Interleaving/deinterleaving apparatus for a digital video cassette recorder and the method thereof

The interleaving/deinterleaving region of compressed image data is restrictively determined in accordance with a predetermined maximum speed, and interleaving/deinterleaving is performed within the restricted interleaving/deinterleaving region. Various burst and random errors can be effectively processed and corrected, especially in variable speed play since the compressed image data is stored in and read out from a memory with a different format. In recording and reproduction, the compressed image data is scanned per data segment in zigzag form and the data sequence of the input data segment is changed, resulting in interleaving being performed with data continuity maintained. Error correction capability is improved by performing outer and inner coding with respect to the interleaved data.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a digital video cassette recorder (VCR), 
and more particularly to an apparatus for and a method of 
interleaving/deinterleaving for a digital VCR which can effectively 
correct errors occurring in recording or reproduction of compressed data 
and improve error correction capability, especially in variable speed 
reproduction. 
2. Description of the Prior Art 
The errors occurring in recording and reproduction with a digital VCR may 
be classified as random errors and burst errors. Random errors 
independently occur in digital signal lines due to additive noise during 
signal processing, and burst error is successive error occurring with 
respect to a bit stream of transmission data under the influence of tape 
condition, and so on. Burst error can be corrected by being replaced with 
random errors through an interleaving/deinterleaving process. 
A conventional interleaving apparatus for a digital VCR, as shown in FIG. 
1, includes outer coder 1 for performing outer coding with respect to an 
input compressed data stream and successively outputting the data stream 
with an outer code symbol added thereto, first sector array memory 2 for 
successively storing the data outputted from outer coder 1, and inner 
coder 3 for reading the data stored in first sector array memory 2 in an 
order different from that in storing the data to first sector array memory 
2, performing inner coding, outputting and recording the data with inner 
code symbol added thereto on a tape via a head. The interleaving apparatus 
is also provided with inner decoder 4 for decoding only data having the 
inner code symbol among the data reproduced from the tape, detecting 
errors in the data and performing interleaving with respect to such 
detected errors, second sector array memory 5 for distributively storing 
the interleaved data from inner decoder 4, and outer decoder 6 for reading 
out data from second sector array memory 5 in an order different from that 
in writing the data and performing decoding with respect to data having 
the outer code symbol to correct the errors. 
In the conventional interleaving apparatus constructed as above, when the 
compressed data stream as shown in FIG. 2A is inputted, outer coder 1 
performs outer coding in a vertical direction with respect to a series of 
symbols of the input data as shown in FIG. 2B and outputs data having the 
outer code symbol. Then, a redundancy is added to the data having the 
outer code symbol as shown in FIG. 2C and the redundancy-added data is 
stored in first sector array memory 2 in the order shown in FIG. 2D. 
Inner coder 3 reads out the data from first sector array memory 2 in an 
order different from that in storing the data and performs interleaving to 
add the inner code symbol to the data. Accordingly, the order of the data 
is changed, being different from that of the input data, causing a burst 
error to be replaced by random errors. The data stream interleaved as 
described above is then inner-coded by inner coder 3, with the result that 
strong error correction coding (ECC) is performed. 
Inner decoder 4 decodes the data having the inner code symbol among the 
data having the inner and outer code symbols reproduced from the tape and 
detects and corrects the errors. That is, in correcting the errors, inner 
decoder 4 performs interleaving with respect to the errors which exist 
beyond its capability and distributively stores the interleaved data still 
having errors in second sector array memory 5. Outer decoder 6 performs 
outer decoding with respect to the data stored in second sector array 
memory 5 to correct the remaining errors, and thereby various kinds of 
errors occurring in reproduction in a digital VCR can be corrected and 
prevented. 
The conventional apparatus as described above thus provides a strong 
capability to correct various errors occurring in reproduction of data and 
is suitable for use in a digital VCR for professional purposes. 
