The Research Of MPEG-4 AAC Audio Decoder Based On Fixed-point DSP

MPEG audio coding systems have been applied widely in the transmission, storage and broadcasting of digital audio signal. With the progress of society, higher audio quality of audio coding, systems are expected. MPEG-4 AAC has become the core algorithm of high quality audio coding in MPEG-4.It represents the most advanced technology of the perceptual audio coding. AAC can be used in many different fields, such as digital audio, digital broadcast, multimedia, etc.First, introduce the international standard of MPEG-4 AAC and the technology of DSP respectively. Then focus on the development process of implementing the MPEG-4 AAC decoder on a single DSP chip and the technologies it concerned. MPEG-4 AAC algorithm mainly consists of several modules, such as gain control module, filterbank module, prediction module and quantization coding module. Each module is very complicated with a heavy computation. To fully exploit the advantage of TMSDM642 fixed DSP and improve the efficiency of the program, we must modify float AAC algorithm to fixed AAC algorithm. On the other hand, it is necessary to optimize the structure of the program and simplify the algorithm while maintaining the audio quality. Finally implement the MPEG-4 AAC decoder on a chip of TMSDM642 DSP.Finally, experimental results have shown that all the improvements of MPEG-4 LC-AAC decoder show an excellent performance in calculating speed and stability.