8 (FIGS. 21, 22). In FIG. 26, numeral 14f designates 
a control signal generator circuit shown in the embodiments 9-11, and 
numeral 14g a horizontal expansion circuit for expanding the output of the 
control signal generator circuit 14f in horizontal direction. 
The operation of this embodiment will be explained. The output of the 
control signal generator circuit shown in the embodiments 9-11 is produced 
in sample units, i.e., in units of 32.4-MHz. In the case where horizontal 
high-frequency components are existent in succession, for instance, assume 
that comparison between the frame difference signal and the field 
difference signal shows the presence of the two and that at a minor level. 
The control signal is switched in units of 32.4-MHz, and therefore as 
described above, a field aliasing occurs in the interframe interpolation, 
and a frame aliasing in the interfield interpolation. As a result, when 
the control signal is switched in units of 32.4-MHz, the aliasing may be 
emphasized. In view of this, the control signal is expanded in horizontal 
direction and is fixed at either the interframe interpolation or the 
interfield interpolation for a predetermined period. The aliasing can thus 
be removed stably. 
Embodiment 13: 
Now, an embodiment 13 (claim 15) will be explained. FIG. 27 is an internal 
block diagram showing the control signal generator circuit 14 according to 
the embodiments 7 and 8 (FIGS. 21, 22). In FIG. 27, numeral 14f designates 
a control signal generator circuit shown in the embodiments 9-11, numeral 
14h a line memory having at least one line, numeral 14i a vertical 
correlation circuit for determining the vertical correlationship from the 
present signal or the field-delayed signal, and numeral 14j a vertical 
direction expanding circuit for enlarging the output of the control signal 
generator circuit, 14f in vertical direction. 
The operation of the embodiment 13 will be described. The control signal 
generator circuit 14f shown in the embodiments 9-11 is supplied with the 
two-dimensionally interpolated present signal, the field-delayed 
two-dimensionally interpolated signal and the frame-delayed 
two-dimensionally interpolated signal for generating a control signal. The 
control signal thus generated is delayed by at least one line and the 
vertical correlationship of the control signal is detected. When the 
correlationship is high, the control signal is expanded in vertical 
direction. In this way, when the ratio of the input signal is low, for 
example, the faulty operation which otherwise might be caused by the noise 
mixed in the field difference or frame difference signal is prevented by 
taking the line correlationship. The system performance can of course be 
improved by taking the correlationship with a greater number of line 
memories. 
Delaying the control signal through a line memory is equivalent to 
increasing the number of line memories. Since the circuit size is thus 
increased, the vertical correlationship can be determined from line delay 
in two-dimensionally interpolating the present signal. This process occurs 
before the two-dimensional interpolation, and therefore the output 
represents the correlationship between each two lines and a 16.2-MHz 
correlationship output. The problem, however, can be obviated by using the 
horizontal enlarging circuit shown in the embodiment 12. In similar 
fashion, the correlationship can be detected by the filed-delayed signal. 
In particular, the field-delayed signal contributes to the detection of 
the vertical correlationship in view of the many line memories due to the 
two-dimensional interpolation or vertical filter as shown in the 
embodiments 7, 8. 
Embodiment 14: 
Now, an embodiment 14 (claim 16) will be explained. FIG. 28 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 14. In FIG. 28, the input processing section 
1, the field memories 13, the two-dimensional interpolation circuit 18, 
the two-dimensional interpolation circuits 28 with many line memories, the 
control-signal generator circuit 14, the memory 10, the motion detection 
circuit 11, the 32.4-MHz interfield interpolation circuit 27 and the 
adaptive mixer circuit 15 are similar to the corresponding component parts 
in FIG. 22 (embodiment 8), and therefore will not be described further. 
Numeral 21 designates a double multiplier by bit shift, numeral 22 a 
subtractor for subtracting the two-dimensionally interpolated present 
signal from the output; of the multiplier 21, and numeral 23 a mixer 
circuit for mixing up to the average of the two-dimensionally interpolated 
present signal and the output of the adaptive mixer circuit 15 from the 
two-dimensionally interpolated present signal. 
The operation of this embodiment will be explained. According to the 
embodiment 8, the output of the interframe interpolation circuit 3 and the 
output of the 32.4-MHz interfield interpolation circuit 27 are mixed with 
each other at the adaptive mixer circuit 15. The control signal used for 
this mixing is generated at the control signal generator circuit 14 on the 
basis of the signal obtained by two-dimensionally interpolating the 
present signal, the field-delayed signal and the frame-delayed signal at 
the two-dimensional interpolation circuits 18, 28. For this reason, both 
the interframe interpolation circuit 3 and the two-dimensional 
interpolation circuit 18 for frame delay are required leading to an 
increased circuit size. According to the embodiment; 14, the interframe 
interpolation is performed in such a manner that the present signal and 
the frame-delayed signal are two-dimensionally interpolated at the 
two-dimensional interpolation circuit: 18, and are mixed with the 
two-dimensionally interpolated present signal up to the average between 
the two-dimensionally interpolated present signal and the frame-delayed 
two-dimensionally interpolated signal at the mixer circuit 23. The average 
between the two-dimensionally interpolated present signal and the 
frame-delayed two-dimensionally interpolated signal is equivalent to the 
signal obtained by interframe interpolation and two-dimensional filtering. 
The aliasing component of the frame can thus be removed. Nevertheless, the 
frequency characteristic is deteriorated by an amount corresponding to the 
two-dimensional filtering. This configuration reduces the circuit size 
thereby making possible of interframe interpolation. 
When the output of the 32.4-MHz interfield interpolation circuit 27 is used 
for a still image using the mixer circuit 23, the average is taken with 
the present signal. In the case where the output of the 32.4-MHz 
interfield interpolation circuit 27 is doubled and the present signal is 
subtracted, therefore, the output of the mixer circuit 23 becomes the 
32.4-MHz interfield-interpolated output with the average taken with the 
present signal. By the way, the average between the present signal and the 
output of the adaptive mixer circuit 25 is taken at the mixer circuit 23 
when a still image is detected by the motion detection circuit 11. 
Embodiment 15: 
Now, an embodiment 15 (claim 17) will be explained. FIG. 29 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 15. In FIG. 29 (embodiment 15), the difference 
from the embodiment of FIG. 28 (embodiment 14) lies in that the signal 
field-delayed at a field memory 13 and two-dimensionally interpolated at 
the two-dimensional interpolation circuit 28 with many line memories is 
inputted to the adaptive mixer circuit 25. 
Now, the operation will be explained. In the case where the signal 
field-delayed at the field memory 13 and two-dimensionally interpolated at 
the two-dimensional interpolation circuit 28 with many line memories is 
averaged with the signal two-dimensionally interpolated from the present 
signal, the field aliasing can be removed, although the horizontal 
high-frequency components cannot be removed. Taking advantage of this 
fact, the adaptive mixer circuit 25 is supplied with the 32.4-MHz 
interfield-interpolated signal doubled and subtracted from by the present 
two-dimensionally interpolated signal, the signal frame-delayed and 
two-dimensionally interpolated, and the field-delayed signal 
two-dimensionally interpolated. Further, the field-delayed 
two-dimensionally interpolated signal is inserted, while switching to the 
32.4-MHz interfield-interpolated signal doubled and subtracted from by the 
two-dimensionally interpolated present signal and the frame-delayed 
two-dimensionally interpolated signal As a result, the interframe 
interpolation can be smoothly switched to the interfield interpolation 
with substantially the same circuit size. 
Embodiment 16: 
Now, an embodiment 16 (claim 18) will be explained. FIG. 30 is a block 
diagram showing the configuration of a high definition TV receiver 
according the embodiment 16. In FIG. 30, the input processing section 1, 
the frame memory the interframe interpolation circuit, 3, the 
two-dimensional interpolation circuit 18, the memory 10, the motion 
detection circuit 11, the LPF circuit 4, the field memory 6, and the 
32.4-MHz interfield interpolation circuit 27 are similar to the 
corresponding component parts respectively in the aforementioned 
embodiments and therefore will not be described any further. Numeral 31 
designates a mixer for mixing the two-dimensionally interpolated present 
signal with the interframe-interpolated signal in accordance with the 
output of the motion detection circuit 11, and numeral 32 a mixer for 
mixing the output of the LPF circuit 4 with the output of the 32.4-MHz 
interfield interpolation circuit 27 in accordance with the output of the 
motion detection circuit 11. 
The operation of the embodiment 16 will be explained. First, the signal 
processed in the input processing section 1 is frame-delayed at the frame 
memory 2, and the signals before and after the delay are subjected to 
interframe interpolation at the interframe interpolation circuit 3. The 
signal input-processed in the input processing signal 1 is also 
two-dimensionally interpolated at the two-dimensional interpolation 
circuit 18. The interframe-interpolated signal is mixed with the 
two-dimensionally interpolated signal at the mixer 31 in accordance with 
the output of the motion detection circuit 11. The signal thus mixed is 
processed for moving and still images. For the still image, all the 
information reproducible between frames is reproduced without any 
aliasing. 
Next, the high-frequency component of 12-MHz or higher is removed from the 
output of the mixer 31 at the LPF circuit 4, the output of which is 
outputted to the field memory 6 and the 32.4-MHz interfield interpolation 
circuit 27. The resulting signal and the signal field-delayed at the field 
memory 6 are subjected to 32.4-MHz interfield interpolation at the 
32.4-MHz interfield interpolation circuit 27 as according to the 
embodiments 1-4. The signal thus interfield-interpolated is mixed with the 
output signal of the LPF circuit 4 in accordance with the output of the 
motion detection circuit 11. The mixing operation at the mixer 32 finishes 
all the MUSE processings including interfield processing of still images. 
As compared with the prior art, the embodiment under consideration saves 
the sampling frequency conversion circuit and subjects the 
interframe-interpolated signal mixed with the moving image signal to 
interfield interpolation. Therefore, the interfield interpolation circuit 
can be easily segmented facilitating an LSI configuration 
Embodiment 17: 
Now, an embodiment 17 (claim 19) will be explained. FIG. 31 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 17. In FIG. 31 (embodiment 17), the difference 
from FIG. 30 (embodiment 16) resides in that the interframe interpolation 
circuit 3 is removed, the frame-delayed signal is outputted through the 
two-dimensional interpolation circuit 18, the mixer 31 is replaced by a 
mixer 33 for mixing up to the average between the two-dimensionally 
interpolated present signal and the frame-delayed two-dimensionally 
interpolated signal from the two-dimensionally interpolated present 
signal, and the LPF circuit 4 is also removed. 
