Video cassette recorder having variable, high-resolution video screen zooming

A video cassette recorder has a video screen zooming function, capable of zooming an optional region of one of plural still pictures sequentially displayed on a screen, as one picture. A digital signal processing unit converts composite video signals into digital video signals and a first memory unit stores the digital video signals by frames. A zoom signal processing unit zooms only digital video signals corresponding to a predetermined zoom region from the digital video signals so as to reconfigure them as digital video signals corresponding to one frame. A second memory unit stores the zoomed digital video signals by frames. A first switch selects the digital video signals from the first memory unit in a stop mode or digital video signals from the second memory unit in a zoom mode. Under a control of a control signal generating unit, an RGB matrix circuit reconfigures the digital video signals from the first switch unit as R, G and B color analog signals, and a second switch selects and outputs original composite video signals in a playback mode and outputs signals from the RGB matrix circuit in the stop mode or the zoom mode, under control of the control signal generating unit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to video cassette recorders, and more 
particularly to a video cassette recorders having a video screen zooming 
function, capable of zooming a selectable region of one of plural still 
pictures sequentially displayed on a screen, as one picture and of 
improving the resolution of the zoomed picture, 
2. Description of the Prior Art 
Conventional video cassette recorders (VCRs) with a zooming function have 
limitations on regions to be zoomed and a zoom size and thereby have 
limited variety of zooming. Since the sampling intervals are extended upon 
zooming in conventional VCRs, a zoomed picture is mosaicked, thereby 
causing the resolution to be degraded. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the above circumstances and 
has as an object to provide a video cassette recorder with a video screen 
zooming function, that is capable of zooming a selectable region of plural 
one of still pictures sequentially displayed on a screen, as one picture 
and of improving the resolution of the zoomed picture. 
Additional objects and advantages of the invention will be set forth in 
part in the description which follows and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and attained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims. 
To achieve the objects and in accordance with the purpose of the invention, 
as embodied and broadly described herein, a video cassette recorder of 
this invention comprises digital signal processing means for receiving 
composite video signals in a stop mode and converting the composite 
signals into digital video signals. First memory means are provided for 
receiving the digital video signals from the digital signal processing 
means and for storing the digital video signal by frames. 
Control signal generating means are provided for receiving signals for 
operation modes of the video cassette recorder and generating first to 
third control signals corresponding to the received signals. Zoom signal 
processing means receive digital video signals corresponding to one frame 
from the first memory means, according to the third control signal 
generated in the control signal generating means in a zoom mode and 
zooming only digital video signals corresponding to a predetermined zoom 
region from the received digital video signals, so as to reconfigure them 
as digital video signals corresponding to one frame. Second memory means 
receive the zoomed digital video signals from the zoom signal processing 
means and store them by frames therein. First switch means select the 
digital video signals corresponding to one frame from the first memory 
means in the stop mode and digital video signals corresponding to one 
frame from the second memory means in the zoom mode, according to the 
first control signal from the control signal generating means. A RGB 
matrix circuit receives digital video signals corresponding to one frame 
via the first switch means and reconfigures them as R, G and B color 
analog signals. Second switch means for selecting and outputs original 
composite video signals in a playback mode and outputs signals from the 
RGB matrix circuit in the stop mode or the zoom mode, according to the 
second control signal of the control signal generating means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, there is shown a block diagram of a VCR with a video 
screen zooming function in accordance with the present invention. 
As shown in FIG. 1, the VCR comprises a digital signal processing unit 100 
for receiving composite video signals VIDEO IN in a stop mode and 
converting them into digital video signals and a first memory unit 200 for 
receiving the digital video signals from the digital signal processing 
unit 100 and storing them by frames therein. In accordance with the 
present invention, the VCR also comprises a zoom signal processing unit 
300 for receiving digital video signals corresponding to one frame from 
the first memory unit 200 and zooming only digital video signals 
corresponding to a predetermined zoom region from the received digital 
video signals, so as to reconfigure them in the form of digital video 
signals corresponding to one frame. The operation of the zoom signal 
processing unit 300 is controlled by a third control signal CS.sub.3 
outputted from a control signal generating unit 600, in a zoom mode. The 
control signal generating unit 600 is adapted to receiver external signals 
SIGNAL IN for respective operation modes of the VCR and to output 
corresponding first to third control signals CS.sub.1 to CS.sub.3. A 
second memory unit 400 is also provided to receive the zoomed digital 
video signals from the zoom signal processing unit 300 and store them by 
frames therein. The VCR further comprises a first switch unit SW.sub.1 for 
selecting output signals from the first memory unit 200 in the stop mode 
and output signals from the second memory unit 400 in the zoom mode, 
according to the first control signal CS.sub.1 from the control signal 
generating unit 600. A RGB matrix circuit 500 is provided for receiving 
digital video signals corresponding to one frame via the first switch unit 
SW.sub.1 and reconfiguring them in the form of R, G and B color analog 
signals. A second switch unit SW.sub.2 is provided for selecting and 
outputting original composite video signals in a playback mode and output 
signals from the RGB matrix circuit 500 in the stop mode or the zoom mode, 
according to the second control signal CS.sub.2 of the control signal 
generating unit 600. 