However, in a home digital VCR, such an elaborate apparatus for strong 
error correction cannot be used due to a limitation of recording frequency 
bandwidth and high costs. 
Also, in high speed play such as a picture search mode, the VCR head, as 
shown in FIGS. 4A to 4C, passes across various tape tracks and the head 
trace region in a track, as well as the size of a sector array memory in 
the conventional apparatus, is inversely proportional to the degree of 
high speed. 
Practically, the VCR head in high speed play has a nonlinear trace as shown 
in FIG. 4C, and this causes the maximum interleaving region for ECC to be 
further restricted in comparison to the linear head trace. Also, in high 
speed play, the head continually passes the track portion of the same 
position due to the restricted interleaving region, and the image data of 
the same picture portion is extracted. Accordingly, in order to obtain the 
image data of other picture portions, data allocation for rearranging the 
data recording position is required. 
Further, when a signal is recorded on a tape track by the conventional 
apparatus as shown in FIG. 10A, a redundancy is added to the signal, 
utilizing a two-dimensional Reed-Solomon code for correcting various kinds 
of burst and random errors. Thus, in normal reproduction of the signal, 
the decoding array is fully occupied with information data and the 
2-dimensional Reed-Solomon decoding can be performed. 
However, in a special reproduction such as a high speed play, only a 
portion of the track can be traced, and thus the decoding array is 
partially occupied with information data and only one-dimensional error 
decoding can be used, causing the confidence in correcting the errors to 
deteriorate. 
Meanwhile, the data segments reproduced by the conventional apparatus are 
classified into complete segments and incomplete segments, and the data 
segment is composed of slices which are the variable unit in which the 
image data and other information are compressed and compacted. 
Accordingly, as shown in FIG. 15, several slices may exist in the K-th 
segment while a slice may exist over two segments as shown in (k+1)-th 
segment. 
Such slices may be performed with variable length coding (VLC) or 
compressed at different rates in encoding a high quality image or a normal 
image. Thus, the lengths of the respective compressed data streams may 
appear to be different from one another, even though the respective image 
information of the same amount are compressed. Accordingly, in order to 
perfectly perform the variable length decoding (VLD) in a decoder, a 
complete bit stream should be reproduced in the unit of slice. 
According to the conventional apparatus, however, groups of complete and 
incomplete segments are placed in the detected area as shown in FIG. 16 
when the reproduced data stream has been deinterleaved in variable speed 
play. If the slices, being the unit of data compaction, exist over 
incomplete segments excluding the group of complete segments, such slices 
in the incomplete segments will be of no use, inviting data loss. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an 
interleaving/deinterleaving apparatus for a digital VCR and the method 
thereof which can effectively correct various kinds of burst and random 
errors in recording/reproduction of compressed data. 
It is another object of the present invention to provide an 
interleaving/deinterleaving apparatus for a digital VCR and the method 
thereof which makes it possible to effect maximum 
interleaving/deinterleaving within a predetermined high speed by 
determining an interleaving/deinterleaving region in accordance with the 
predetermined high speed and by performing interleaving/deinterleaving 
within the determined interleaving/deinterleaving region. 
In order to achieve the above objects, there is provided an 
interleaving/deinterleaving apparatus for a digital VCR which comprises: 
interleaving/deinterleaving control means for restrictively determining an 
interleaving/deinterleaving region in accordance with a predetermined 
maximum speed in recording/reproduction of compressed image data; 
memory means for storing and reading out said compressed image data in a 
specific format under the control of said interleaving/deinterleaving 
control means; and 
means for performing interleaving/deinterleaving with respect to said 
compressed in age data provided from said memory means. 