The operation of this embodiment will be explained. The present signal and 
the frame-delayed signal are two-dimensionally interpolated at the same 
two-dimensional interpolation circuits 18, 18, and the mixer 33 mixes from 
the two-dimensionally interpolated present signal up to the average 
between the two-dimensionally interpolated present, signal and the 
frame-delayed two-dimensionally interpolated signal. Then the average 
between the two-dimensionally interpolated present signal and the 
frame-delayed two-dimensionally interpolated signal is equivalent to the 
signal subjected to interframe interpolation and the two-dimensional 
filtering. As a result, the output of the mixer 33 becomes an output that 
has been interframe interpolated and two-dimensionally filtered. Also, by 
substituting the interframe interpolation circuit 3 for the 
two-dimensional interpolation circuit 18, the output thereof can be 
utilized also for the motion detection circuit 11 thereby to reduce the 
circuit size. 
The output of the mixer 33 is two-dimensionally filtered all the time. When 
the frequency characteristic of the two-dimensional interpolation circuit 
18 is rendered equivalent to the characteristic of the LPF circuit 4 or 
such as to cut off the frequencies of 12-MHz or higher, therefore, the LPF 
circuit 4 can be done without, thereby leading to a reduced circuit size. 
Embodiment 18: 
Now, an embodiment 18 (claim 20) will be explained. FIG. 32 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 18. In FIG. 32 (embodiment 18), the system is 
different from that of FIG. 30 (embodiment 16) in that an HPF circuit 34 
with a threshold frequency of 8.1-MHz is inserted between the LPF circuit 
4 and the 32.4-Hz interfield interpolation circuit 27, and the field 
memory 6 is replaced by a field memory 36 For delaying one field from 
8.1-MHz to 12.15-MHz. 
The operation of this embodiment will be explained. The signal subjected to 
interframe interpolation at the interframe interpolation circuit 3 is 
mixed at a mixer 31 with the signal subjected to two-dimensional 
interpolation at the two-dimensional interpolation circuit 18. In the 
signal with the components of 12-MHz or more removed at the LPF circuit 4, 
the components reproducible as high-frequency components at the 32.4-MHz 
interfield interpolation circuit 27 are those of 8.1-MHz or higher. It is 
therefore meaningless to input the components of 8.1-MHz or less to the 
32.4-MHz interfield interpolation circuit 27 and the field memory 36. Thus 
the HPF circuit 34 is inserted after the LPF circuit 4 to remove the 
components of 8.1-MHz or lower. In view of the fact that the components of 
8.1-MHz or lower have been removed at the HPF circuit 34, the band 
required for field delay is 8.1-MHz to 12.15-MHz. The required band is 
thus reduced to 1/3 as compared with the prior art. The use of the field 
memory 36 for delaying one field from 8.1 MHz to 12.15-MHz saves the 
memory capacity to one third of that of the conventional memories. 
A similar effect is obtained by using a field memory for field-delaying 
from 8.1-MHz to 16.2-MHz, in which case the memory capacity is reduced to 
one half. Further, the interframe interpolation circuit 3 which was used 
in the embodiment 17 may be removed, two-dimensional interpolation 
circuits 18, 18 are inserted for the interframe delay signal and the 
present signal respectively, and the LPF circuit 4 may be removed with an 
HPF circuit 34 newly inserted to make up a system having the same effect. 
Embodiment 19: 
Now, an embodiment 19 (claim 21) will be explained. FIG. 33 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 19. In FIG. 33 (embodiment 19), the difference 
from FIG. 30 (embodiment 16) lies in that the LPF circuit 4 is removed, a 
BPF circuit 35 for passing the band from 8.1-MHz to 12.15 MHz is inserted 
between the mixer 31 and the 32.4-MHz interfield interpolation circuit 27, 
and the field memory 6 is replaced by a field memory 36 for delaying one 
field from 8.1-MHz to 12.15-MHz. 
The operation of this embodiment will be explained. As described with 
reference to the embodiment 18, the components reproducible as 
high-frequency components at the 32.4-MHz interfield interpolation circuit 
27 are those from 8.1 MHz to 12.15-MHz. Once the components from 8.1-MHz 
to 12.15 MHz have been extracted by the BPF circuit 35, therefore, the 
field memory 36 can be used for delaying one field from 8.1-MHz to 
12.15-MHz thus saving the memory capacity to one third as compared with 
the prior art. 
Also, the same effect can be obtained by using a field memory for 
field-delaying from 8.1-MHz to 16.2-MHz, in which case the memory capacity 
saved is one half. Further, a system as shown in the embodiment 17 has a 
similar effect if a BPF circuit 35 is inserted therein for passing the 
band from 8.1-MHz to 12.15-MHz. 
Embodiment 20: 
Now, an embodiment 20 (claim 22) will be explained. FIG. 34 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 20. In FIG. 34, the input processing section 
1, the field memory 13, the interframe interpolation circuit 3, the 
two-dimensional interpolation circuit 18, the LPF circuit. 4, the 32.4-MHz 
interfield interpolation circuit 27, the delay circuit 29, the motion 
detection circuit 11 and the mixer 12 are similar to the corresponding 
component parts in the above-mentioned embodiments, and therefore will not 
be described again. The motion detection memory 20, however, has a smaller 
capacity than the memory 10. 
The operation of this embodiment will be explained. Three field memories 
13, 13, 13 in series operate in such a manner that a one-field delayed 
signal, a one-frame delayed signal and a one-field plus one-frame delayed 
signal are obtained from the signal processed at the input processing 
section 1. The interframe interpolation circuits 3, 3 perform interframe 
interpolation between the present signal anti the one-frame delayed signal 
one the one hand and between the one-field delayed signal and the 
one-field plus one-frame delayed signal on the other. These two 
interframe-interpolated signals, which are one field apart from each 
other, are passed through the LPF circuits 4, 4 thereby to remove the 
components of 12-MHz or higher, followed by interfield interpolation at 
the 32.4-MHz interfield interpolation circuit 27. 
In this configuration, the field memories 13 have a sampling frequency of 
only 16.2-MHz as for the present signal. Unlike in the conventional 
configurations requiring one-field delay at 32.4-MHz for 32.4-MHz 
interfield interpolation, therefore, the 4M-bit memory of the field memory 
6 is done without. 
Also, as shown in FIG. 34, all the outputs of the field memory 13 are 
inputted to the motion detection circuit 11, and the one-frame difference 
and the two-frame difference can be detected from these outputs for motion 
detection, thus permitting the field memory 13 to double as the 
above-mentioned motion detection memory 10. The motion detection memory 20 
according to the embodiment 20, therefore, is very compact as compared 
with the prior art and can thus reduce the memory capacity thereof. 
Embodiment 21: 
Now, an embodiment 21 (claim 23) will be explained. FIG. 35 is a block 
diagram showing the configuration of a high definition TV receiver 
according to the embodiment 21. In FIG. 35 (embodiment 21), the difference 
from FIG. 34 (embodiment 20) lies in that the interframe interpolation 
circuit 3 and the LPF circuit 4 are removed. Instead, two-dimensional 
interpolation circuits 18, 18, 18, 18 are connected at the output side of 
the three field memories 13 and the input processing section 1, together 
with two averaging circuits 37, 37 for averaging the outputs of the 
two-dimensional interpolation circuits 18, 18, 18, 18. The outputs of the 
averaging circuits 37, 37 are inputted to the 32.4-MHz interfield 
interpolation circuit 27. 
The operation of this embodiment will be described. As in the embodiment 
20, a one-field delayed signal, a one-frame delayed signal and a one-field 
plus one-frame delayed signal are produced. These signals and the present 
signal are two-dimensionally interpolated at the two-dimensional 
interpolation circuits 18, 18, 18, 18. The averaging circuits 37, 37 
determine the average between the two-dimensionally interpolated present 
signal and the one-frame delayed two-dimensionally interpolated signal, 
and the average between the one-field delayed two-dimensionally 
interpolated signal and the one-field plus one-frame delayed 
two-dimensionally interpolated signal. This averaging process is 
equivalent to two signals being interframe-interpolated and 
two-dimensionally filtered. Since these two signals are one field apart, 
they are subjected to interfield interpolation at the 32.4-MHz interfield 
interpolation circuit 27. 
When the two-dimensional interpolation circuits 18 are equivalent in 
characteristics to the LPF circuit 4 or have characteristics to cut off 
12-MHz or higher frequencies, the LPF circuit 4 is done without, thereby 
reducing the circuit dimensions. Also, in view of the fact that the field 
memory 13 described with reference to the embodiment 20 is operated with 
16.2-MHz, it can double as a motion detection memory. Thus a 
small-capacity memory 20 can be used for a reduced cost. 
Embodiment 22: 
Now, an embodiment 22 (claim 24) will be explained. FIG. 36 shows an 
embodiment using a frame memory, FIG. 37 the timing chart of the 
embodiment in FIG. 36, and FIG. 38 an embodiment using two field memories. 
In these diagrams, numeral 2 designates a frame memory, numeral 11 a 
motion detection circuit, and numeral 13 field memories. 
The operation of this embodiment will be explained. The frame memory 2 is a 
4-Mbit general-purpose memory of first-in first-out type for delaying by 
one frame the data of 16.2-MHz sampling frequency subjected to input 
processings. The effective video data of the MUSE signal is about 4 Mbits 
(3.86 Mbits) for the frequency of 16.2-MHz, and therefore a 4-Mbit memory 
can delay one frame. In case of a memory where a delay corresponding to 
reset intervals occurs when write and read resets are applied in the same 
way, for example, the one frame delay can be realized by setting the reset 
intervals to one frame depending on the particular memory. 
In such a case, assume that the read reset is delayed with respect to the 
write set by one clock upon transmission of 2 and by two clocks upon 
transmission of 4 or advanced by one clock upon transmission of 14 and by 
2 clocks upon transmission of 12 in accordance with the one half of an 
even-numbered signal of the horizontal motion vector signal transmitted. 
Then, the even number of horizontal motion vectors can be met by the 
motion detection and the interframe interpolation processings. In the 
timing chart of FIG. 37, the solid line indicates the case where the 
horizontal motion vector is 4 and the dashed line when the horizontal 
motion vector is zero. 
Instead of using the frame memory 2 as described above, the field memory 13 
may be employed to attain the same effect. In such a case, the field 
memories 13, 13 of 2M-bit fist-in first-out-type are connected in series 
with a subsequent-stage memory controlled in read reset. 
Apart from controlling a read reset against a write reset memory as 
described above, the inverse control may be employed with equal effect. In 
such a case, the control direction is required to be opposite to the 
preceding case. Also, the read or write reset may be replaced by read or 
write enable, respectively. 
Embodiment 23: 
Now, an embodiment 23 (claim 25) will be explained. FIGS. 39 and 40 show 
specific block diagrams showing the embodiment. In the diagrams, numeral 
18 designates a two-dimensional interpolation circuit, numeral 41 a D 
flip-flop activated at 32.4-MHz, numeral 42 a 2-1 selector for selecting 
one out of two signals, and numeral 43 a 3-1 selector for selecting one 
out of three signals. 