FIG. 2 is a circuit diagram of the VCR shown in FIG. 1. 
As shown in FIG. 2, the digital signal processing unit 100 comprises a 
synchronous signal separation circuit 110 for receiving composite video 
signals VIDEO IN and separating synchronous signals from the composite 
video signals VIDEO IN. The separated synchronous signals are adapted as 
reference signals for subsequently processing the composite video signals 
VIDEO IN. The digital signal processing unit 100 also comprises an analog 
decoder 120 that receives the composite video signals VIDEO IN and the 
synchronous signals from the synchronous signal separation circuit 110 and 
separates them into luminance signals Y and color difference signals U and 
V (U.ident.R-Y and V.ident.B-Y) using the synchronous signals as reference 
signals and a signals. A PLL circuit 130 receives the color difference 
signals U and V as vector phase signals from the analog decoder 120 and 
the synchronous signals from the synchronous signal separation circuit 110 
and converts the color difference signals U and V into analog signals. An 
analog/digital converter 140 receives analog luminance signals Y from the 
analog decoder 120 and the analog color difference signals U and V from 
the PLL circuit 130 and converts them into digital luminance signals Y' 
and digital color difference signals U' and V'. A clock generator 150 also 
sends clock signals to the PLL circuit 130. 
The first memory unit 200 comprises a counter 210 for receiving and decimal 
counting output signals from the analog/digital converter 140 of the 
digital signal processing unit 100. A frame memory 220 for receives output 
signals from the counter 210 and stores them by frames. The first memory 
unit 200 also comprises a counter 230 that receives the clock signals from 
the clock generator 150 of the digital signal processing unit 100 and 
controls write and read operations of the frame memory 220 according to 
the clock signals. 
The zoom signal processing unit 300 comprises a zoom region position 
controller 310 that receives the digital video signals corresponding to 
one frame from the frame memory 220. The zoom region position controller 
310 controls positions of dots generated according to the third control 
signal CS.sub.3 from the control signal generating unit 600. A zoom scale 
controller 320 receives data DATA IN applied externally and outputs zoom 
scale factors that determine the area of a zoom window. An edge bar 
generator 330 receives output signals from the zoom scale controller 320 
and generates edge bars to form the zoom window according to the received 
signals. The zoom signal processing unit 300 further comprises a zoom 
region size controller 340 for zooming digital video signals corresponding 
to one frame in the zoom window formed by the edge bar generator 330 
according to the zoom scale factors outputted from the zoom scale 
controller 320. A simulator 350 receives the video signals corresponding 
to one frame from the zoom region size controller 340 and takes average 
values of data for adjacent pixels and interpolates them. A pulse 
generator 360 sends pulse signals to the zoom scale controller 320, the 
zoom region position controller 310 and the simulator 350. 
The second memory unit 400 comprises a counter 410 for receiving and 
decimal counting zoomed video signals from the simulator 350 of the zoom 
signal processing unit 300. A frame memory 420 receives the video signals 
from the counter 410 and stores them by frames. In addition, a counter 430 
receives output signals from the pulse generator 360 and controls write 
and read operations of the frame memory 420 according to the received 
signals. 
Now, operation of the VCR with the above-described construction according 
to the present invention will be described. 
In the playback mode of the VCR, the composite video signals VIDEO IN are 
outputted in the form of original composite signets without being 
digitally processed, via the second switch unit SW.sub.2, according to the 
second control signal CS.sub.2 outputted from the control signal 
generating unit 600. Accordingly, reproduced pictures are continuously 
displayed on a TV screen at a normal rate. 