Also, in order to achieve the above objects, there is provided an 
interleaving/deinterleaving method for a digital VCR which comprises the 
steps of: 
dividing an input compressed data stream into a synchronizing signal and 
data and formatting the data in the unit of segment; 
reading the formatted data segments in zigzag form and storing the read 
data segments in a memory mapper; 
dividing each of the data segments stored in the memory mapper into n 
segment blocks and successively writing the segment blocks in a data field 
with shifting each of the segment blocks for one vertical size of the data 
segment; and 
performing inter-symbol interleaving with respect to data symbols in the 
segment blocks by classifying the data symbols and sectioning the 
classified data symbols in line.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 3 shows an embodiment of the interleaving/deinterleaving apparatus for 
a digital VCR according to the present invention. The apparatus comprises 
source encoder 10 for encoding an input image data stream, memory mapper 
20 for storing and reading out the image data stream encoded by source 
encoder 10 in the unit of segment, interleaving controller 30 for 
restricting an interleaving region in accordance with a header information 
in line with a predetermined maximum speed, inter-segment interleaver 40 
for performing inter-segment interleaving with respect to segments of the 
image data stream provided from memory mapper 20, outer encoder 50 for 
performing outer encoding with respect to the image data stream from 
inter-segment interleaver 40, intra-segment interleaver 60 for performing 
intra-segment interleaving with respect to the segments of the image data 
stream from outer encoder 50, and inner encoder 70 for performing inner 
encoding with respect to the image data stream from intra-segment 
interleaver 60. 
A video head may pass through many more tracks as shown in FIG. 4A in high 
speed play such as in picture search mode than in normal speed play as 
shown in FIG. 4B and thus substantially much data in the track cannot be 
read out. Accordingly, errors occur and propagate due to the unread data 
so that even a powerful ECC may not function. 
Thus, the maximum interleaving region should be smaller than the area of 
the track trace covered by the head in the maximum speed mode of the VCR, 
wherein the region is obtained by the following expression 
##EQU1## 
where S (0.ltoreq.S.ltoreq.1) is an interleaving region, N is the maximum 
speed in reproduction, and TD (0.ltoreq.TD.ltoreq.1) is a track deviation 
degree. 
In this embodiment, after source encoder 10 encodes an input digital data 
stream and provides the data stream as shown in FIG. 5A, memory mapper 20 
divides the data stream in the unit of segment as shown in FIG. 5B and 
stores the divided data stream. At this time, interleaving controller 30 
provides to memory mapper 20 a control signal for determining an 
interleaving region in accordance with a VCR status signal and ID 
information in line with the above expression and performing interleaving 
within the determined region, thereby preventing the reduction of 
interleaving effect in normal and high speed reproduction. 
At this point, TD shows a track deviation degree of the head. If TD=1, the 
center of the head is in accord with that of the track and thus tracking 
is completely performed. If TD&lt;1, the track is deviating from the head. 
That is, in variable speed play, the head passes through many tracks so 
that the region in which a head can read information data for one track 
should be within the range of 0.ltoreq.TD.ltoreq.1. 
Inter-segment interleaver 40 performs inter-segment interleaving and 
provides the interleaved data to outer encoder 50, where the inter-segment 
interleaving can be achieved by interleaving data between segments in the 
process of reading out data from memory mapper 20 in the unit of segment. 
Outer encoder 50 performs outer encoding with respect to the data from 
inter-segment interleaver 40 and provides the encoded data to 
intra-segment interleaver 60. Intra-segment interleaver 60 performs 
intra-segment interleaving, i.e., interleaves data inside of segments as 
shown in FIG. 5C. Thus, burst errors in the data stream can be replaced by 
random errors and the data from intra-segment interleaver 60 are 
ECC-processed by inner encoder 70 and then written to the tape through the 
head. 