The operation of this embodiment will be explained. In FIG. 39, a 
frame-delayed signal controlled by memory in accordance with a horizontal 
motion vector is inputted to and two-dimensionally interpolated by the 
two-dimensional interpolation circuit 18. The two-dimensional 
interpolation circuit 18 calculates and transmits the subsample phase of 
the luminance signal in accordance with the horizontal motion vector on 
encoder side. The interpolation therefore can be interpolated intact 
according to the subsample phase. The signal thus two-dimensionally 
interpolated makes up a 32.4-MHz sample frequency, which is delayed by one 
clock at the D flip-flop 41, and the signals before and after the delay 
are inputted to the 2-1 selector 42. The 2-1 selector 42 selects the 
output of the D flip-flop 42 when the least significant bit of the 
horizontal motion vector is 1, i.e., when the horizontal motion vector is 
odd-numbered. When the horizontal motion vector is 1, for instance, memory 
control is not done but the 2-1 selector 42 selects the output of the D 
flip-flop 41. When the horizontal motion vector is 3, on the other hand, 
the memory control handles one clock, to which the 2-1 selector operates 
accordingly. In this way, the requirements of horizontal motion vector can 
be completely met. 
This is also the case with FIG. 40. When the horizontal motion vector is 0, 
the 3-1 selector 43 selects a center output (the output of the first-stage 
D flip-flop 41). When the horizontal motion vector transmitted is any one 
of odd numbers from 0 to 7, the 3-1 selector 43 selects an output through 
the two D flip-flops 41, 41; and when the horizontal motion vector is any 
one of numbers from 8 to 15, it selects the output of the two-dimensional 
interpolation circuit 18. Between the cases of FIGS. 39 and 40, memory 
control is different for horizontal motion vectors of 8 to 15. When the 
horizontal motion vector is 15, for instance, one clock is advanced in 
FIG. 39, while the clock count remains unchanged in case of FIG. 40. 
The horizontal motion vector requirement can thus be met by adding a memory 
control and simple circuits as shown in FIGS. 39 and 40. 
Embodiment 24: 
Now, an embodiment 24 (claim 26) will be explained. FIG. 41 is a specific 
block diagram showing the embodiment, and FIG. 42 the timing chart of the 
embodiment in FIG. 41. In FIG. 41, numeral 2 designates a frame memory, 
numeral 11 a motion detection circuit, and numeral 44 a 6-line memory. 
The operation of this embodiment will be explained. Normally, a first-in 
first-out memory produces an output as it is amenable to the delay up to 
several hundred clocks for the read control including read reset and read 
enable as against the write control including write reset and write 
enable, but not amenable to a greater delay in which case a new data is 
produced. In view of the need of a maximum delay of 6 lines for the 
vertical motion vector, the frame memory is connected in series with a 
line memory of at least 6 lines to accommodate the vertical motion vector. 
In FIG. 41, the frame memory 2 is assumed to be identical to the frame 
memory described with reference to the embodiment 22. First, assume that 
the vertical motion vector is 0. If the read reset is controlled six lines 
shorter than for write reset, the output of the frame memory 2 is a 
delayed signal six lines shorter than one frame. This signal is delayed by 
six lines at the 6-line memory 44 in series with the frame memory 2 
thereby to delay by one frame. Then, when the vertical motion vector is 2, 
the read reset is controlled six lines shorter than write reset. Since the 
delay of 6 lines occurs at the 6-line memory 44, the output of the 6-line 
memory 44 is a signal delayed by one frame and two lines thereby making it 
possible to meet the vertical motion requirement. FIG. 42 is a timing 
chart with the vertical motion vector at 2. The read reset is advanced by 
four lines from the write reset. The 6-line subsequent delay, however, 
delays the output of the line memory by one frame plus two lines. The 
dashed line for read reset represents the case where the vertical motion 
vector is zero. 
Although the foregoing description concerns the frame memory 2, a similar 
effect is obtained by using the field memory 13. Field memories of 2-Mbit 
first-in first-out type are used in series and the read reset of the 
memory in a subsequent stage is controlled. 
In the foregoing description, the read reset is controlled against the 
write reset. Instead, the write reset can be controlled against the read 
reset with equal effect. In such a case, the direction of control is 
reversed. The read and write reset can also be replaced by the read and 
write enable respectively with equal effect. 
The manner in which 6-line memories are connected in series as mentioned 
above is also applicable to the 22nd and embodiments 23 for meeting both 
the horizontal and vertical requirements. 
Embodiment 25: 
Now, an embodiment 25 (claim 27) will be explained. FIG. 43 is a specific 
block diagram showing this embodiment, and FIG. 44 the timing chart of the 
embodiment in FIG. 43. In FIG. 43, numeral 41 designates a D flip-flop 
operated at 32.4 MHz, numeral 46 a 4-1 selector for selecting one from 
four signals, numeral 47 a circuit for converting a 32.4-MHz data to 
8.1-MHz, and numeral 48 a frame memory for delaying one frame at 8.1-MHz. 
Now, the operation of this embodiment will be explained. In FIG. 43, the 
input data is subjected to such processings as two-dimensional 
interpolation into 32.4-MHz. This input, data is passed through D 
flip-flops 41, 41, 41 in three serial stages to delay by three clocks, and 
the output thereof is supplied to a 4-1 selector 46. The 4-1 selector 46 
outputs a signal selected by a control signal, which signal, through a 
converter circuit 47 for converting 32.4 MHz to 8.1-MHz, is supplied to 
the frame memory 48 for delaying one frame at 8.1-MHz. The converter 
circuit 47 may alternatively be a simple decimation circuit. 
In order to accommodate the horizontal motion vector according to the 
embodiment 25, the read reset and read enable are made variable against 
the write reset and write enable being the write control as in the 
embodiment 22 when the horizontal motion vector is a multiple of four, 
i.e., 0, 4, 8 or 12. FIG. 44 shows the case where the horizontal motion 
vector is four. 
In other cases, the 4-1 selector 46 is controlled in such a way that the 
8.1-MHz frequency has the same phase as the 32.4-MHz data irrespective of 
the presence or absence of the horizontal motion vector in the 32.4-MHz to 
8.1-MHz converter circuit 47. When the horizontal motion vector 3 is 3, 
for example, the 32.4-MHz data is delayed by three clocks behind the 
preceding frame, so that a series connection of three D flip-flops 41, 41, 
41 and appropriate output selection attains a uniform phase. In spite of 
this, the 4-1 selector 46 is required to be controlled by the use of a sum 
of products or the like in such a manner that the 32.4-MHz frequency has 
the same phase as the 8.1-MHz frequency in accordance with the horizontal 
motion vector sent for each frame. By controlling the 4-1 selector 46 and 
the 8.1-MHz frame memory concurrently, the horizontal motion vector can be 
accommodated. As regards the vertical motion vector, on the other hand, a 
line memory of at least six lines is connected with the frame memory 48 to 
control the frame memory 48 as in the embodiment 24. 
Embodiment 26: 
Now, an embodiment 26 (claim 28) will be explained. FIGS. 45 and 46 are 
block diagrams showing the configuration of an image reproduction 
apparatus according to the embodiment 26. In FIGS. 45 and 46, numeral 49 
designates a motion vector detection circuit, and numeral 50 a gate 
circuit. 
The operation of this embodiment will be explained. In the MUSE format, the 
motion vector signal is transmitted in terms of frame, while the motion 
vector for the field requires calculations on decoder side. For the 
horizontal motion vector, the interframe motion vector at 32.4-MHz is 
halved to meet the phase requirement of 24.3-MHz. When this requirement is 
to be met by 32.4-MHz interfield interpolation, the circuit is 
complicated, thereby reducing the advantage of a smaller circuit size for 
the 32.4-MHz interfield interpolation. In case of 32.4-MHz interfield 
interpolation, therefore, the interframe interpolation meets the motion 
vector requirement while the interfield interpolation fails to meet, such 
a requirement according to the system of the embodiment 26. 
FIG. 45 shows a system described with reference to the embodiments 1-4, in 
which the interfield interpolation alone fails to meet the motion vector 
requirement. A motion vector detection circuit 49 detects which of the 
horizontal or vertical motion vector is detected by the input processing 
section 1 or the absence of detection. In the case where a motion vector 
is detected, the output of the 32.4-MHz interfield interpolation circuit 
27 is blocked at the 2-1 selector 42. 
FIG. 46 shows a system in which the 32.4-MHz interfield interpolation is 
inhibited in the presence of a motion vector in the system shown in the 
embodiment 5. The motion vector detection circuit 49 detects the presence 
or absence of a motion vector. Upon detection of a motion vector, the 
control signal of an adaptive mixer circuit 14 is fixed by a gate circuit 
50 to the interframe interpolation side, thereby inhibiting the 32.4-MHz 
interfield interpolation. 
Embodiment 27: 
Now, an embodiment 27 (claim 29) will be explained. FIG. 47 is a block 
diagram showing a system according to the embodiment under consideration. 
In FIG. 47, numeral 131 designates an input signal processing circuit for 
performing such processings as de-emphasis or control signal detection for 
the MUSE signal inputted thereto, PLL synchronization for resampling or 
the two-dimensional interpolation of the resampled data. The input 
processing circuit 131 includes a vertical scanning line converter circuit 
132, a coefficient generator circuit 133, and a line period generator 
circuit 134 for giving the input-processed signal to a vertical scanning 
line converter unit 162 for changing the number of vertical scanning 
lines. The vertical scanning line converter unit 162 gives the output 
signal thereof to a time-axis converter circuit 135 for converting the 
MUSE signal to NTSC signal on time axis. This signal is further given to 
an image processing circuit 136 for performing image-processings including 
contour correction or a blanking signal addition. The digital signal given 
to a D/A converter 10 is converted to an analog signal. 
FIG. 48 is a block diagram showing a specific example of the vertical 
scanning line converter unit 162 according to this embodiment. This 
vertical scanning line converter unit 162 includes a line memory 137 for 
delaying the luminance signal or the color difference signal in MUSE 
signal by one line, a variable coefficient multiplier 138 for multiplying 
the signal by a variable coefficient in accordance with the coefficient 
supplied from a coefficient generator circuit 133, two coefficient 
generator ROMs inserted in the coefficient generator 133 for generating a 
coefficient in accordance with the line from the signal outputted by a 
line period generator circuit 134, and a timing signal generator circuit 
140 for generating a timing signal such as a synchronization signal from 
the MUSE signal and controlling the line period generator circuit 134. 
FIG. 49 is a diagram for explaining the manner in which the sampling points 
are converted by the vertical scanning liner converter 162 shown in FIG. 
48 as a model. The MUSE format signal has 1032 effective scanning lines. 
Considering the fact that this figure is three short of 1035 for the high 
definition TV signal for the convenience of transmission, the number of 
effective scanning lines for the NTSC format is 483. The percentage of the 
effective scanning lines is 92% and therefore the ratio of effective 
scanning lines 15:7 for either format. In other words, by converting the 
effective scanning lines for MUSE signal to 7/15, i.e., by preparing seven 
out of the 15 scanning lines of the MUSE signal, the number of 483 is 
obtained thereby making possible entire vertical reproduction on the NTSC 
monitor. 
