Improvement For CBC Algorithm And Research On CBR Mode For AV3

AVS is the second generation source coding standard which is developed by Chinese experts independently, it includes four main technical standards: system, video, audio and digital copyright management, and supporting standard: consistency test. AVS audio is the third part of AVS standard, with the advantages of high compression ratio, high quality and fine grain scalability coding, and is applied in the field of significant information industry. AVS is the only standard that supported by government and has the advantage of very low patent fee compared with MPEG-2. Both of these two advantages indicate that AVS will have good prospects, so it is significant of making research on AVS audio.In this paper, AV3's core algorithm-CBC is analyzed specially and a new method for the CBC is proposed which is more suitable in low bit-rate. By the analyzing of MATLAB, the results indicated that the error in the improved CBC has decreased about 6.52dB when their bitrate is comparative and bitstream is truncated in formatting.When channels' wideband is limited, it is more suitable of using CBR mode than ABR, so the paper also studies about CBR mode for AV3. The key technical of perceptive codec is first analyzed, and then the quantization of AV3 codec is analyzed particularly, which is similar to AAC and MP3. But because there are some shortcomings in the double-loop iteration, so the improved double-loop iteration is applied. The paper also programs its C codes based on Windows and analyzes its decompression files, which indicates that: the CBR mode codec is more convenient than ABR mode on the controlling of bitrate, when channels' wideband is limited, the bitstream of CBR mode will not be truncated and when their bitrate is comparative, the CBR mode codec consists more spectral than ABR, but when the context is complex or changes sharply, CBR mode codec may produce more errors.