Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1997-11-28
2002-05-14
Garber, Wendy R. (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C348S700000, C375S240030
Reexamination Certificate
active
06389224
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an audio and/or video data coding and recording apparatus for variable length coding noncompressed audio and/or video data by a compressing and coding system such as the MPEG (Moving Picture coding Experts Group) method and recording the same on a conventionally existing recording medium such as a magneto-optical disk (MO) and hard disk (HD) or a new recording medium such as a digital video disk (DVD).
BACKGROUND ART
When reading out source data (stock data) from a recording medium of a video tape (master video tape) on which program data and other uncompressed and uncoded original audio and/or video data (source data or stock data) have been recorded for the purpose of compression and coding, usually, to prepare against unforeseen situations, the practice has been to reproduce the source data from a master video tape, copy it onto another VTR tape (work video tape), and further reproduce the source data from the work video tape for compression and coding.
Further, as the compression and coding system used when compressing and coding audio and/or video data and recording the same on a recording medium such as a magneto-optical disk (MO) or a digital video disk (DVD) or transmitting the same to another apparatus, a fixed rate (fixed length) compression and coding system and a variable rate (variable length) compression and coding system have been known.
Below, an explanation will be made of the variable rate compression and coding system and the fixed rate compression and coding system by taking as an example a case of compressing and coding video data. Note that, the compression and coding of audio data can be considered basically similar to the compression and coding of video data, but audio data generally consists of a smaller amount of data than video data and can be more easily compressed and coded than video data, therefore the compression and coding of the audio data will not be referred to here.
In the fixed rate compression and coding system, the compression and coding rate (bit rate) is always constant.
On the other hand, in the variable rate compression and coding system, in order to maintain the quality of the picture as a whole when expanding and decoding the compressed and coded data (compressed data), the compression and coding rate is changed based on the complexity of the picture and motion. For example, if variable rate compression and coding are performed on a relatively difficult part where the motion of the source data is vigorous, the amount of generated data becomes larger (bit rate becomes higher), while if the variable rate compression and coding is performed on a relatively simple part where the motion of the source data is small, the amount of generated data becomes smaller (bit rate becomes lower).
When considering the quality of the video after the expansion and decoding, when using the variable rate compression and coding system, it is possible to allocate a larger amount of data for the compression and coding of a complex picture and allocate a smaller amount of data for the compression and coding of a simple picture, therefore the compression and coding can be carried out while maintaining a uniform picture for the picture as a whole.
When performing the compression and coding by the fixed rate compression and coding system, however, at a part where the picture is complex and the motion is vigorous (picture pattern is complex) and therefore the amount of information is large, the fixed amount of data allocated to that part is not enough to maintain a sufficient quality of the picture. Conversely, in a part where the picture is simple and the motion is mild (picture pattern is simple) and therefore the amount of information is small, the fixed amount of data becomes excessive with respect to the amount required for maintaining a sufficient quality of the picture.
Accordingly, in general, the quality of the picture after the expansion and decoding becomes higher in the case where the variable rate compression and coding system is used in comparison with the case where the fixed rate compression and coding system is used.
When considering the amount of the data after compression, when using the fixed rate compression and coding system, since the source data is compressed and coded by a constant compression and coding rate, the amount of data after compression and coding can be correctly estimated from the amount of the source data before the compression and coding. Accordingly, the recording medium having the recording capacity necessary for recording the data after compression and coding can be easily selected.
On the other hand, as mentioned above, if the fixed rate compression and coding system is used, since the compression and coding are carried out with the same compression and coding rate both for a part where the pattern of the source data is complex and for a part where the pattern is simple, the quality of the picture at the part where the pattern of the source data is complex becomes poor.
Further, in the fixed rate compression and coding system, since the amount of data after the compression and coding changes in accordance with the value of the compression and coding rate, when the storage capacity of the recording medium for recording the compressed data is small, the compression and coding rate must be lowered and thus the quality of the overall picture after expansion and decoding becomes low. Accordingly, in order to maintain a high quality of the picture after the expansion and decoding, the recording capacity of the recording medium must be made large.
When using the variable rate compression and coding system, the compression and coding are carried out while adaptively changing the compression and coding rate in accordance with the complexity of the pattern. That is, in the variable rate compression and coding system, the part where the pattern of the source data is difficult is compressed and coded with a low compression and coding rate, while the video data of the part where the pattern is simple is compressed and coded with the high compression and coding rate.
Accordingly, if the variable rate compression and coding system is used, the quality of the picture after the expansion and decoding can be improved in comparison with the case where the fixed rate compression and coding system is used.
When the variable rate compression and coding system is used, however, the amount of data after the compression and coding cannot be estimated definitively from the amount of the source data before the compression. Accordingly, with just a single compression and coding processing, the source data cannot be reliably compressed and coded to an amount of data less than the recording capacity of a DVD (digital video disc device) or other recording medium and reliably recorded on the same.
The fixed rate compression and coding system and the variable rate compression and coding system have their advantages and disadvantages as mentioned above, but a recent trend has been for the greater use of the variable rate compression and coding system, which gives a higher quality of the picture as a whole after the expansion and decoding, in comparison with the fixed rate compression and coding system. As representative variable rate compression and coding systems, the MPEG system (system of compression and coding of moving pictures developed by the Moving Picture Coding Experts Group) as represented by MPEG
1
and MPEG
2
have been known.
In order to record compressed data on a DVD or other recording medium, it is necessary to properly set the compression and coding rate (bit rate) and to compress and code the data and record the compressed data so that the compressed data can be accommodated in the recording medium. For this reason, a two-path system mentioned below is applied.
First, compression and coding process is carried out for determining the compression and coding rate so that the amount of the data after the compression and coding becomes less than the recording capacity of the DVD or other r
Imahashi Kazuyasu
Mori Kenji
Setogawa Toshiaki
Tanaka Kentaro
Yamauchi Hiroyuki
Frommer William S.
Frommer & Lawrence & Haug LLP
Garber Wendy R.
Onuaku Christopher
Polito Bruno
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