Referring to FIG. 6, the interleaving/deinterleaving apparatus for a 
digital VCR according to another embodiment of the invention comprises a 
formatter 100 for performing the recording format with respect to an input 
digital data stream in accordance with an ID information and an overhead 
information, a memory mapper and decoder 200 for keeping the continuity 
between the segments and performing interleaving with respect to the 
output of formatter 10 in accordance with the characteristics of the VCR 
and dividing the data stream, buffering section 300 for buffering the 
outputs from memory mapper and decoder 200, delay section 400 for 
successively delaying the data buffered from buffering section 300 for a 
predetermined time, encoder 500 for encoding the data delayed by delay 
section 400, inter-symbol interleaver 600 for performing inter-symbol 
interleaving with respect to the output of encoder 500, inner encoder 700 
for performing inner encoding with respect to the interleaved data from 
inter-symbol interleaver 600, channel coder 800 for connecting the data 
stream to tape channel, and channel decoder 900 for decoding the data 
reproduced from the tape. 
In the above embodiment, formatter 100 receives a digital data stream and 
performs VCR recording format with respect to the respective data segment 
lines (compressed data or error correction (E.C.C.)) except for the 
preceding header portion as shown in FIG. 7A and then provides the 
formatted data stream to memory mapper and decoder 200. Memory mapper and 
decoder 200 performs interleaving with respect to the provided data stream 
in accordance with the characteristics of the VCR, keeping the continuity 
between the segments. The interleaved data pass through respective buffers 
B1 to Bn in buffering section 300 and respective delays D1, to Dn in delay 
section 400 and then are constructed as shown in FIG. 7B. 
When the interleaved data are encoded through encoder 500 and applied to 
inter-symbol interleaver 600, the data are shuffled completely as shown in 
FIG. 7C and are inner-encoded by inner encoder 700 so as to be provided to 
channel coder 800. Channel coder 800 records the data provided from inner 
encoder 700 to the tape by connecting the channel of the data stream to 
that of the tape, thereby completing the interleaving process. 
When the data recorded on the tape are made to be reproduced, channel 
decoder 900 decodes the reproduced data and detects and corrects the 
errors. Thereafter, the detected data are performed by the aforementioned 
interleaving process reversely, i.e., performed by deinterleaving process. 
In variable speed reproduction play, the interleaving region is determined 
in accordance with the predetermined maximum speed. The segments in the 
neighboring areas within the determined region are successively formatted 
as shown in FIG. 7A, 7B and 7C. Accordingly, discontinuity between 
segments does not occur and thus the interleaving effect is not reduced at 
any speed lower than maximum speed though the head of VCR may have 
nonlinear traces. 
FIG. 8 shows still another embodiment of the interleaving apparatus 
according to the present invention. The apparatus comprises format divider 
101 for dividing an input compressed data stream into a synchronizing 
signal and data and formatting the divided synchronizing signal and data, 
memory mapper 102 for reading and storing data segments of the divided 
data in zigzag form, outer coder 103 for performing outer coding (i.e., 
Reed-Solomon coding) with respect to the data N1 and K1 stored in memory 
mapper 102 and providing the data to which an outer code symbol is added, 
demultiplexer 104 for demultiplexing the segments provided from outer 
coder 103 and temporarily storing the data segments in n buffers 105 
arranged in a vertical direction, multiplexer 106 for multiplexing the 
data segments from buffers 105 so as to provide the multiplexed data, 
inner coder 107 for performing inner coding with respect to the data from 
multiplexer 106 and providing data having an inner code symbol added 
thereto, inter-symbol interleaver 108 for performing inter-symbol 
interleaving with respect to the data provided from inner encoder 107, 
synchronizing and header signal generator 110 for receiving the 
synchronizing signal from format divider 101 and providing a header signal 
corresponding to the synchronizing signal along with the synchronizing 
signal, system controller 109 for controlling format divider 101 and 
synchronizing and header signal generator 110 in accordance with an input 
TBM signal, formatter 111 for formatting the synchronizing and the header 
signals form synchronizing and header signal generator 110 and the symbol 
code data from inter-symbol interleaver 108, channel modulator 112 for 
modulazing the data from formatter 111 and providing the modulated signal 
as a tape recording signal, and recording amplifier 113 for amplifying the 
data from channel modulator 112 to make the data have an appropriate level 
and recording the amplified data to the tape. 
