Sanyo Electric Co., Ltd.

Koichi Tsuchikane

Takashi Urano

Yasuhachi Hamamoto

Satoko Kobayashi

Yasunori Tsuji

A decoding start controller is capable of appropriately decoding pictures up to the final picture, even if the amount of the data stored in a bit-stream buffer is reduced, as a result of partial storage of the data in an internal local buffer. Further, the decoding start controller is capable of decoding extremely short bit-stream data. If completion information, which is sent from an input side of the bit-stream data and represents completion of input of the bit-stream data, is detected, a decoding start instruction signal is output to a variable-length decoder regardless of a value of VBV occupancy. In short, when the amount of the data stored in the bit-stream buffer connected to the decoder having the decoding start controller, is equal or greater than the value of VBV occupancy, the decoding start instruction signal will usually be sent to the variable-length decoder: namely, so-called decoding start control operation based on value of VBV occupancy. If the completion information is detected, the decoding start control operation based on the value of VBV occupancy is interrupted, and the decoding start instruction signal is output.

Decoding start controller, decoder, and decoding system

An input bitstream (a first bitstream) is divided into a main code having a changeable length and the remaining data. The main code is subjected to a bit-rate conversion and combined with the remainig data to output a second bitstream. By this arrangement, the configuration ofthe bit-rate conversion circuit can be simplified and delay in the conversion process can be reduced. Incidentally, the main code corresponds to the DCT-coefficient data(e) and the quantizer scale(d), while the remaining data corresponds to the header data(a), the handling type data(b) and the motion vector data(c) respectively. Furthermore, by using the fact that if the quantizer scale is enlarged and the compression rate is raised, the degradation of a reproduced picture with a large DCT-coefficient's value of higher frequency terms is not conspicuous but the degradation of a reproduced picture with a small DCT-coefficient's value of higher frequency terms is conspicuous, and by changing the compression rate based on the DCT-coefficient's value of higher frequency terms, a bitstream with a low bit-rate but a small degradation in the reproduced picture quality can be obtained.

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Tokyo, Japan

Koichi Tsuchikane