MP3 Decoder

/********************************************************************** * ISO MPEG Audio Subgroup Software Simulation Group (1991-1996) * ISO 11172-3 MPEG-1 Audio Codec * Revision 4.4 March 1996 * * decode.c **********************************************************************/ /********************************************************************** * changes made since last update: * * date programmers comment * * 2/25/91 Douglas Wong, start of version 1.0 records * * Davis Pan * * 3/06/91 Douglas Wong rename: setup.h to dedef.h * * dfilter to defilter * * dwindow to dewindow * * integrated "quantizer", "scalefactor" * * combined window_samples routine into * * filter samples * * 3/31/91 Bill Aspromonte replaced read_filter by * * create_syn_filter and introduced a * * new Sub-Band Synthesis routine called * * SubBandSynthesis() * * 5/10/91 Vish (PRISM) Ported to Macintosh and Unix. * * Changed "out_fifo()" so that last * * unfilled block is also written out. * * "create_syn_filter()" was modified so * * that calculation precision is same as * * in specification tables. * * Changed "decode_scale()" to reflect * * specifications. * * Removed all routines used by * * "synchronize_buffer()". This is now * * replaced by "seek_sync()". * * Incorporated Jean-Georges Fritsch's * * "bitstream.c" package. * * Deleted "reconstruct_sample()". * * 27jun91 dpwe (Aware) Passed outFile and &sampFrames as * * args to out_fifo() - were global. * * Moved "alloc_*" reader to common.c. * * alloc, sblimit, stereo passed via new * * 'frame_params struct (were globals). * * Added JOINT STEREO decoding, lyrs I&II* * Affects: decode_bitalloc,buffer_samps * * Plus a few other cleanups. * * 6/10/91 Earle Jennings conditional expansion added in * * II_dequantize_sample to handle range * * problems in MSDOS version * * 8/8/91 Jens Spille Change for MS-C6.00 * *10/1/91 S.I. Sudharsanan, Ported to IBM AIX platform. * * Don H. Lee, * * Peter W. Farrett * *10/3/91 Don H. Lee implemented CRC-16 error protection * * newly introduced functions are * * buffer_CRC and recover_CRC_error. * * 2/11/92 W. Joseph Carter Ported new code to Macintosh. Most * * important fixes involved changing * * 16-bit ints to long or unsigned in * * bit alloc routines for quant of 65535 * * and passing proper function args. * * Removed "Other Joint Stereo" option * * and made bitrate be total channel * * bitrate, irrespective of the mode. * * Fixed many small bugs & reorganized. * * 7/27/92 Juan Pineda Bug fix in SubBandSynthesis() * *--------------------------------------------------------------------* * 6/14/92 Juan Pineda Layer III decoding routines added. * * Amit Gulati Follows CD 3-11172 rev2. Contains * * hacks deal with evolving available * * layerIII bitstreams. Some (minor) * * modification of prior LI&II code. * * 10/25/92 Amit Gulati Updated layerIII routines. Added code * * for subblock_gain, switched block * * modes, stereo pre-processing. * * Corrected sign bits for huffman * * decoding of quadruples region and * * adjusted gain factor in III_dequant. * * 11/21/92 Amit Gulati Several layerIII bugs fixed. * * 12/15/92 Amit Gulati Corrected reordering (indexing) * * Stan Searing within IMDCT routine. * * 8/24/93 Masahiro Iwadare Included IS modification in Layer III.* * Changed for 1 pass decoding. * * 9/07/93 Toshiyuki Ishino Integrated Layer III with Ver 3.9. * *--------------------------------------------------------------------* * 11/20/93 Masahiro Iwadare Integrated Layer III with Ver 4.0. * *--------------------------------------------------------------------* * 7/14/94 Juergen Koller Bug fixes in Layer III code * *--------------------------------------------------------------------* * 08/11/94 IIS Bug fixes in Layer III code * *--------------------------------------------------------------------* * 9/20/94 Davis Pan Modification to avoid premature * * synchword detection * *--------------------------------------------------------------------* * 11/09/94 Jon Rowlands Merged premature synchword detection * * fix into layer III code version * **********************************************************************/ #include "common.h" #include "decoder.h" #include "huffman.h" /*************************************************************** /* /* This module contains the core of the decoder ie all the /* computational routines. (Layer I and II only) /* Functions are common to both layer unless /* otherwise specified. /* /***************************************************************/ /***************************************************************** /* /* The following routines decode the system information /* /****************************************************************/ /************ Layer I, Layer II & Layer III ******************/ void decode_info(bs, fr_ps) Bit_stream_struc *bs; frame_params *fr_ps; { unsigned int bits; layer *hdr = fr_ps->header; while( (bits=getbits(bs,8)) == 255); /*discard leading 0xFF's of syncword*/ hdr->bitrate_index = bits & 0xF; bits = bits >> 4; switch(bits) { case 0: hdr->version = 0; hdr->lay = 4; hdr->error_protection = 1; break; case 1: hdr->version = 0; hdr->lay = 4; hdr->error_protection = 0; break; case 2: hdr->version = 0; hdr->la