For the reproduced data, the deinterleaving process is performed by the 
deinterleaving apparatus in which the above interleaving apparatus is 
reversely constructed as shown in FIG. 9 and the description thereof will 
be omitted. 
Meanwhile, it will be understood that the data divided by format divider 
101 enter in two directions so as to be divided into two channels and the 
description for only one channel will follow. 
Format divider 101 receives a compressed data stream and divides the data 
stream into a synchronizing signal and compressed data as shogun in FIG. 
11A and then performs formatting. The divided data are scanned in zigzag 
form and stored in the unit of segment in memory mapper 102 as shown in 
FIG. 11B, being divided in to A channel data and B channel data as shown 
in FIG. 11C so as to be separately processed when the data is read out 
therefrom. 
Multiplexers 106 and 126 multiplex the interleaved data and provide the 
multiplexed data. Inner encoder 107 and 127 add the Reed-Solomon code of 
(N.sub.2, K.sub.2) to the data provided from multiplexers 106 and 126 and 
perform inner encoding as shown in FIG. 11G so as to provide the encoded 
data to inter-symbol interleavers 108 and 128. Inter-symbol interleavers 
108 and 128 perform inter-symbol interleaving with respect to the symbol 
data, thereby correcting the random errors. 
Thus, from synchronizing and header signal generator 110, formatters 111 
and 131 receive a synchronizing signal divided form format divider 101 and 
a header signal corresponding to the synchronizing signal under the 
control of system controller 109 and perform formatting with respect to 
the received data along with the data from inter-symbol interleavers 108 
and 128 as shown in FIG. 11H so as to provide the formatted data to 
channel modulators 112 and 132. Channel modulators 112 and 132 perform 
channel modulation with respect to the provided data. The modulated data 
enter recording amplifiers 113 and 133 to be amplified and then are 
recorded on the tape. 
In reproduction, errors can be prevented by reversely reproducing the data 
formatted and recorded as described above by way of the circuit of FIG. 9. 
FIG. 13 shows still another embodiment of the interleaving apparatus 
according to the present invention. The apparatus comprises a format 
divider 101 for dividing an input compressed data stream into a 
synchronizing signal and data and formatting the divided synchronizing 
signal and the data, memory mapper 102 for reading out and storing in 
zigzag form the data divided by format divider 101, demultiplexer 104 for 
dividing the data in a segment stored in memory mapper 102 into n blocks 
and demultiplexing each segment block and storing the demultiplexed data 
segment in n buffers 105, multiplexer 106 for multiplexing the data 
temporarily stored in buffer 105, inter-symbol interleaver 108 for 
performing interleaving with respect to the symbol data multiplexed 
through multiplexer 106 in order to divide the symbol data along the same 
line per block, synchronizing and header signal generator 110 for 
receiving the synchronizing signal from format divider 101 and providing a 
header signal corresponding to the synchronizing signal along with the 
synchronizing signal, a system controller 109 for controlling format 
divider 104 and synchronizing and header signal generator 110 in 
accordance with an input TBM signal, formatter 111 for formatting the 
synchronizing and the header signals from synchronizing and header signal 
generator 110 and the symbol data from inter-symbol interleaver 108, 
channel modulator 112 for modulating the data from formatter 111 so as to 
make the modulated data suitable for recording on the tape, and recording 
amplifier 113 for amplifying the data from channel modulator 112 up to an 
appropriate level and recording the amplified data to the tape. 
It will be understood that the data divided by format divider 101 enter in 
two directions so as to divide the data into two channels and the 
description for only one channel will follow. 
In addition, the deinterleaving apparatus corresponding to the interleaving 
apparatus is as shown in FIG. 14 and the construction and operation 
thereof are simply the reverse of the interleaving apparatus and thus will 
be omitted. 
Format divider 101 divides an input compressed data stream into a 
synchronizing signal and compressed data and performs formatting as shown 
in FIG. 18 and thus arranges the compressed data successively per line 
(i.e., 1 segment). The data of the divided synchronizing signal and data 
are successively written in memory mapper 102 in zigzag form in the unit 
of segment as shown in FIG. 17A. 
