A DSP-based decompressor unit for high-fidelity MPEG-Audio over TCP/IP networks

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Appendix D - The main C sourcecode

The program was written with some object-orientation in mind, which means that all functions that operate on a certain structure, has the structure's name as prefix in the function name, for example "Bitstream_get" which gets bits from a bitstream structure.

There is a sea of conditional compile directives in the source, because of its multi-platform compiling. It was designed to be compileable on both Linux, Windows and the DSP of course. As a result, it can be quite difficult to browse some parts of the code without looking closer. The code was optimized for realtime playback on a DSP, not for readability or expandability.

The following files constitute the main C sourcecode. The tablefiles for the transforms are omitted - they can be autogenerated from within the main program using a #define statement. Please note that these files are presented as-is for reference only, they don't contain a Makefile and might contain errors. Also note that they cannot run on the DSP in realtime without hand-made assembler optimizing. The assembler version is not presented in the thesis because it is copyrighted. If you are just looking for the source-code to an mp3 player, I suggest taking a look at some of the other freely available players with source, like amp; see the link below.

mp3dec.h - The main header file defining the structures and functions in the decoder
mp3dec.c - The main source file, including the main loop and most decoding functions
mp3dec_D.h - The windowing function data
huff.c - The huffman decoder (speed-up ideas in this were borrowed from Amp by Tomislav Uzelac)
huffman.h - Tablefile for the huffman decoder
fastimdct.c - The optimized IMDCT transform
fastsb.c - The optimized "polyphase subband transform", really another IMDCT
windowing.c - The output filtering function

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