The vertical scanning line converter unit 162 shown in FIG. 48 represents 
the simplest configuration for 7/15 conversion. The operation with this 
conversion will be explained. The signal representing 1035 lines subjected 
to signal processing such as de-emphasis and two-dimensional interpolation 
at the input signal processing circuit 131 is inputted to the vertical 
scanning line converter circuit 132. The signal representing the 
initiation of the line to be converted at the timing signal generator 
circuit or the start of the video signal is inputted to the line period 
generator circuit 134. The line period generator circuit 134 outputs the 
signal associated with 1 to 15 at 15-line intervals iteratively to the 
coefficient generator circuit 133. A coefficient generator ROM 139 outputs 
coefficients of 1/7 to 1 (including 0) to the variable coefficient 
generator 138, in which the coefficient input-processed appropriately is 
multiplied by the same signal delayed by one line at the line memory 137. 
In this case, the two variable coefficient generators 138 are identical to 
each other, although the coefficient to be multiplied is different as 
shown in FIG. 49 and the sum of the two coefficients is designed to be 1. 
As a result, the scanning lines are converted from 15 to 7 at the vertical 
scanning line converter circuit 132. 
FIG. 50 is a block diagram showing another example of the vertical scanning 
line converter unit 162. The coefficient generator circuit 133 shown in 
FIG. 48 includes two coefficient generator ROMs 139. The coefficient 
generator circuit 133 shown in FIG. 50, however, includes a coefficient 
generator ROM 139 and an arithmetic circuit 190. Further, the input signal 
passed through the two line memories 37 and the fixed coefficient 
generator 191 are added together at the adder 119. In this way, the filter 
characteristic for generating seven out of 15 lines is improved using 
three linear interpolations. FIG. 51 shows the manner in which the 
sampling points are converted by the vertical scanning line converter unit 
162 shown in FIG. 50 as a model. As shown in FIG. 51, the coefficient is 
changed from 1/28 to 13/28. Basically, however, the principle remains 
unchanged as the coefficient changes at intervals of 15 lines. In this 
way, the signal subjected to scanning line conversion is converted in time 
axis at the time-axis converter circuit 135, image-processed at the image 
processing circuit 136 and converted into an analog signal at the D/A 
converter 110, thereby attaining the reproduction with total conversion 
along vertical direction on the NTSC monitor. 
The foregoing description concerns the full mode and the zoom mode for 
converting the scanning lines to 483. In spite of this, a similar 
conversion is possible in also the wide mode. The wide mode is for 
converting to the scanning lines 3/4of that for the full or zoom mode in 
order to maintain the roundness. Therefore, the 7/20 conversion by 
multiplying 7/15 by 3/4 is made or the conversion to 7/15 is followed by 
conversion to 3/4. More specifically, in order to generate seven out of 20 
scanning lines, the line period generator circuit 134 generates a signal 
representing one to 20 lines at intervals of 20 lines, and the resulting 
signal is outputted to the coefficient generator circuit for generating 
controlling coefficients of 1/7 to 1 (including 0). The wide mode thus can 
be attained. On the other hand, the same result is obtained by converting 
from 15 to seven lines by the aforementioned scanning line conversion 
followed by generating three out of four scanning lines. 
The variable coefficient generator in this embodiment is realized by the 
use of a multiplier or a ROM and an arithmetic circuit. Once ROMs for 
1/15, 2/15 and 3/15 conversion are prepared, for example, the rest is to 
multiply a coefficient simply by additions and subtractions. Although this 
embodiment includes a very simple vertical scanning line converter 
circuit, the aliasing distortion due to scanning line conversion can be 
reduced when the linear interpolation between a greater number of lines is 
used. Apart from the two-dimensional interpolation effected at the input 
signal processing circuit 131 shown in the embodiment under consideration, 
the vertical scanning line converter circuit 132 may also perform the 
two-dimensional interpolation at the same time, in which case the line 
memory can be reduced in capacity. 
Embodiment 28: 
Now, an embodiment 28 (claim 31) will be explained. The system blocks, 
which are similar to those for the embodiment 27 shown in FIG. 27, will 
not be described any further, but the explanation will be limited to the 
vertical scanning line converter for the luminance signal (Y signal). FIG. 
52 is a block diagram showing the simplest Y vertical scanning line 
converter according to the invention. In FIG. 52, numeral 141 designates a 
Y line memory for delaying the Y component of the MUSE signal by one line, 
numeral 142 a variable coefficient generator involving a fraction of power 
of two, and numeral 143 a line period generator circuit for generating an 
odd-numbered line period twice higher than that after conversion. 
Now, the operation will be explained. FIG. 53 is a diagram for explaining 
the manner of conversion using a model of sampling points. As explained 
with reference to the embodiment 27, when the MUSE signal effective 
scanning lines are reduced to 7/15, all the scanning lines can be 
converted to those for NTSC format in vertical scanning line conversion in 
full or zoom mode. In such a case, however, the linear interpolation 
coefficient between lines is complicated, and the circuit configuration 
requires a plurality of multipliers and ROMs. When the value of the 
numerator of the ratio 7/15 representing the relation for vertical 
scanning line conversion is approximated in the form of powers of two, the 
circuit can only comprise the fraction-of-power-of-two variable 
coefficient generator 142. When the ratio 7/15 is approximated by 4/9, for 
instance, the interline linear interpolation coefficients are sufficiently 
of five classes including 0, 1/4, 1/2, 3/4 and 1, which can be realized by 
bit shift, an adder and a simple gate circuit. The circuit size can thus 
be considerably saved. The coefficient 4/9 leads to 460 (=1035.times.4/9) 
scanning lines after conversion, which, though meets the effective NTSC 
scanning lines, has a considerable error of 23 lines. Actually, therefore, 
the use of 8/17 or 32/69 reduces the error to about four lines. Since both 
the ratios 8/17 and 32/69 are selected to make the numerator a power of 
two, the interline coefficients can thus be obtained with bit shift, an 
adder and a simple gate circuit. As described above, in vertical scanning 
line conversion in full or zoom mode, the numerator may assume a power of 
two and the denominator an odd number larger than twice the numerator for 
approximation. 
Also in wide mode, as described with reference to the embodiment 27, the 
vertical scanning lines are converted to 7/20. As in full and zoom modes, 
this particular ratio complicate coefficients for interline linear 
interpolation. Therefore, approximation of 7/20 by another fraction having 
a numerator equal to a power of 2 and a denominator of an odd number twice 
larger than the numerator simplifies the circuit considerably as in the 
previously described cases. If 7/20 is approximated by such ratio as 4/11 
or 8/23, for instance, the interline linear interpolation coefficients can 
be realized with bit shift, an adder and a simple gate circuit. 
This fact will be explained with reference to FIGS. 52 and 53. For 
simplicity, assume that when the simplest ratio of 4/9 is employed for 
vertical scanning line conversion in full or zoom mode, the circuit 143 
for generating a line period of an odd number twice larger than the 
converted lines generates signals 1 to 9 for a 9-line period. Five classes 
of coefficients 0, 1/4, 1/2, 3/4 and 1 are generated by the coefficient 
generator 133, the lines are multiplied by a coefficient at the 
fraction-of-power-of-two variable coefficient multiplier 142, and linear 
interpolation is effected between lines. Since the linear interpolation 
between two lines is at 9 line intervals and a very simple coefficient is 
involved, as shown in FIG. 53, the variable coefficient multiplier 142 
involving a fraction of power of 2 can be constructed of a very simple 
configuration. Also, the ratio 8/17 for full and zoom mode and 8/23 for 
wide mode represent a 17-line period and a 23-line period respectively 
with the interline linear interpolation coefficients in the range of 1/8 
to 1 (including 0), which can be realized simply with one more bit shift 
and one more arithmetic circuit. 
FIG. 54 is a diagram showing another application of the embodiment under 
consideration. In this application, the ratio for vertical scanning line 
conversion remains the same and the interline linear interpolation 
involves three lines to improve the filter characteristics. More 
specifically, in addition to the configuration of FIG. 52, the system 
further comprises another Y line memory 141 and a another 
fraction-of-power-of-two variable coefficient multiplier 142. The signals 
passed through the two Y line memories 141 and two fraction-power-of-two 
variable coefficient multipliers 142 are also given to the adder 119 and 
the each other. The circuit operation, which is identical to that in FIG. 
52, is such that vertical scanning line conversion to 4/9 produces four 
lines per nine lines whereas 3-line linear interpolation somewhat 
complicates the coefficients. The linear interpolation using many lines as 
in this case complicates the coefficients, although the filter 
characteristic can be improved and the aliasing distortion due to the 
vertical scanning line conversion is reduced. Although the example under 
consideration concerns the vertical scanning line conversion, when 
horizontal arithmetic operation is added in subsample phase of the 
luminance signal in the process of interline linear interpolation, then 
the arithmetic operation for two-dimensional interpolation can be effected 
at the same time thereby to conserve the capacity of the line memories. 
Embodiment 29: 
Now, an embodiment 29 (claim 32) will be explained. FIG. 55 is a block 
diagram showing a vertical scanning line converter unit 162 for the color 
difference signal according to this embodiment. In FIG. 55, numeral 144 
designates a color difference line memory for delaying the color 
difference signal by one line, numeral 145 a 1/2-fraction variable 
coefficient multiplier for Y scanning line conversion specified for the 
system, and numeral 146 a circuit for generating a line period twice of 
that for Y signal specified for the system. 
FIG. 56 is a diagram for explaining the circuit operation of the block 
shown in FIG. 55 by a model of sampling points. The conventional color 
difference signal is filtered to a vertical phase adjusted at a point 
where 516 scanning lines for luminance signal is involved, i.e., each 
scanning line is generated from each two scanning lines in full or zoom 
mode. In the absence of vertical scanning line conversion, only a vertical 
filter is used. In wide mode, on the other hand, the 516 vertical scanning 
lines are reduced to 2/3 for both the color difference signal and the 
luminance signal. As shown in the embodiments 27 and 28, however, 
conversion of the effective scanning lines of luminance signal from 1032 
to 483 in full or zoom mode requires conversion of the vertical scanning 
lines also for color difference signal from 516 to 483. In wide mode, 
therefore, the vertical scanning lines for the color difference signal 
must be converted directly to 7/20 i.e., from 1032 to about 360. The color 
difference signal in MUSE signal is transmitted every other line with one 
half of the number of scanning lines of luminance signal. Converting the 
MUSE color difference signal with the same line period as the luminance 
signal is difficult with such coefficients as 7/15 or 4/9 for the 
embodiment 27 and 28 since the line period is odd numbered. A solution is 
to convert the scanning lines to twice with the line period twice of that 
of the luminance signal. When the ratio is 7/15 for the luminance signal, 
for example, the ratio of 28/30 is used for the color difference signal. 
