Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-11-19
2002-09-10
Le, V. (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240260, C386S349000, C348S441000
Reexamination Certificate
active
06449310
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video signal coding apparatus for coding a video signal.
2. Description of the Related Art
In recent years, techniques for compressing digital video signals have been developed. A huge amount of funds and labor, however, are required to standardize a compression method and to implement a compression algorithm in hardware (LSI), so attempts are being made to make minor changes in a compression algorithm that has been implemented in hardware using existing standards and commercially available video equipment in order to develop a new video signal coding apparatus.
FIG. 5
describes a conventional video signal coding apparatus that codes a 4:2:2 sampling signal using equipment for coding 4:1:1 sampling. The equipment for coding 4:1:1 sampling corresponds to a compression algorithm that has been implemented in hardware using existing standards and commercially available video equipment.
In
FIG. 5
,
501
is a video signal input terminal that inputs a digital video signal,
502
is an effective-area blocking. device for dividing only the effective area of the input signal into blocks and outputting the blocks to two channels, and
503
and
504
are effective-area encoders that hight-efficiency-codes the blocks in the effective area that have been input. The effective area is simply described. If the digital video signal is transmitted based on, for example, a 525/60 system, all the areas of the video signals within the transmitted signal is composed of 480 main lines and 3 or 7.5 accompanying lines. Herein, the 480 lines are referred to as an effective area and the accompanying lines are referred to as an additional area. Conventional video signal coding apparatuses process only the video signals in the effective area. If the digital video signal is transmitted based on, for example, a 625/50 system, all the areas of the video signals within the transmitted signal is composed of 576 main lines and 9 accompanying lines.
The operation of the conventional video signal encoder of this configuration is described.
A digital video signal with 4:2:2 sampling is input from the input terminal
501
. The effective-area blocking device
502
divides only the effective area within the input signal into macro blocks.
During 4:1:1 signal sampling, the macro blocks are composed of four DCT (Discrete Cosine Transform) blocks for a luminance signal that are arranged continuously on a screen in the horizontal direction, and two DCT blocks for color difference signals that are arranged at the same positions of the screen as the four DCT blocks for a luminance signal. During 4:2:2 signal sampling, the macro blocks are composed of two DCT blocks for a luminance signal that are arranged continuously on the screen in the horizontal direction, and two DCT blocks for color difference signals that are arranged at the same positions of the screen as the two DCT blocks for a luminance signal.
Thus, since the number of macro-blocks per frame in a 4:2:2 signal is double that in a 4:1:1 signal, an effective-area encoder that can deal with 4:1:1 signals is adapted for two channels as shown in FIG.
5
.
As described above, however, the number of DCT blocks within a single micro block is different between a 4:1:1 signal and a 4:2:2 signal, so the effective-area encoders
503
and
504
for 4:1:1 signals cannot be directly used. Thus, the effective-area blocking device
502
adds to the 4:2:2 signal, two DCT blocks consisting of dummy data so that the number of DCT blocks in a single macro block in the 4:2:2 signal is the same as that in the 4:1:1 signal, thereby enabling the use of the effective-area encoders
503
and
504
for 4:1:1 signals.
Thus, the effective-area blocking device
502
divides one-frame data into macro blocks including dummy DCT blocks in which all pixel values are the same, further divides the macro blocks for a single frame into two channels, and output the macro blocks to the effective-area encoders
503
and
504
. As in the input of the 4:1:1 signal, the effective-area encoders
503
and
504
code the output from the effective-area blocking device
502
.
FIG. 6
shows a list of data obtained by applying the same coding to the macro blocks of the 4:2:2 signal as in the 4:1:1 signal.
As shown in
FIG. 6
, coding the 4:2:2 signal essentially uses an area to which are input AC components stored in four areas(e.i. areas 0, 2, 4, and 5) out of the six areas 0 to 5 to which data obtained by coding the 4:1:1 signal is input, and an area to which are input AC components stored in the areas 1 and 3 in which the dummy DCT blocks are recorded.
Since, however, the dummy DCT blocks whose all the data in the DCT blocks has the same pixel value, coding with the DCT blocks provides only DC values and no AC components. Consequently, data obtained by applying VLC (Variable Length Coding) to DCT data consists of only DC components and an EOB that is a coding end code. Thus, in
FIG. 6
, although 9 DC bits, 3 additional-information bits, and 4 AC bits are normally input to reserved areas
601
and
602
, 9 DC bits from the dummy DCT blocks, 3 additional-information bits, and 4 coding end code (EOB) bits are input to these areas if the 4:2:2 signal is dealt with.
The area in which the AC components in the areas 1 and 2 are to be housed is used to record therein AC component data that cannot be stored in the other areas.
BRIEF SUMMARY OF THE INVENTION
Object of the Invention
According to the above method, however, DC values and additional information for the dummy DCT blocks generated during the coding of the 4:2:2 signal are not required to decode a video signal from coded data, so the coded data includes useless data and cannot be efficiently used.
In view of this conventional problem, this invention provides a video signal coding apparatus that can use coded data more efficiently and that can improve the error immunity.
SUMMARY OF THE INVENTION
A first invention of the present invention is a video signal coding apparatus which comprises:
division means for dividing an input digital video signal into a first and a second areas;
first blocking means for dividing said first area into the units of first blocks;
first compression means for hight-efficiency-coding said first block to create a first compressed block;
second compression means for hight-efficiency-coding said second area to create second compressed data;
second blocking means for dividing said second compressed data into the units of second compressed blocks each including a luminance signal for a plurality of pixels and at least one color difference signal for pixels arranged at the same position as the plurality of pixels on a screen; and
substitution means for substituting said second compressed block for data stored in the same first compressed block at a predetermined position.
This configuration, for example, allows all coded data to be used effectively and inputs to the same block, luminance and color difference signals for a plurality of pixels located at the same position on a screen. Consequently, even if an error occurs, it affects only the plurality of the pixels compared to more pixels in the prior art, thereby substantially improving the error immunity to reduce the adverse effects on image quality during decoding.
A second invention of the present invention is a video signal coding apparatus which comprises:
division means for dividing an input digital video signal into a first and a second areas;
first blocking means for dividing said first area into a plurality of first blocks and dividing the plurality of said first blocks into x (x≧2) channels for output;
first compression means for hight-efficiency-coding said first block to create a first compressed block;
second compression means for hight-efficiency-coding said second area to create second compressed data;
second blocking means for dividing said second compressed data into the units of second compressed blocks including a luminance signal for a plurality of pixels and at least one col
Fujiwara Yuji
Nishino Masakazu
Takeuchi Seiichi
Wake Kazuhiro
Le V.
Matsushita Electric - Industrial Co., Ltd.
Smith , Gambrell & Russell, LLP
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