When a signal for the stop mode is applied during the playback operation of 
the VCR, the composite video signals VIDEO IN are applied to the analog 
decoder 120 in which the composite video signals VIDEO IN are separated 
into luminance signals Y and color difference signals U and V with vector 
phase angles, 
The composite video signals VIDEO IN are also inputted to the synchronous 
signal separation circuit 110 in which synchronous signals are separated 
from the composite video signals VIDEO IN. The separate synchronous 
signals are applied to the decoder 120 and the PLL circuit 130 as 
reference signals. 
The luminance signals Y separated from the composite video signals VIDEO IN 
by the analog decoder 120 are directly applied to the analog/digital 
converter 140 and then converted into digital luminance signals Y'. On the 
other hand, the color difference signals U and V with vector phase angles 
are processed as analog signals in the PLL circuit 130. Resultant analog 
color difference signals U and V are then applied to the analog/digital 
converter 140 and then converted into digital color difference signals U' 
and V'. 
That is, the analog/digital converter 140 quantizes the received analog 
video signals Y, U and V with predetermined sampling frequencies and thus 
outputs digital video signals Y', U' and V' each having n bits. The 
digital video signals Y', U' and V' are applied to the counter 210 of the 
first memory unit 200. 
The PLL circuit 130 of the digital signal processing unit 100 controls the 
color difference signals U and V, using the separated synchronous signals 
separated from the synchronous signal, separation circuit 110 as reference 
signals. Clock signals required for the PLL control are supplied from the 
clock generator 150. 
The digital video signals Y', U' and V' are decimal-counted and then 
sequentially stored by frames in the frame memory 220. The counter 230 
receives clock signals from the clock generator 150 and thereby controls 
the write and read operations of the frame memory 220. 
The first switch unit SW.sub.1 is connected to an output terminal of the 
frame memory 220 of the first memory unit 200 in the stop mode of VCR, 
according to the first control signal CS.sub.1 outputted from the control 
signal generating unit 600. The digital video signals stored by frames in 
the frame memory 220 are acordingly applied to the ROB matrix circuit 500 
via the first switch SW.sub.1. The RGB matrix circuit 500 reconfigures the 
digital video signals Y', U' and V' received therein and outputs analog 
color signals R, G and B. 
In the stop mode or the zoom mode other than the normal playback mode, the 
control signal generating unit 600 (FIG. 1) outputs the second control 
signal CS.sub.2, so that the second switch SW.sub.2 is connected to an 
output terminal of the RGB matrix circuit 500. As a result, the video 
signals outputted from the ROB matrix circuit 500 are processed as a still 
frame and then displayed on a TV screen. 
The zooming operation of the zoom signal processing unit 300 will be now 
described. 
When the user wants to zoom a desired region of a still picture displayed 
on the TV screen, as shown in FIG. 3, a zoom mode signal is input to the 
VCR by operating on a corresponding key. In response to the inputted zoom 
mode signal, the control signal generating unit 600 outputs the third 
control signal CS.sub.3. Accordingly, dots each having a size of 6 lines 
.times.18 pixels are displayed on the screen and the coordinates of dots 
are stored in the form a matrix. 
In case of a screen of the system with 700 pixels .times.287 lines, the 
coordinates (n,m) of dots are defined such that n is 0 to 40 and m is 0 to 
30. In this case, the coordinates of dots have the matrix form of 
40.times.30. 
When external data about dot position is inputted under the condition that 
dots have been displayed on the screen, the zoom position controller 310 
displays dots on corresponding positions of the screen. Then, the zoom 
scale controller 320 determines the size the zoom window based on the 
inputted external data. Following the operation of zoom scale controller 
320, the edge bar generator 330 generates an edge bar on a still picture 
displayed on the screen, so as to form the zoom window. 
In case of the system screen with 700 pixels (H).times.287 lines (L), 
the edge bar is displayed to have an outline thickness of 3 lines .times.6 
pixels. The zoom window has an aspect ratio of 4.times.3 identical to 
those of TV screens. This zoom window can be enlarged at the aspect ratio 
of 4.times.3, based on scale factors. 
FIGS. 5a to 5c are schematic views illustrating the procedures of zooming 
video signals in the zoom window by the zoom region size controller 340, 
based on zoom scale factors. FIG. 5A shows the relation that position 
values in the zoom window correspond to pixel data D.sub.x.y in the 
memory, respectively. In case of data of 64.times.64 pixels, the position 
data n1m1 corresponds to the pixel data D.sub.1.1, the position data n1m2 
the pixel data D.sub.1.64, the position data n2m1 the pixel data 
D.sub.64.1, and the position data n2m2 the pixel data D.sub.64.64. 
