Research On Optimal Design And Implement Of MPEG-4 AAC Decoder In DSP

The development of computer and network improves the technique of audio-videoapplied in the multi-media, network, visual telephone, monitor ,road etc. MPEG4AAC( Advance Audio Coding), as the kernel of MPEG-4 audio standard, can encode anddecode high quality under 64kbps. It support over 48 audio channels,16 low frequencychannels, 16 multi-dub and multi-language channels, and 16 data streams.so it play a keyrole in many fields.The DM642,which is a multimedia DSP, posses highly clock, highlyparallel instruction set, these performances make possible of realizing MPEG4 AACreal-time decoder. The algorithms of MPEG4 audio standard are discussed. And the AAC decoder isrealized on the DM642. First, we introduce the principle of MPEG4 AAC standard, anddiscussed the key decoding modules; Then we introduce hardware system of DM642 EVM; Third, we introduce the correlative optimize technique; Last, from the objectivity estimateaspect, we make analyse the audio quality of the output of AAC decoder. MPEG4 AAC decoder is made of Noiseless decoding, inverse quantity, apply scalefactor, union stero decoding, temporal noise shaping, long term predict, inverse filter bankevery modules has quite large operations. In order that AAC can be applied to network,visual telephone, IPTV domain, that how to improve efficiency and sunning speed is thekey point. Finally we implement the AAC decoder on the DM642 EVM by programoptimizing. Finally, we give the realized results, analyze and technique target of the decoderalgorithms on the DM642, including the audio objective evaluation. The Experiments showthat there no difference between decoded signal and original subjectively, and similar withMOS objectively. The decoder has certain applied value.