In similar fashion, in the case of 4/9 or 8/17 for the luminance signal, 
the ratio of 16/18 or 32/34 respectively is employed for conversion of the 
color difference signal. The denominator of these coefficients represents 
the scanning lines of the MUSE signal and includes the two color 
difference signals, while the numerator is the sum of the scanning lines 
for the two color difference signals after conversion. As a result, from 
the viewpoint of only one of the color difference signals, both the 
denominator and numerator become one half, so that the above-mentioned 
conversion employs 14/15, 8/9 and 16/17, and the interline linear 
interpolation coefficients are one half of that for the luminance signal. 
The ratio 1/7, for instance, changes to 1/14, and 1/4 to 1/8. This is also 
the case with wide mode, in which case an assumed ratio of 7/20 for 
luminance signal is associated with the ratio of 14/20 for one color 
difference signal and 28/40 for the two color difference signals. 
Assume that the luminance signal conversion is 4/9 in the explanation made 
above with reference to the embodiment 28 in full or zoom mode, for 
example. Then the vertical scanning line conversion for the color 
difference signal is performed in the following manner. The circuit 146 
for generating a line period twice of that of the luminance signal 
generates 18 lines of line period. The coefficient generator circuit 133 
generates a coefficient, the variable coefficient multiplier 145 involving 
the fraction of 1/2 of that for the luminance signal multiplies the 
coefficient, and linear interpolation is performed between two lines which 
are apart by two lines from each other. In FIG. 56, the black circle 
represents an R luminance signal, and the hatched circle a B luminance 
signal. The vertical position of the color difference signal after 
conversion is designed to correspond to that of the luminance signal. As 
seen from the diagram, the coefficient for the color difference signal is 
one half of that for interline linear interpolation for the luminance 
signal, i.e., 1/8 to 1 (including 0). Further, the conventional vertical 
filter for the color difference signal has a fixed coefficient. In order 
to adjust the vertical positions of the two color difference signals and 
the luminance signal, therefore, the color difference signals required 
different filters. In case of the vertical scanning line converter circuit 
under consideration, however, a single circuit serves the purpose since 
the two color difference signals are processed in time series. 
FIG. 55 is a block diagram showing a simplest, specific example of this 
embodiment. The use of a greater number of line memories for the color 
difference signal can reduce the aliasing distortion due to the vertical 
scanning line conversion. Also, by performing the arithmetic operation for 
horizontal direction in accordance with the subsample phase of the color 
difference signal at the time of linear interpolation in the vertical 
scanning line converter circuit, the circuit can double as a 
two-dimensional interpolation circuit for the color difference signal, 
thereby reducing the size of the circuit and the required capacity of the 
line memory. 
Embodiment 30: 
Now, an embodiment 30 (claim 33) will be explained. FIG. 57 is a block 
diagram showing the configuration of a vertical scanning line converter 
circuit 162 according to this embodiment. This vertical scanning line 
converter circuit 162 includes a line memory 137, two variable coefficient 
multipliers 138, an adder 119 for adding the input signal passing through 
the line memory 137 and the variable coefficient multiplier 138 to the 
input signal passing only through the variable coefficient multiplier 138, 
a timing signal generator circuit 140, a first coefficient generator 
circuit 147, a first line period generator circuit 148, a second 
coefficient generator circuit 149, a second line period generator circuit 
150, and a switch 151 for switching the mode of vertical scanning line 
conversion. 
The operation of this embodiment will be explained. FIG. 58 is a diagram 
for explaining the operation of the vertical scanning line converter unit 
162 with a model of sampling points. In the conventional M-N converter, a 
vertical scanning line converter circuit is required for each of full, 
zoom and wide modes. As a result, a plurality of line memories and 
arithmetic circuits are required thereby leading to the disadvantage of a 
large circuit size. According to this embodiment, by contrast, this 
problem is solved and the effective MUSE scanning lines after conversion 
can be converted entirely into those for the NTSC format. As described 
above with reference to the embodiment 27, the conversion of the MUSE 
vertical scanning lines to 7/15 permits conversion to within the 483 
effective scanning lines for NTSC format in full or zoom mode. In similar 
manner, from the viewpoint of maintaining the roundness, the vertical 
scanning lines for the MUSE signal are converted to 7/20 in wide mode. In 
this case, the coefficient 7/15 for conversion of the vertical scanning 
lines in full or zoom mode and the coefficient 7/20 for the vertical 
scanning line conversion in wide mode are in the ratio ranging from 1/7 to 
1 (including 0) in case of linear interpolation between two lines. If the 
line period is changed to 15 and 20 lines with different coefficients 
generated for each line, then a vertical scanning line converter circuit 
can be shared without substantial change. 
FIG. 57 is a diagram showing a simplest specific example. The timing signal 
generator circuit 140 generates a conversion start signal for MUSE signal, 
which signal is received to the first line period generator circuit 148, 
which in turn outputs 1 to 15 to the first coefficient generator circuit 
147 at intervals of 15 lines, for example. In similar fashion, the second 
line period generator circuit 150 outputs 1 to 20 to the second 
coefficient generator circuit 149 at intervals of 20 lines, for example. 
The first and second coefficient generator circuits 147, 149 generate 
coefficients as shown in FIG. 58. For instance, the first coefficient 
generator circuit 147 generates 5/7 at the fourth line of the line period 
and 2/7 for a one-line delayed signal, while the second coefficient 
generator circuit 149 outputs 3/7 at the fifth line and 4/7 for a one-line 
delayed output signal. In this way, the coefficients are a fraction from 1 
to 1/7. Since the line period and generation of coefficients are in 
different sequences, 2-1 selectors S.sub.1, S.sub.2 are controlled by the 
mode change-over switch 151 to accommodate a mode change. As seen from 
above, the line memory 137, the variable coefficient multiplier 138 and 
the adder can be integrated into a single unit, so that the circuit and 
the line memory can be reduced in size. 
Although the foregoing description concerns the switching between full, 
zoom and wide modes, a mode requiring vertical scanning line conversion to 
maintain the roundness can also be met by changing the line period and the 
coefficient generator circuit. In such a case, the sharing of a variable 
coefficient multiplier by different circuits is also possible although the 
variable coefficient multiplier may be somewhat different depending on the 
coefficient. In spite of the linear interpolation between two lines 
described above according to this embodiment, the aliasing distortion due 
to the vertical scanning line conversion can be reduced by using a greater 
number of line memories. Also, when the arithmetic operation in horizontal 
direction is performed in accordance with the subsample phase at the time 
of linear interpolation in the vertical scanning line converter circuit, 
then the particular operation can be performed also by the two-dimensional 
interpolation circuit for a reduced circuit size and line memory capacity. 
Embodiment 31: 
Now, an embodiment 31 (claim 34) will be explained. FIG. 59 is a block 
diagram showing a simplest vertical scanning line converter circuit 162 
according to the embodiment. In this embodiment, the system comprises a 
line memory 155 capable of delaying the MUSE signal by one line, a 
variable coefficient multiplier 138, a Y coefficient generator circuit 
152, a color difference signal coefficient generator circuit 153, a color 
difference signal line period generator circuit 154, and a timing signal 
generator circuit 140. 
The operation of this embodiment will be explained. FIG. 60 is a diagram 
for explaining the operation of the vertical scanning line converter unit 
162 shown in FIG. 59 as a model of sampling points. In the prior art, the 
color difference signal is not converted in the vertical scanning lines 
but filtered in accordance with the vertical position of the scanning 
line-converted luminance signal and therefore is processed by a circuit 
different from the luminance signal scanning line converter circuit. In 
wide mode, however, according to the prior art, the color difference 
signal is also subjected to vertical scanning line conversion, but only 
after temporal expansion. As a consequence, the luminance signal and the 
color difference signal are converted by different circuits hence leading 
to a larger circuit configuration. By taking advantage of the fact that 
the coefficient of 1/2 is used for the line period twice of that for Y 
shown in the 29th embodiment 29 and the horizontal luminance signal and 
the color difference signal for the MUSE signal are multiplexed on the 
time axis in time series, the coefficients for the signal line delay and 
the interline linear interpolation are rendered variable. Then, a single 
vertical scanning line converter circuit can be used for scanning line 
conversion of both the luminance signal and the color difference signal. 
In this way, the whole circuit including the line memory can be reduced in 
size as compared with the conventional system. The timing signal generator 
circuit 140 shown in FIG. 59 outputs a signal for switching the luminance 
signal and the color difference signal. When this signal represents the 
luminance signal, the delay is one line; while when this signal indicates 
the color difference signal, the delay is two lines. Also, the coefficient 
for interline linear interpolation is switched in the manner shown in FIG. 
60. As described with reference to the embodiment 29, when the color 
difference signal line period is twice as long as that of the luminance 
signal and the interline linear interpolation coefficient for the color 
difference signal is one half of that for the luminance signal, then a 
variable coefficient multiplier circuit 138 capable of meeting the color 
difference signal coefficient can be used also for the luminance signal. 
Assume, for example, that as shown in FIG. 60 the luminance signal is 
converted to 4/9 in vertical scanning lines in full or zoom mode. The 
ratio for the two color difference signals is 16/18. This indicates that 
the scanning line conversion at 18-line intervals attains 8-line 
conversion for both the luminance signal and the color difference signal. 
The minimum coefficient for linear interpolation is 1/8 for the color 
difference signal, which can be used also by the luminance signal as 1/4. 
Thus the variable coefficient multiplier 138 can be shared with equal 
effect. 
According to this embodiment, the linear interpolation between two lines is 
treated. When a greater number of line memories are used, however, the 
aliasing distortion due to the vertical scanning line conversion can be 
reduced. Also, a simultaneous arithmetic operation in horizontal direction 
in accordance with the subsample phase at the time of linear interpolation 
in the vertical scanning line converter circuit can reduce the circuit 
size and the line memory capacity, since this function doubles as a 
two-dimensional interpolation circuit. 
Embodiment 32: 
Now, an embodiment 32 (claim 35) will be explained. FIG. 61 is a block 
diagram showing the configuration of a simplest vertical scanning line 
converter circuit 162 according to this embodiment. This embodiment 
comprises a line memory 155 capable of delaying the MUSE signal by one 
line, a color difference signal line memory 144, a first line period 
generator circuit with a coefficient generating function 156, a second 
line period generator circuit with a coefficient generating function 157, 
a variable coefficient generator 142 involving a fraction of a power of 
two, a Y coefficient generator circuit 152, a color difference signal 
coefficient generator circuit 153, a color difference signal line period 
generator circuit 154, a timing signal generator circuit 140, and a mode 
change-over switch 151. 
The operation of this embodiment will be explained. As described with 
reference to the embodiments 30 and 31, a vertical scanning line converter 
circuit is used for a plurality of modes also according to the embodiment 
under consideration. Assume that the first, or second line period 
generator with a coefficient generating function is switched depending on 
the mode and the vertical scanning line converter is switched by changing 
the coefficients for the luminance signal and the color difference signal 
in horizontal direction to share the same vertical scanning line converter 
circuit. When all the conversion coefficients are a fraction of a power of 
two, the coefficient multipliers can be configured of an adder and a 
simple gate circuit with bit shift. In this way, the circuit is reduced 
considerably in size. Assume in full or zoom mode that the luminance 
signal is converted to 8/17 and the color difference signal to 32/34 with 
the first line period generator circuit with a coefficient generating 
function 156 selected in FIG. 61. Then the line period covers 34 lines 
with the coefficient, at a minimum of 1/16. When the conversion in wide 
mode involves the second line period generator with a coefficient 
generating function 157 with the luminance signal converted to 8/23 and 
the color difference signal to 32/46, the minimum coefficient is 1/16. 
