Image analysis – Image compression or coding – Adaptive coding
Reexamination Certificate
2000-06-22
2004-01-27
Couso, Jose L. (Department: 2621)
Image analysis
Image compression or coding
Adaptive coding
Reexamination Certificate
active
06683989
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a coding apparatus for generating the secondary-coded bit streams by recoding the primary-coded bit streams of the previously compressed-coded video signal, for example, to reduce an amount of data. More particularly, the present invention relates to a coding apparatus capable of generating the secondary-coded bit streams, in which the influence of the code amount controlling unit for the primary-coded bit streams can be suppressed and which have uniform picture quality, by calculating an image complexity using the code amount and the quantization coefficients of the primary-coded bit streams every block, then setting a target code amount every block based on the value, and then recoding the bit streams to mate with the target code amount.
2. Description of the Related Art
In the prior art, if image information are transmitted/stored in the digital image process system or the digital image service system, an amount of information can be reduced by coding the image information and then the coded bit streams whose amount of information are reduced are transmitted/stored.
Meanwhile, in recent years, the applications have been increased which generate the secondary-coded bit streams by decoding the image information from the primary-coded bit streams, in which the image are compressed-coded previously, and recoding such image information under different coding conditions with the higher compression ratio, etc., and then transmit/store such secondary-coded bit streams.
For example, in the case where the image information are broadcasted, the cascade transmission of the digital signal, i.e., hierarchical transmission to process one image in plural times is now carried out while executing the edit processes such as collection of image material, primary distribution between the TV stations, secondary distribution to homes, etc. It is expected that, as a variety of broadcasting modes are going to be utilized, the transmission system that differs from the hierarchical transmission and has higher degree of freedom will be spread.
Also, it is expected that, as for the video clip which are stored in the image database, etc. and are expected to be utilized as the library, video sources are provided from many users and utilized by many users at the same time, and also are transmitted/stored again and again while executing the edit of them.
In this manner, the conventional cascade-connected coding system for performing the coding and the decoding in many times is constructed by cascade-connecting the units for performing the coding and the decoding only once as they are to execute the recoding. Hence, upon recoding, the coding using parameters peculiar to the recoding apparatuses is also performed, and thus the coding history of the object image is not considered at all. That is, for example, in the prior art, the processes that take account of only the compression ratio, etc. of the recoding apparatus have been performed upon recoding.
Also, as another example of the recoding application, reproducing/recording on the digital VDR (Video Disc Recorder) may be considered. In the case of this example of the application, the video streams are broadcasted to the user's home at a certain broadcasting quality (e.g. , quality which corresponds to a bit rate of 6 Mbps for the standard definition video such as “almost NTSC” or 24 Mbps for the high-definition video such as “almost Hi-vision”). In other words, when receiving these video streams, the user records the video data at a high coding rate, which is similar to the extended reproducing EP mode (long time mode) of the existing home video tape recorder, e.g., the VHS recorder, by using the recoding function of the digital VDR, and thus a number of video programs of low quality are recorded in the digital VDR.
However, only information of higher quality among original signals must be actively employed as much as possible upon recoding. Thus, the picture quality of new signals obtained at a lower bit rate is also requested to have the quality as high as possible. More particularly, in the unit which repeats the coding and the decoding in plural times, preferably the picture quality of the signals obtained by repeating the coding and the decoding in plural times should be set close to the picture quality of the signals which are generated by coding the original video source at a reduced rate only once, for example, as much as possible.
A schematic configuration of the recoding apparatus in the prior art, which generate the secondary-coded bit streams by decoding the primary-coded bit streams being coded previously and then recoding them so as to reduce an amount of data, is shown in FIG.
1
.
In this example in
FIG. 1
, merely major functional elements are illustrated to show a general operation of the recoding apparatus. For example, various type data are contained in the compressed video signal, and only a part of these data are quantized. Other data are caused to detour the requantizing or recoding unit and then multiplexed again with the recoded data in the multiplexer
106
. Since it is publicly known generally that the multiplexer
106
is needed to execute the above function and the multiplexing function of the multiplexer
106
is also publicly known, their explanation will be omitted in this disclosure.
In
FIG. 1
, the primary-coded bit streams that have already been compressed or coded are input into the coded video input terminal
100
. That is, these primary-coded bit streams correspond to the signals that are to be recoded in the recoding apparatus shown in FIG.
1
.
Here, assume that the primary-coded bit streams to be recoded are the block-coded signals. That is, respective images are divided into a plurality of blocks or macroblocks prior to the coding and then compressed by the predetermined compressing and coding approach every block or macroblock. Therefore, the streams of blocks or macroblocks that are coded at least partially as above are supplied to the coded video input terminal
100
. Also, assume that at least a part of the data in respective macroblocks are quantized and are variable-length-coded. As the representative example of the above compressed coding approach, so-called MPEG (Moving Picture Experts Group) 1 system, MPEG 2 system, etc. may be listed.
The above-mentioned primary-coded bit streams being input into the coded video input terminal
100
are then supplied to the variable-length decoder (VLD)
101
that executes the variable-length decoding. In the example in
FIG. 1
, such a configuration is illustrated that motion vectors contained in the bit streams and other code words which are not quantized are not supplied to the circuits in the succeeding stage (the inverse-quantizing unit (Q
−1
)
103
, the quantizing unit (Q)
104
, and the variable-length coding unit (VLC)
105
) so as to detour them. However, for example, if these units in the succeeding stage (the inverse-quantizing unit
103
, the quantizing unit
104
, and the variable-length coding unit
105
) can be conditioned not to react with signal components which are not. to be changed according to the recoding apparatus, actually these motion vectors and other code words which are not quantized may be set to pass through these units in the succeeding stage (the inverse-quantizing unit
103
, the quantizing unit
104
, and the variable-length coding unit
105
). The code words that are variable-length-decoded by the variable-length decoding unit
101
are delayed by the delay unit
102
by a predetermined time, and then supplied to the inverse-quantizing unit
103
.
The inverse-quantizing unit
103
reconstructs the signal components, which are quantized in the compression process, by inverse-quantizing the code words that are subjected to the variable-length decoding. The signal components which are inverse-quantized by the inverse-quantizing unit
103
are then supplied to the quantizing unit
104
.
The quantizing unit
104
quantizes (requant
Fujiwara Mitsuaki
Morita Kazuhiko
Sugahara Takayuki
Berkowitz Marvin C.
Couso Jose L.
Nath Gary M.
Nath & Associates PLLC
Victor Company of Japan , Limited
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