Demultiplexer 104 performs demultiplexing with respect to the data stored 
in memory mapper 102 so as to divide one segment into N blocks as shown in 
FIG. 7B and writes respective segments for each block to buffer section 
105 including N buffers. That is, one segment is written to buffer 1 and 
the next segment is being shifted for one vertical size so as to be 
written to buffer 2 as shown in FIG. 17C. 
Multiplexer 106 performs multiplexing with respect to the vertically 
written data and then transmits to inter-symbol interleaver 108 symbols 
for blocks in the respective segments. Inter-symbol interleaver 108 
performs interleaving to form n blocks by grouping the data in the same 
position as shown in FIG. 17D, i.e., classifies the data in accordance 
with line. The interleaving process to classify the data is as shown in 
FIG. 19A, while the conventional process is as shown in FIG. 20A. 
Thus, from synchronizing and header signal generator 110, formatter 111 
receives a synchronizing signal divided from format divider 101 and a 
header signal corresponding to the synchronizing signal under the control 
of system controller 109 and performs formatting with respect to the 
received data along with the data from inter-symbol interleaver 108 as 
shown in FIG. 17E, so as to provide the formatted data to channel 
modulator 112. Channel modulator 112 performs channel modulation with 
respect to the provided data. The modulated data enter recording 
amplifiers 113 to be amplified and then are recorded on the tape. 
In the conventional method, after the deinterleaving process is completed 
by performing interleaving in opposite by way of the apparatus of FIG. 14, 
the incomplete segment should be removed as shown in FIG. 20B. However, 
according to the present invention, as shown in FIG. 19B, the incomplete 
segment becomes longer and the orders of data between neighboring segments 
are changed, thereby connecting the blocks between incomplete segments and 
increasing the probability of including a slice lying in two segments. 
Accordingly, the slices extracted from segments can be detected still 
better, thereby improving the picture quality. 
The process of extracting slices from incomplete segments to make them 
useful will be explained with reference to FIG. 21. 
First, after interleaving/deinterleaving is performed, it is detected 
whether a recorded/reproduced data segment is complete or incomplete. If 
the detected data segment is complete, normal data processing is performed 
with respect to the complete data segment and ends up when the last data 
segment is processed. If the detected data segment is incomplete, a 
segment header signal and the end point DSEP and the start point DSSP of 
the incomplete data are detected. 
If the start point of the data stream does not exist, the size of the start 
point of a slice a is compared with that of the end point of the data 
stream. At this point, if the start point of the slice has a smaller size, 
a suitable process is performed and ends up when the last segment data is 
processed. If the size of the start point of the slice is not smaller, it 
is detected whether the data segment is the last one and the process ends 
up at that point, which means that no slice is taken. 
Meanwhile, if the start point of the incomplete data stream exists, the 
size of the start point of the slice is compared with that of the data 
stream. At this time, if the size of the start point of the slice is 
bigger, a corresponding process is performed until the last data segment 
is processed. When the last data segment comes out, the process ends up 
and the start point of the slice which is not bigger will be removed. As a 
result, the slice extracted from the incomplete data segment can be used 
for improved picture quality. 
From the foregoing, it will be apparent that according to the present 
invention, an interleaving/deinterleaving is performed within an 
interleaving region which is restricted in accordance with a predetermined 
maximum speed in variable speed play, so that error correction capability 
is improved though the VCR head may have a nonlinear trace. Error 
correction capability may also be improved when the error decoding array 
has insufficient data in high speed play. Furthermore, many slices can 
enter an incomplete data segment easily, thereby providing picture quality 
of high resolution. 
Whereas the present invention has been described in particular relation to 
the drawings attached hereto, it should be understood that other and 
further modifications, apart from those shown or suggested herein, may be 
made with in the spirit and scope of this invention.