More specifically, a variable coefficient multiplier for 1/16 to 1 can be 
shared by the luminance signal and the color difference signal in full, 
zoom and wide modes. The 1/16-1 variable coefficient multiplier can be 
realized with a maximum of four-bit shift, a simple gate circuit and an 
adder, and eliminates the need of a ROM or a multiplier, thus considerably 
reducing the circuit size. 
Apart from the linear interpolation between two lines according to the 
embodiment under consideration, the aliasing distortion due to the 
vertical scanning line conversion can be reduced using more line memories. 
If the arithmetic operation for the horizontal direction is performed in 
accordance with the subsample phase at the time of linear interpolation in 
the vertical scanning line conversion, on the other hand, the circuit can 
be shared by two-dimensional interpolation, thus contributing to a reduced 
size of the circuit and the line memory. 
Embodiment 33: 
Now, an embodiment 33 (claim 36) will be explained. FIG. 62 is a block 
diagram showing the configuration of a simplest vertical scanning line 
converter unit 162 according to this embodiment. The embodiment under 
consideration comprises a line memory 155 for delaying the MUSE signal by 
one line, a first field coefficient generator circuit 158, a second field 
coefficient generator circuit 159, a variable coefficient multiplier 138, 
a line period generator circuit 160, and a timing signal generator circuit 
140. 
The operation of this embodiment will be explained. FIG. 63 is a diagram 
for explaining the operation of the vertical scanning line converter unit 
162 shown in FIG. 62 as a model of sampling points. In the conventional 
M-N converter, in order to adjust the interlace between fields strictly, 
an additional vertical scanning line converter circuit is used or an error 
is tolerated to some degree. According to this embodiment, by contrast, 
the interfield interlace is secured easily by the use of the vertical 
scanning line converter circuit according to the foregoing embodiments. 
For this purpose, as shown in FIG. 62, a field decision signal of the 
output of the timing signal generator circuit 140 is used to switch the 
outputs of the first field coefficient generator circuit 158 and the 
second field coefficient generator circuit 159, with the resulting signal 
multiplied by a coefficient at the variable coefficient multiplier 138 for 
linear interpolation. In the process, a coefficient one half of that for 
the original conversion is used, and the numerator of the coefficient 
generated at the first field coefficient generator circuit 158 is assumed 
to be an even number, while that of the second field coefficient generator 
circuit 159 an odd number. Then the interlace can easily be maintained. As 
shown in FIG. 63, for example, the coefficient 1/8 is used instead of 1/4 
as a minimum for the 4/9 vertical scanning line conversion in full or zoom 
mode. Also a coefficient equivalent to an even number, i.e., a multiple of 
one fourth is used as the numerator for the first field, and the 
coefficient 1/8 for the second field in order to maintain the interlace. 
Embodiment 34: 
Now, an embodiment 34 (claim 37) will be explained. FIG. 64 is a block 
diagram showing the configuration of an M-N converter according to this 
embodiment corresponding to FIG. 47. This embodiment comprises a signal 
multiplexer circuit 170 interposed between the vertical scanning line 
converter unit 162 and the time-axis processing circuit 135 shown in the 
embodiments 27-33. The signal multiplexer circuit 170 includes two color 
difference signal line memories 144, a control signal generator circuit 
164 for controlling the delay of the color difference signal from the 
output of the line period generator circuit 134 in the vertical scanning 
line converter unit 162, a 3-1 selector 165 for selecting one of three 
signals, and a time-axis conversion memory 163. The input side terminal of 
the 3-1 selector 165 is supplied with the output signal of the vertical 
scanning line converter unit 162, the output signal of the vertical 
scanning line converter unit 162 through one color difference signal line 
memory 144 and the output signal of the vertical scanning line converter 
unit, 162 through two color difference signal line memories 144. The 2-1 
selector S.sub.11 for selecting the signal supplied from the output side 
terminal of the 3-1 selector 165 and the output signal of the vertical 
scanning line converter unit 162 is controlled by the control signal 
generator circuit 164. 
The operation of this embodiment will be explained. FIG. 65 is a timing 
chart for explaining this embodiment. In the conventional M-N converter, 
two memories for time-axis conversion, including one for odd-numbered 
lines and the other for even-numbered lines, and three conversion memories 
for vertical compression in wide mode are required. According to the 
embodiment under consideration, in order to obviate this problem, the 
color difference signal of the output of the vertical scanning line 
converter unit 162 described in the embodiments 27-33 is delayed by two 
lines at maximum so that the luminance signal and the color difference 
signal are rearranged in such an order as to provide a single time-axis 
conversion memory and a single vertical compression memory. The circuit 
size is thus reduced to a degree suitable for LSI configuration. As shown 
in the block diagram of FIG. 64, the color difference signal output from 
the vertical scanning line converter unit 162 shown in the embodiments 
27-33 is delayed by two lines at the color difference signal line memory 
144, and the three signals before and after the delay are connected to the 
3-1 selector 165. The output of the vertical scanning line converter unit 
162, as shown in the top stage of FIG. 65, for example, has the luminance 
signal and the color difference signal not arranged in order. This is 
because the conversion process uses the linear interpolation with the 
conversion rate of 7/15 or 7/20, and therefore the conversion is not 
applied to all the lines. As a result, the color difference signal leads 
by two lines at maximum, and the output sequence of the color difference 
signal is changed. In view of this, the color difference signal is delayed 
by the line memory 144, and the output of the line period generator 
circuit 134 of the vertical scanning line converter unit 162 is supplied 
to the control signal generator circuit 164. The delay of the two color 
difference signals is controlled by the 3-1 selector 165 respectively 
through the control signal generator circuit 164 and thus they are 
rearranged as shown in the timing chart shown in the middle of FIG. 65. In 
this way, the data can be written in the time-axis conversion memory 163 
in good order. The hatched portions of the timing chart represent invalid 
data and therefore are not written in. By writing the luminance signal and 
the color difference signal in good order into the time-axis conversion 
memory 163, the memories can be used efficiently and can double as the 
time-compression memory in wide mode. Since the reading operation on the 
read side of the time-axis conversion memory 163 is performed in order, 
the circuit can be reduced in size. 
Although the delay of the color difference signal is assumed to be two 
lines at maximum, the delay of at least two lines is required depending on 
the trade-off between the four-line advance and the delay of the color 
difference signal of MUSE format. Also, the time-axis conversion memory 
163 can be written into with a timing chart as shown in the bottom of FIG. 
65, in which case the circuit configuration after time-axis conversion is 
simplified. 
Embodiment 35: 
Now, an embodiment 35 (claim 38) will be explained. FIG. 66 is a block 
diagram showing the configuration of an M-N converter according to this 
embodiment. This embodiment comprises a signal multiplexer circuit 170 
having a configuration different from the embodiment 34 inserted between 
the vertical scanning line converter unit 162 and the time-axis processing 
circuit 135 shown in the embodiments 27-33. The signal multiplexer circuit 
170 includes two color difference signal line memories 144, a color 
difference signal expansion circuit 166 for expanding the time axis of the 
color difference signal, a control signal generator circuit 164 for 
controlling the delay of the color difference signal in accordance with 
the output of the line period generator circuit 134 in the vertical 
scanning line converter unit 162, a horizontal timing control circuit 167, 
3-1 selectors 165, 165 each for selecting one of three signals, a memory 
168 for multiplexing the luminance signal, a memory 169 for multiplexing 
the color difference signal, and a time-axis conversion memory 163. The 
input side terminals of the 3-1 selectors 165, 165 are supplied with an 
output signal of the vertical scanning line converter unit 162 through the 
color difference signal expansion circuit 166, an output signal of the 
vertical scanning converter 162 through one of the two line color 
difference signal memories 144, and an output signal of the vertical 
scanning line converter unit 162 through the two color difference signal 
line memories 144. The 2-1 selector S.sub.14 for selecting the signal 
given from the output side terminals of the 3-1 selectors 165, 165 is 
controlled by the horizontal timing control circuit 167. The output side 
terminal of the 2-1 selector S.sub.16 is connected to the memory 169, and 
the vertical scanning line converter unit 162 to the memory 168. The 
memories 168, 169 are connected to the input side terminal of the selector 
S.sub.12, and the output side terminal of the 2-1 selector S.sub.12 to the 
time-axis conversion memory 163. The 2-1 selector S.sub.12 for selecting 
one of the memories 168 and 169 is controlled by the horizontal timing 
control circuit 167. 
Now, the operation will be explained. FIG. 67 is a timing chart for 
explaining the operation. The color difference signal of the MUSE signal 
is multiplexed on time axis and specifically transmitted by being 
compressed to 1/4 before the luminance signal. Therefore, the color 
difference signal is required to be expanded to four times after being 
received at the M-N converter. The conventional M-N converter in which the 
color difference signal is expanded by a fact, or of four for each color 
difference separately requires two time-axis expansion memories. The 
conventional M-N converter, as described above with reference to the 
embodiment 34 (claim 37), also requires two memories, one for time-axis 
conversion and the other for time-axis compression. According to the 
present embodiment, in order to obviate this problem, the color difference 
signal from the vertical scanning line converter unit 162 shown in the 
embodiments 27-33 is directly expanded, and therefore only one memory is 
required for the color difference signal expansion circuit. According to 
this embodiment, after adjusting the lines between the luminance signal 
and the color difference signal using two color difference signal line 
memories 144, the luminance signal and the color difference signals are 
expanded to 3/2 at the multiplexing memories 168, 169. After time-division 
multiplexing two luminance signals for each one color difference signal 
sequentially by the 2-1 selector, the multiplexed signal is taken to the 
time-axis conversion memory 68. As a result, the time-division 
multiplexing operation according to this embodiment is considered to 
simplify the subsequent circuits after time-axis conversion as it performs 
a part of the memory function for time-axis compression. 
First, in the output signal of the vertical scanning line converter unit 
162 shown in the embodiments 27-33, the color difference signal and the 
luminance signal are not matched in the number of lines, as shown in the 
timing chart at the top of FIG. 67. Only the color difference signal is 
first expanded by being written into an expansion memory. The expanded 
color difference signal is delayed by two lines at the line memory 144. 
