Research Of MP3 Encoder Technology Based On DSP

Voyage Data Recorder(VDR) records the audio data of the cab and the pivotal cabin,the sound can be replayed by the decoding equipment, so it is very important to find the reason of accident. This thesis puts forward a realizing scheme of MP3 encoder based on Data Signal Processor(DSP),the scheme deal with several pathes of audio that the traditional VDR cannot realize. This scheme has many merits,such as good tone,fine quality and cheap price , convenience to configure.This paper lucubrates theory and process of encoding, detailedly analyse three major aspects of audio compression algorithm, these aspects are subband filter bank and Modified Discrete Cosine Transform (MDCT), quantification and coding, form of frame. The coding can control the quantized values of subband and corresponding square difference of rebuild error,making matching bitstream more accurate with message source counts characteristic of per subband;Besides, quantization noise of per subband is fettered within the subband, input signal of subband of lesser power is avoided from covering up by quantization noise of other subband;At the same time, noise frequency spectrum is formed by ear's subjective characteristic according to coding algorithm,and thus,coding system performance is improved greatly.The thesis also puts forward hardware and software design scheme of MP3 encoder based on DM642 DSP. Firstly, main processor module, acquisition circuit module of audio and Ethernet circuit module are expounded. Software design is accomplished on the embed operating system DSP/BIOS,on the basis, audio coding chip and Ethernet interface chip are configured and initialized with CSL(Chip Support Library) and NDK(Networking Developing Kit); Furthermore, the function of subprogram models are detailedly expounded; Finally, process of compiling ,debugging and replantation is discussed, the paper also provides optimizing scheme of MP3 encoder and the results of experiment.