Where pixel data corresponding to the matrix position values are double 
zoomed, as shown in FIG. 5a, the addresses 4000H to 4FFFH for pixel data 
in the memory are converted into addresses 8000H to 8FFFH by a refresh 
memory in the zoom region size controller 340. Accordingly, the pixel data 
is zoomed as shown in FIG. 5b. 
The pixel data double zoomed is then applied to the simulator 350. The 
simulator 350 interpolates adjacent pixel data, to achieve a 
reconfiguration of pixel data as shown in FIG. 5c. 
The interpolation is carried out by taking average values of adjacent pixel 
data. For example, new pixel data obtained by the interpolation are 
D'.sub.1.1 =(D.sub.1.1 +D.sub.1.2)/2, D".sub.1.1 =(D.sub.1.1 
+D.sub.2.1)/2, and D"'.sub.1.1 =(D.sub.1.1' +D.sub.2.1')/2. 
The video signals Yz', Uz', and Vz' zoomed, as indicated above, are applied 
to the second memory unit 400. The counter 410 of second memory unit 400 
decimal-counts the zoomed video signals Yz', Uz', and Vz' so that they can 
be stored by frames in the frame memory 420. 
In the zoom mode of the VCR, the first switch unit SW.sub.1 is connected to 
an output terminal of the frame memory 420 of the second memory unit 400, 
according to the first control signal CS.sub.1 outputted from the control 
signal generating unit 600. Accordingly, the zoomed digital video signals 
Yz', Uz' and Vz' stored in the frame memory 420 are applied to the RGB 
matrix circuit 500 via the first switch SW.sub.I. The RGB matrix circuit 
500 reconfigures the digital video signals Y', U' and V' received therein 
and outputs analog color signals R, G and B. 
In the zoom mode, the second switch SW.sub.2 is connected to an output 
terminal of the RGB matrix circuit 500. As a result, the analog color 
signals R, G and B are outputted by frames from the RGB matrix circuit 500 
via the second switch unit SW.sub.2. Accordingly, a still picture obtained 
by zooming a picture portion of the zoom window is displayed on the TV 
screen. 
FIGS. 6a and 6b are timing diagrams illustrating filtering of video signals 
corresponding to the zoom region at one horizontal scanning interval 
F.sub.h. FIGS. 7a and 7b are timing diagrams illustrating filtering of 
video signals corresponding to the zoom region at one vertical scanning 
interval F.sub.V. On the other hand, FIGS. 8a to 8l are timing diagrams 
for explaining the interpolation of video signals by the simulator 350. 
When the quantized luminance signals Y outputted from the frame memory 220 
are filtered by luminance signal data Y.sub.0, Y.sub.1 and Y.sub.2 and 
color difference signal data U.sub.0 and V.sub.0 shown in FIGS. 8c and 8d, 
based on reference pulses generated from the pulse generator 360 shown in 
FIG. 8b, only luminance signals are interpolated by the simulator 350 in 
the horizontal scanning interval mf.sub.h for the zoom window. This 
interpolation will be now described. 
The luminance signals in the zoom window are shown in FIG. 8g. The 
simulator 350 interpolates each luminance signal in the zoom window with a 
virtual luminance signal Y.sub.0, that is, a luminance signal of adjacent 
pixel shown in FIG. 8h and thereby produces a virtual luminance signal 
shown in FIG. 8k. 
Since no interpolation is made for color difference signals, original color 
difference signals are obtained as shown in FIG. 8l. 
Upon zooming, sampling frequencies are extended together with video signals 
in the zoom window, as shown in FIG. 9a. Accordingly, video signals in 
portions to be mosaicked as shown in FIG. 9b is reconfigured by the 
simulator 350. 
As apparent from the above description, the present invention makes it 
possible to select a region to be zoomed from a picture being displayed in 
the playback mode as a desired size and zoom it as one picture. 
Accordingly, a variety of zooming is achieved. 
Since a picture is reconfigured by interpolating video signals in a zoom 
window in accordance with the present invention, the resolution can be 
improved, even though sampling intervals are increased due to zooming. In 
particular, pictures for education and research can be zoomed as still 
pictures for search with little noise. 
The foregoing description of the preferred embodiment has been presented to 
illustrate the invention. It is not intended to be exhaustive or to limit 
the invention to the form disclosed. 
In applying the invention, modifications and variations can be made by 
those skilled in the pertaining art without departing from the scope and 
spirit of the invention. It is intended that the scope of the invention be 
defined by the claims appended hereto, and their equivalents.