The signals before and after this delay are switched to the same timing in 
accordance with the output signal of the control signal generator circuit 
164 at the 3-1 selector 165, after which the color difference signals are 
time-division multiplexed by the output signal of the horizontal timing 
control circuit 167. The multiplexed color difference signal and the 
luminance signal, as shown in the middle portion of FIG. 67, are such that 
the B-Y and the R-luminance signals are arranged alternately at time 
intervals corresponding to the period of 32.4-MHz for the luminance signal 
and 16.2-MHz for the color difference signal, or one half of the luminance 
signal. The luminance signal and the color difference signal are expanded 
to 3/2 at the multiplexing memories 168, 169, and the resulting expanded 
signal is switched at the 2-1 selector S.sub.12 for time-division 
multiplexing the luminance signal and the color difference signal. Then 
the timing chart shown at the bottom of FIG. 67 is obtained, so that two 
luminance signals are multiplexed with one color difference signal, other 
two luminance signals with another color difference signal, and so on. One 
cycle involves four luminance signals and one each of the difference 
signals as seen from the diagram. The color difference signal is expanded 
by a factor of four and registers with Y video signal in position. It is 
therefore possible to decode a multiplexed signal simply by extraction 
with a very simple circuit or easily by taking a timing after time-axis 
conversion. In the process, the color difference signal expansion is 
already complete, and therefore the circuit configuration can be 
simplified after time-axis conversion. 
Embodiment 36: 
Now, an embodiment 36 (claim 39) will be explained. FIG. 68 is a block 
diagram showing the configuration of an M-N converter according to this 
embodiment. The system according to this configuration comprises an input 
signal processing circuit 131, a vertical scanning line converter unit 162 
shown in the embodiments 27-33, a signal multiplexer circuit 170 shown in 
the embodiments 34 and 35, a time-axis conversion memory 163, a processing 
circuit after time-axis conversion 171 including the image processing 
circuit, and a D/A converter 110 in that order. The output signal of the 
mode change-over switch 151 is given to the vertical scanning line 
converter unit 162 and the processing circuit after time-axis conversion 
171. The output of the 14.31818-MHz (4 fsc) system clock 172 is supplied 
to the processing circuit after time-axis conversion 171. 
FIG. 69 compares one frame of the MUSE signal with one frame of the NTSC 
signal after conversion. FIG. 70 is a diagram for explaining the time-axis 
conversion memory 163, and FIG. 71 for comparing the data with the one 
horizontal period on the read side of the time-axis conversion memory. 
The vertical scanning line converter unit 162 shown in the embodiments 
27-33 converts all the effective scanning lines of the MUSE signal into 
effective scanning lines of the NTSC signal after conversion in full mode, 
and compresses the vertical direction in wide mode on the assumption of 
full-mode conversion. As a result, the time-axis conversion (in horizontal 
direction) is required to be effected in such a manner as to secure the 
roundness including 12/11 of the MUSE signal. When calculations are made 
in horizontal direction in such a manner as to secure an effective aspect 
ratio of the NTSC signal in full or wide mode, the number of points for 
one horizontal line is 910 against 748 points of the effective horizontal 
data. In the case where the horizontal system frequency is increased to 
four times of the subcarrier of the NTSC chroma signal with 910 points and 
525 lines, the vertical frequency is 59.94 Hz which fails to match with 
the vertical frequency 60 Hz of the MUSE signal. In this case, the problem 
is that the interlace is not maintained or the upper portion in vertical 
direction is distorted. In view of this, if the number of points for one 
horizontal line is rendered 909 and the system clock frequency four times 
of the subcarrier of the chroma signal of the NTSC signal, then the 
vertical frequency can be approximated infinitely to 60 Hz, thereby 
securing the interlace while eliminating the vertical upper curve. This 
manner is shown in FIG. 69. On the left is shown one frame of the MUSE 
signal, and on the right one frame after conversion. The one-frame 
conversion error is 0.01% which falls sufficiently in a practical range. 
Since the post-conversion system clock is selected at four times of the 
subcarrier of the NTSC chroma signal, it is equal to the system clock for 
digital processing at the NTSC monitor or a multiple of the subcarrier, 
and the system connection is satisfactory, thereby suppressing the 
interference due to the clock high frequency signal or the beat signal. 
Also, in view of the fact that the system clock is selected at a level four 
times of the subcarrier (hereinafter referred to as fsc) of the chroma 
signal of the NTSC signal, the reading of the data written in the 
time-axis conversion memory at 32.4-MHz by the signal multiplexer circuit 
170 shown in the embodiments 34 and 35 requires the clock rate of 
28.63636-MHz (8 fsc) which is twice of the frequency of 14.31818-MHz as 
shown in FIG. 70. The data of one horizontal data thus written, as shown 
at the top of FIG. 71, has 1124 points, which cannot be read with 909 
points per horizontal period. Therefore, the clock is doubled, for 
example, to 1818 in horizontal direction for the purpose of reading, and 
the data thus read is converted to a system clock thereby to perform the 
time-axis conversion. 
Embodiment 37: 
Now, an embodiment 37 (claim 40) will be explained. FIG. 72 is a block 
diagram showing the configuration of an M-N converter according to this 
embodiment. The configuration according to this embodiment comprises an 
input signal processing circuit 131, a vertical scanning line converter 
unit 162 shown in the embodiments 27-33, a signal multiplexer circuit 170 
shown in the embodiments 34 and 35, a time-axis conversion memory 163, a 
processing circuit after time-axis conversion 171 including an image 
processing circuit, and a D/A converter 110 arranged in that order. The 
output signal of the 10.738635-MHz (3 fsc) system clock 173 is supplied to 
the processing circuit after time-axis conversion 171. 
Next, the operation will be explained. FIG. 73 is a diagram showing the 
total number of points and the number of effective points per horizontal 
period in zoom mode, and FIG. 74 a diagram for explaining the time-axis 
conversion memory 163 in zoom mode. In zoom mode, in view of the fact that 
the number of effective scanning lines of the MUSE signal has been 
converted to 483 (the effective number of total NTSC signal scanning 
lines) at the vertical scanning line converter unit 162 shown in the 
embodiments 27-33, the number must be increased by a factor of 4/3 in 
order to maintain the roundness on the 4:3 NTSC monitor. In the case where 
the total number of points for the horizontal direction is selected to be 
909 in full or wide mode and the system frequency to be 14.31818-MHz as 
shown in the embodiment 36, the system clock is set to 3/4 times or 
10.738635 MHz which is three times of that for the subcarrier of the 
chroma signal of NTSC format in zoom mode. In this case, as shown in FIG. 
73, the total number of points for each horizontal period is 682 with an 
effective horizontal data of 561. This represents 3/4 of the points for 
the horizontal period in full or wide mode. In zoom mode, the effective 
data is 561 points, which is smaller than that For full or wide mode. The 
data therefore may be dropped off on one or both sides of horizontal 
period on write side of the time-axis conversion memory 163, while all the 
data are written as in full or wide mode and read out in a designated 
range. By so doing, all the data can be selected by the user even when the 
screen is stationary with the memory write operation stopped, for example. 
Also, the read clock of the time-axis conversion memory 163 is written in 
multiplex at the signal multiplexer circuit 170 shown in the embodiments 
34 and 35. For the data of both the luminance signal and the two color 
difference signals to be read out during one horizontal period, therefore, 
clocks of twice the system clocks are required, i.e., clocks of 
21.47727-MHz six times of that of the subcarrier of the NTSC chroma as 
shown in FIG. 74. In this way, since the system clocks are selected to a 
multiple of the subcarrier of NTSC chroma as in the embodiment 36, a 
superior coupling with the system is secured after M-N conversion, thereby 
suppressing the interference due to clock high harmonics or beat signals. 
Embodiment 38: 
Now, an embodiment 38 (claim 41) will be explained. FIG. 75 is a block 
diagram showing the configuration of an M-N converter according to this 
embodiment. This embodiment comprises an input signal processing circuit 
131, a vertical scanning line converter unit 162 shown in the embodiments 
27-33, a signal multiplexer circuit 170 shown in the embodiments 34 and 
35, a time-axis conversion memory 163, a processing circuit after 
time-axis conversion 171 including an image processing circuit, and a D/A 
converter 110 arranged in that order. The embodiment further comprises an 
85.90908-MHz (24 fsc) oscillator 174 for generating clocks after time-axis 
conversion, a 14.31818-MHz (3 fsc) system clock 172 after time-axis 
conversion supplied with the output signal of the 85.90908-MHz oscillator 
174, and a 10.738635-MHz (3 fsc) system clock 173 after time-axis 
conversion. One of the output signals of these component parts is selected 
by a 2-1 selector S.sub.15 and given to the processing circuit after 
time-axis conversion 171. A mode change-over switch 151 gives a control 
signal to the 2-1 selector S.sub.15 and the vertical scanning line 
converter unit 162. 
FIG. 76 is a block diagram showing another example of the present 
embodiment. This embodiment lacks the multiplexer circuit 170 and the 
time-axis conversion memory 163 included in the configuration of FIG. 75, 
and further comprises a luminance signal time-axis conversion memory 175 
and a color difference signal time-axis conversion memory 176 in parallel. 
Also, the 85.90908-MHz oscillator 174 is replaced by a 42.95454-MHz 
oscillator 177 as a clock generator after time-axis conversion. 
Now, the operation will be explained. Different clocks are required in 
order to maintain the roundness in full, wide and zoom modes as explained 
with reference to the embodiments 36 and 37. In the conventional M-N 
converter, two system clocks are generated by an oscillator and switched 
to meet this requirement. According to this embodiment, clocks in a common 
multiple of the 14.31818-MHz (4 fsc) system clock for full and wide modes 
and the 10.738635 MHz (3 fsc) system clock for zoom mode shown in the 
embodiments 36 and 37 are oscillated by an oscillator and 
frequency-divided to provide a system clock. In the case shown in FIG. 75, 
the signal multiplexer circuit 170 shown in the embodiments 34 and 35 is 
used. As the read clocks for the time-axis memory, therefore, 28.63636-MHz 
(8 fsc) is required for full and wide modes, and 21.47727-MHz (6 fsc) for 
zoom mode. As a result, the minimum common multiple of the two, that is, 
24 fsc or 85.90908-MHz is oscillated and frequency-divided to provide a 
system clock, so that the divided frequencies are switched or the 
frequency dividing ratio is switched according to the mode to provide a 
system clock. In the circuit blocks of FIG. 76, since the luminance signal 
time-axis conversion memory 175 and the color difference signal time-axis 
conversion memory 176 are used, the read clock for the time-axis memories 
is same as the system clock. Therefore, the frequency of 42.95454-MHz (12 
fsc) which is the minimum common multiple of the two system clocks is 
oscillated by an oscillator and frequency-divided, so that, the divided 
frequencies are switched or the frequency-dividing ratio is changed to 
provide a system clock. Because of this configuration, only one oscillator 
suffices and the same can be said of the VCXO used for PLL applied on the 
MUSE signal clock of 32.4-MHz. 
