Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1999-01-25
2002-02-19
Rao, Andy (Department: 2713)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C375S240020, C375S240030
Reexamination Certificate
active
06348945
ABSTRACT:
TECHNICAL FIELD
This invention relates to a data encoding method and a data encoding apparatus for carrying out compression-encoding of digital information data such as digital video signal, etc., and more particularly to a data encoding method and a data encoding apparatus capable of easily changing compression factor in the data compression format of fixed compression factor.
BACKGROUND ART
Since data quantity of digital information data such as digital video signal, etc. is vast, there are many instances where compression encoding for compressing data quantity is implemented. Data encoding methods and data encoding apparatuses particularly using DCT (Discrete Cosine Transform) of this compression encoding are frequently used in recent years. For example, also in the format of digital VTR having tape width of ¼ inches, which is the so-called DV format, the data encoding method using this DCT is employed.
In such an encoding of digital information data, the compression factor and the data rate are fixed in order to carry out transmission and/or recording/reproduction by a predetermined format. For example, in the case where synchronization is taken in fixed block units, data compression is implemented within the range where data quantity is not above the maximum data quantity every block. Invalid data are filled into the portions except for compressed valid data within respective blocks so that respective data quantities every blocks are fixed. Moreover, it is also conceivable to allocate data over blocks. In the case where compressed valid data quantity corresponding to a predetermined block is above the maximum data quantity within the corresponding block, overflowed valid data is allocated to any other block where valid data quantity is less. For example, in the above-described DV format, allocation of data between respective macro blocks is carried out within video segments of fixed length consisting of five macro blocks obtained after undergone shuffling within picture on screen.
Meanwhile, in recent years, the data recording capacity of the hard disc has been increased and it is also put into practical use to record or reproduce compressed data of digital video signal, etc. with respect to the hard disc. Since recording/reproducing apparatus (unit) using such hard disc, etc. is random-accessible, it is possible to momentarily retrieve an arbitrary image. This recording/reproducing unit is suitable in, e.g., editing work.
In this case, e.g., in use purpose of carrying out off-line editing of video signals, it is sufficient to take picture quality to such a degree that the content can be confirmed. It is important to increase the compression factor to reduce data quantity in a sense of saving the capacity of the recording medium. On the contrary, in the main editing, it is important to hold the compression factor down to lower value to realize improvement of the picture quality. In addition, if the compression factor can be changed in dependency upon use purpose, it is possible to realize the picture qualities and the medium capacities optimum for respective use purposes. This is preferable.
This invention has been made in view of actual circumstances as described above, and its object is to provide a data encoding method and a data encoding apparatus which are capable of easily changing the compression factor in the format of digital VTR having tape width of ¼ inches, which is data compression format of the fixed compression factor like the so-called DV format.
DISCLOSURE OF THE INVENTION
A data encoding method and a data encoding apparatus according to this invention are adapted so that in the case where input data is orthogonally transformed to quantize the input data thus transformed thereafter to allow the quantized data to undergo variable length encoding, an approach is employed to estimate total quantity of encoded data when undergone variable length encoding on the basis of the orthogonally transformed data to determine quantization step in quantization on the basis of reference value different (changing) in dependency upon compression factor and the estimated data quantity.
By changing the reference value in dependency upon the compression factor, total quantity of encoded data is changed.
Moreover, a data encoding method and a data encoding apparatus according to this invention are adapted so that in the case where input data is orthogonally transformed to quantize the data thus transformed thereafter to allow the quantized data to undergo variable length encoding, an approach is employed to change threshold value for designating class indicating fineness of quantization on the basis of the orthogonally transformed data in dependency upon the compression factor.
By changing threshold value of class designation in dependency upon the compression factor, total quantity of encoded data is changed.
In this case, when there is assumed picture compression format of the fixed compression factor such that the input data is picture data, and that in quantizing DCT coefficient data obtained by carrying out Discrete Cosine Transform (DCT) at any one of plural quantizers to allow the quantized data to undergo variable length encoding, an approach is employed to estimate data quantity when quantization and variable length encoding in video segment units of DCT coefficient data to compare the estimated data quantity with reference value to thereby determine optimum quantizer to compare data of block unit of DCT coefficient data with threshold value to thereby determine class indicating fineness of quantization, it is preferable to change the reference value, or reference value and threshold value in dependency upon information of a desired compression factor.
By changing the reference value, or the reference value and the threshold value in dependency upon information of the compression factor, finally encoded data quantity obtained after undergone compression-encoding is changed. Thus, the comparison factor can be changed.
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Bolito Bruno
Frommer William S.
Frommer & Lawrence & Haug LLP
Rao Andy
Sony Corporation
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