Design On The Programmable Divider And Research On The Transcoding Of MPEG Audio Bit-Stream

At present,the MPEG-2 coding standard set down by Moving Pictures Expert Group is adopted largely in digital video field. As a signal source according with the standard, it should send TS(transfer stream) according to the frequency of the TS that have different bitrates correspondingly. Therefore, we develop the programmable divider which use traditional Phase Lock Loop principle and the frequency synthesizer theory. We utilize the CPLD which is developed by Altera and make use of the VHDL to make the design of kernel programme. According to digital TV system requirements, in the range from 3MHz to 30MHz, it can satisfy the desire of the PCI Bus MPEG-2 bitstream sending card with sufficient precision. Now the divider has been used to the PCI Bus MPEG-2 bitstream sending card. It suit well to the MPEG-2 TS output, decode and display system, meeting the demand on the range of frequency, step precision and stabilization of SDTV and HDTV TS. It can decode and play normally.MPEG-2 AAC( ISO/IEC13818-7)is a high efficient coding standard of multi-channel Hi-Fi audio, which provides better reconstructed audio than MP3 and dolby AC-3 at 64kbit per channel. Later, MPEG-2 AAC is absorbed into ISO/IEC14496-3, expanding itself, and become the MPEG-4 AAC. This paper presents the features of this coding technology in detail, at the same time makes the research on its decoding process. It realizes the coding and decoding process of all the profiles of MPEG AAC utilizing the tools and software in existence and the prevailing software developing platform. At last, it makes the analyse of the efficiency of the transcoding from the bitstream of mpeg layer II to AAC.