Embodiment 39: 
An embodiment 39 (claim 42) will be explained. FIG. 77 is a block diagram 
showing the configuration of an M-N converter according to this 
embodiment. This embodiment comprises an input signal processing circuit 
131 for subjecting the MUSE signal to input processings, a vertical 
scanning line converter unit 162 shown in the embodiments 27-33, a signal 
multiplexer circuit 170 shown in the embodiments 34 and 35, a time-axis 
conversion memory 163, a signal separator circuit 178 for separating the 
signal multiplexed by the signal multiplexer circuit 170 into the 
luminance signal and the color difference signal, a signal separator/3-4 
data converter circuit 179 for separating the multiplexed signal and 
generating four data from the three data with the luminance signal and the 
color difference signal, an image processing circuit 136, a mode 
change-over switch 151, and a 14.31818-MHz (4 fsc) system clock 172 after 
time-axis conversion. The output signal of the time-axis conversion memory 
163 is supplied to the signal separator circuit 178 and the signal 
separator/3-4 data converter circuit 179, the output signals of which are 
selectively supplied to the image processing circuit 136 through a 2-1 
selector S.sub.16. The output signal of the mode change-over switch 151 is 
supplied to the 2-1 selector S.sub.16 and the vertical scanning line 
converter unit 162. The output signal of the 14.31818-MHz (4 fsc) system 
clock 172 is supplied to the signal separator 178, the signal 
separator/3-4 data converter 179 and the image processing circuit 136. 
Now, the operation will be explained. FIG. 78 shows a model of sampling 
points for explaining the operation of the 3-4 data converter circuit. In 
the conventional M-N converter, the system clock after time-axis 
conversion is switched among operations in full, wide mode and zoom mode. 
According to the present embodiment, in order to solve this inconvenience, 
the signal is processed differently among full, wide and zoom modes. 
Especially in zoom mode, three data are linearly interpolated at adjacent 
several points thereby to generate four data and thus unify the system 
clock by horizontal expansion. The input signal is processed at the input 
signal processing circuit 131, the scanning lines are converted at the 
vertical scanning line converter unit 162 according to the particular mode 
and the resulting data is written in the time-axis conversion memory 163. 
In full or wide mode, the signal is separated into the luminance signal 
and the color difference signal by the signal separator 178 operated in 
accordance with the 14.31818-MHz (4 fsc) system clock 172. In zoom mode, 
on the other hand, the signal is passed through another route and 
processed by the signal separator/3-4 data converter circuit 179. This 3-4 
data converter circuit 179, as shown in FIG. 78, generates 748 points of 
data by linear interpolation frm 561 points of zoom-mode data read from 
the time-axis conversion memory 163 for the luminance signal Y, for 
example. In zoom mode, horizontal multiplication by a factor of 4/3 is 
required for maintaining the roundness as described above with reference 
to the embodiment 37. For this reason, according to the conventional 
system, the system clock is multiplied by 3/4 and expanded horizontally, 
whereas according to the present embodiment, three data are linearly 
interpolated at adjacent several points into four data and the horizontal 
length is increased by 4/3 to maintain the roundness. The mode change can 
be performed by appropriately switching the outputs of the signal 
separator/3-4 data converter circuit 179 and the signal separator circuit 
178 according to the particular mode, thereby making it possible to 
operate the system with a single clock. This configuration requires a 
single system clock of 14.31818-MHz (4 fsc) with a single oscillator. 
This, together with the fact that the system clock is single and four 
times of the chroma signal subcarrier frequency, permits a satisfactory 
system matching with the NTSC signal processing stages connected next, to 
the M-N converter. Thus digital coupling is facilitated while at the same 
time suppressing interferences. 
Also, apart from the method as shown in FIG. 78 in which four-point data 
are generated from 3-point data by the simplest, linear interpolation 
between two points, the use of more points with a complicated coefficient 
for linear interpolation will prevent the degradation of frequency 
characteristics which otherwise might occur due to the linear 
interpolation. According to the embodiment under consideration, the three 
modes including full, wide and zoom are handled with a single system 
clock, and therefore the 3-4 data conversion is involved for zoom mode. In 
a method for expanding by about 8/7 horizontally, however, the horizontal 
expansion can be realized by a single system clock when the linear 
interpolation circuit is so changed as to generate eight from seven data. 
Embodiment 40: 
Now, an embodiment 40 (claim 43) will be explained. FIG. 79 is a block 
diagram showing the configuration of an M-N converter according to this 
embodiment. This embodiment Further comprises a horizontal high-frequency 
component compensator circuit 180 added in series with the signal 
separator/3-4 data converter circuit 179 in the block diagram of FIG. 77 
according to the embodiment 39. 
The operation of this embodiment will be explained. In the method according 
to the embodiment 39 where three data are linearly interpolated to 
generate four data by the signal separator/3-4 data converter circuit and 
the roundness is thus maintained by horizontal expansion with a single 
system clock in zoom mode as described above, the horizontal frequency 
characteristic is deteriorated at the time of linear interpolation of 
three data. A method is available for compensating for this disadvantage 
by linear interpolation using a complicated coefficient at a multiplicity 
of points. This method, however, has the disadvantage of an increased 
circuit size. This disadvantage is overcome by adopting a method of very 
simple linear interpolation as shown in FIG. 78 of the embodiment 39 in 
which the 3-4 data conversion is performed by linear interpolation between 
two points with a horizontal high-frequency component compensator circuit 
180 inserted in series. This configuration permits the high-frequency 
component compensation with complicated linear interpolation to be 
replaced by a simple high-frequency component compensator circuit, with a 
simple linear interpolation, thereby preventing the circuit from 
increasing in size. Unlike in the block configuration according to this 
embodiment having an independent horizontal high-frequency component 
compensator circuit, the contour correction circuit of the image 
processing circuit 136 connected in the subsequent stage can double as a 
horizontal high-frequency component compensator circuit with equal effect. 
In this case, the requirement for high-frequency component compensation in 
zoom mode can be met by differentiating the gain of contour correction 
from those for the other modes (full and wide). 
Embodiment 41: 
An embodiment 41 (claim 44) will be explained. According to this 
embodiment, the signal multiplexer circuit 170 is configured as shown in 
FIG. 66. FIG. 80 is a timing chart for explaining the embodiment. 
In the case where a single system clock after time-axis conversion is used 
with the 3-4 data converter circuit 179 shown according to the embodiment 
39 in zoom mode, the time-axis conversion memory 163 requires 681 points 
of effective data for each horizontal period. For this to be realized in 
the simplest fashion, 681 out of 748 points of effective data per 
horizontal period are written as an input to the time-axis conversion 
memory 163, from which three data are read while leaving one data not 
read. This method can be realized when writing into the time-axis 
conversion memory 163 after multiplexing by the signal multiplexer circuit 
170 shown in the embodiment 34. In this method, however, the position for 
zoom mode cannot be changed when the screen is inhibited from write 
operation and set in stationary state. According to this embodiment, in 
order to solve these problems, all horizontal data are written in the 
time-axis conversion memory through the multiplexer circuit shown in the 
embodiment 35, and in the read operation, nine data are read out in 681 
points in 16 cycles as shown in the timing chart of FIG. 80, while 
extraneous data are collectively read out during the blanking period. In 
this way, the read position is changed in horizontal direction even during 
stationary state, thereby making the output range in zoom mode variable. 
The operation of reading out nine data in 16 cycles can be easily 
performed by controlling the read enable of the time-axis conversion 
memory 163 as shown in the timing chart of FIG. 80. 
Embodiment 42: 
Now, an embodiment 42 (claim 45) will be explained. FIG. 81 is a block 
diagram showing the configuration of an M-N converter according to the 
present embodiment. This embodiment comprises an input signal processing 
circuit 131 for subjecting the MUSE signal to input processings, a 
vertical scanning line converter unit 162 shown in the embodiments 27-33, 
a signal multiplexer circuit 170 shown in the embodiments 34 and 35, a 
time-axis conversion memory 163, a signal processing circuit 182 for 
processing the output of the time-axis conversion memory shown in the 
embodiments 36-41, an image processing circuit 136 and D/A converters 110, 
110. 
The image processing circuit 136 includes a nonlinear correction ROM 183 
for improving the linearity of the luminance signal supplied from the 
signal processing circuit 182, a Y image processing circuit 184 for 
contour correction, blanking and other processing of the luminance signal 
outputted from the nonlinear correction ROM 183, a transmission inverse 
gamma correction ROM 185 for subjecting the color difference signal from 
the signal processing circuit 182 to inverse gamma operation, and a color 
difference signal image processing circuit 186 for performing such 
processings as blanking and contour correction of the color difference 
signal supplied from the transmission inverse gamma correction ROM 185. 
The signal outputted from the mode change-over switch 151 is given to the 
vertical scanning line converter unit 162 and the signal processing 
circuit 182. Further, the clock signal outputted from the system clock of 
14.31818-MHz (4 fsc) system clock 172 which is a system clock after 
time-axis conversion is supplied to the signal processing circuit 182, the 
Y image processing circuit 184 and the color difference signal image 
processing circuit 186. 
The operation of this embodiment will be explained. In the conventional M-N 
converter, the MUSE signal has a substantially linear characteristic as 
the inverse gamma and transmission gamma of the camera are approximated in 
characteristics, and therefore the transmission inverse gamma and the 
display gamma are not employed for reducing the circuit size. The 
transmission inverse gamma for the color difference signal, on one hand, 
for its theoretical simplicity and effect, is sometimes introduced with a 
ROM and an arithmetic circuit. (Reference: "MUSE High Definition TV 
Transmission System", compiled by The Institute of Electronics, 
Information and Communication Engineers). With regard to the luminance 
signal, however, the signal is required to be subjected to display gamma 
by returning to R, G, B after transmission inverse gamma. The reconversion 
of the R, G, B signals to the luminance signal or the color difference 
signal is not in current practice as it increases the circuit size and 
thereby deteriorates the Y gradation characteristics by the amount 
equivalent to the difference of inverse gamma and transmission gamma at 
the transmitting side. The embodiment under consideration, in order to 
obviate this problem, is intended to improve the gradation characteristic 
of the luminance signal by generating a characteristic approximated by the 
transmission inverse gamma and display gamma of the luminance signal 
through the ROM or the arithmetic circuit and applying it to the luminance 
signal. As shown in FIG. 81, the Y nonlinear correction ROM approximated 
with the Y transmission inverse gamma and the display gamma calculated in 
advance is inserted in the Y output of the signal processing circuit 82 
after time-axis conversion thereby to improve the gradation characteristic 
of the luminance signal. Since a theoretically accurate ROM cannot be 
fabricated, the Y linearity is consciously changed and a nonlinear 
characteristic having a visual effect on the screen is generated to be 
usable by switching. The above-mentioned configuration makes it possible 
to improve the gradation characteristic of the luminance signal simply by 
increasing the circuit size to some degree. 
As this invention may be embodied in several forms without departing from 
the spirit of essential characteristics thereof, the present invention is 
therefore illustrative and not restrictive, since the scope of the 
invention is defined by the appended claims rather than by the description 
preceding them, and all changes that fall within metes and bounds of the 
claims, or equivalence of such metes and bounds thereof are therefore 
intended to be embraced by the claims.