Software Design Of Audio Decoding In Car MP3 Player

At present, car MP3 players, like other portable MP3 players, uses the special decode chip to decode in design. Using the decode chip, there are some serious disadvantages, such as flexibility is low, the system can not be upgraded, it is difficult to adapt to the new audio compression format. therefore, it is not a good option; The ARM processor with its powerful processing capabilities and low power consumption, has become the mainstream chip in the filed of embedded. can be well used in MP3 player design.Currently, for the high cost and system upgrades difficult issues of using decode chip in car MP3 player, designed a car MP3 player solution of general hardware + software decode. Hareware using ARM Cortex-M3 core 32-bit microprocessor LPC1766 + D/A conversion chip UDA1341TS achieved, Software decoding using C language programming achieved. The system read MP3 file from U disk or SD card to the processor, and decode MP3 file by decoding process for realtime, then put the decode data through the IIS interface output, then via UDA1341TS to DA conversion in order to restore the audio analog signal. Through keys, we can make the songs play, stop, select for last, select for next, fast-forward operation.This article first describes the MP3 file format and the decoding algorithm. And then set the system solutions and the overall design of software. On this basis, put the program divided into two parts of decode and play to design separately. The software of decode part is designed in nine parts in strict accordance with the decoding algorithm. The play part include the IIS audio interface, UDA1341TS and DMA, design the initialize program of them separately. Finally, combine the various parts of the software an debugging. The results show that using software to MP3 decode, not only operation is stable and reliable, sound quality is better, but also the system is easy to upgrade. In addition, the decoding program portability higher, can easy to transplant to other devices that support the audio play, and has guiding significance to the development of multi-media player in the future.