ARM MP3解码源代码.

/*********************************************** copyright by Haia Tech www.haia2004.com ************************************************/ #include <math.h> //#include <stdlib.h> #include "common.h" #include "decode.h" extern struct Granule grle[2][2]; extern Bit_stream_struc bs; extern frame_params fr_ps; struct BandIndex sfBandIndex[3]= { {{0,4,8,12,16,20,24,30,36,44,52,62,74,90,110,134,162,196,238,288,342,418,576}, {0,4,8,12,16,22,30,40,52,66,84,106,136,192}}, {{0,4,8,12,16,20,24,30,36,42,50,60,72,88,106,128,156,190,230,276,330,384,576}, {0,4,8,12,16,22,28,38,50,64,80,100,126,192}}, {{0,4,8,12,16,20,24,30,36,44,54,66,82,102,126,156,194,240,296,364,448,550,576}, {0,4,8,12,16,22,30,42,58,78,104,138,180,192}} }; void decode_info() { layer *hdr = fr_ps.header; int x; hdr->version = getbit(1); hdr->lay = 4-getbit(2); hdr->error_protection = !getbit(1); /* error protect. TRUE/FALSE */ hdr->bitrate_index = getbit(4); hdr->sampling_frequency = getbit(2); hdr->padding = getbit(1); hdr->extension = getbit(1); hdr->mode = getbit(2); hdr->mode_ext = getbit(2); hdr->copyright = getbit(1); hdr->original = getbit(1); hdr->emphasis = getbit(2); } void III_get_side_info(III_side_info_t *si) { int ch, gr, i; int stereo = fr_ps.stereo; si->main_data_begin = getbit(9); //SI 边信息结构 if (stereo == 1) si->private_bits = getbit(5); else si->private_bits = getbit(3); for (ch=0; ch<stereo; ch++) //第二颗粒是否传送信息 for (i=0; i<4; i++) si->scfsi[ch][i] = getbit(1); for (gr=0; gr<2; gr++) { for (ch=0; ch<stereo; ch++) { grle[ch][gr].part2_3_length = getbit(12); grle[ch][gr].big_values = getbit(9); grle[ch][gr].global_gain = getbit(8); grle[ch][gr].scalefac_compress = getbit(4); grle[ch][gr].window_switching_flag = getbit(1); if (grle[ch][gr].window_switching_flag) { //窗开关为1 grle[ch][gr].block_type = getbit(2); grle[ch][gr].mixed_block_flag = getbit(1); for (i=0; i<2; i++) grle[ch][gr].table_select[i] = getbit(5); for (i=0; i<3; i++) grle[ch][gr].subblock_gain[i] = getbit(3); /* Set region_count parameters since they are implicit in this case. */ if (grle[ch][gr].block_type == 0) { // printf("Side info bad: block_type == 0 in split block.\n"); // exit(0); } else if (grle[ch][gr].block_type == 2 && grle[ch][gr].mixed_block_flag == 0) grle[ch][gr].region0_count = 8; /* MI 9; */ //region0和1的缺省配置 else grle[ch][gr].region0_count = 7; /* MI 8; */ grle[ch][gr].region1_count = 20 - grle[ch][gr].region0_count; } else { //窗开关为0 for (i=0; i<3; i++) grle[ch][gr].table_select[i] = getbit(5); grle[ch][gr].region0_count = getbit(4); grle[ch][gr].region1_count = getbit(3); grle[ch][gr].block_type = 0; } grle[ch][gr].preflag = getbit(1); grle[ch][gr].scalefac_scale = getbit(1); grle[ch][gr].count1table_select = getbit(1); } } } struct { int l[5]; int s[3]; } sfbtable = { {0, 6, 11, 16, 21}, {0, 6, 12} }; int slen[2][16]={ {0, 0, 0, 0, 3, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4}, {0, 1, 2, 3, 0, 1, 2, 3, 1, 2, 3, 1, 2, 3, 2, 3} }; void III_get_scale_factors(III_scalefac_t *scalefac, III_side_info_t *si, int gr, int ch) { int sfb, i, window; struct Granule *gr_info = &(grle[ch][gr]); if (gr_info->window_switching_flag && (gr_info->block_type == 2)) { if (gr_info->mixed_block_flag) { /* MIXED */ /* NEW - ag 11/25 */ for (sfb = 0; sfb < 8; sfb++) (*scalefac)[ch].l[sfb] = hgetbits( slen[0][gr_info->scalefac_compress]); //用 slen[0] for (sfb = 3; sfb < 6; sfb++) for (window=0; window<3; window++) (*scalefac)[ch].s[window][sfb] = hgetbits( slen[0][gr_info->scalefac_compress]); //用 slen[0] for (sfb = 6; sfb < 12; sfb++) for (window=0; window<3; window++) (*scalefac)[ch].s[window][sfb] = hgetbits( slen[1][gr_info->scalefac_compress]); //6-11用 slen[1] for (sfb=12,window=0; window<3; window++) (*scalefac)[ch].s[window][sfb] = 0; } else { /* SHORT*/ for (i=0; i<2; i++) for (sfb = sfbtable.s[i]; sfb < sfbtable.s[i+1]; sfb++) for (window=0; window<3; window++) (*scalefac)[ch].s[window][sfb] = hgetbits( slen[i][gr_info->scalefac_compress]); for (sfb=12,window=0; window<3; window++) (*scalefac)[ch].s[window][sfb] = 0; } } else { /* LONG types 0,1,3 */ for (i=0; i<4; i++) { if ((si->scfsi[ch][i] == 0) || (gr == 0)) for (sfb = sfbtable.l[i]; sfb < sfbtable.l[i+1]; sfb++) (*scalefac)[ch].l[sfb] = hgetbits( slen[(i<2)?0:1][gr_info->scalefac_compress]); } (*scalefac)[ch].l[22] = 0; } } int pretab[22] = {0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,2,2,3,3,3,2,0}; void III_dequantize_sample(int is[SBLIMIT][SSLIMIT], double xr[SBLIMIT][SSLIMIT], III_scalefac_t *scalefac, struct Granule *gr_info, int ch) { int ss,sb,cb=0,sfreq=fr_ps.header->sampling_frequency; int next_cb_boundary, cb_begin, cb_width, sign; double is43_table[1024],temp; static int init=1; if(init) { for(init=0;init<1024;init++) is43_table[init]=1.33333333333*log(init); init=0; } /* choose correct scalefactor band per block type, initalize boundary */ if (gr_info->window_switching_flag && (gr_info->block_type == 2) ) if (gr_info->mixed_block_flag) next_cb_boundary=sfBandIndex[sfreq].l[1]; /* LONG blocks: 0,1,3 */ else { next_cb_boundary=sfBandIndex[sfreq].s[1]*3; /* pure SHORT block */ cb_width = sfBandIndex[sfreq].s[1]; cb_begin = 0; } else next_cb_boundary=sfBandIndex[sfreq].l[1]; /* LONG blocks: 0,1,3 */ /* apply formula per block type */ for (sb=0 ; sb < SBLIMIT ; sb++) { //0-31 for (ss=0 ; ss < SSLIMIT ; ss++) { //0-17 /********* 由sb和ss计算cb(比例因子带)和cb_width(比例因子带宽) **************/ if ( (sb*18)+ss == next_cb_boundary) { /* Adjust critical band boundary */ if (gr_info->window_switching_flag && (gr_info->block_type == 2)) { if (gr_info->mixed_block_flag) { if (((sb*18)+ss) == sfBandIndex[sfreq].l[8]) { next_cb_boundary=sfBandIndex[sfreq].s[4]*3; cb = 3; cb_width = sfBandIndex[sfreq].s[cb+1] - sfBandIndex[sfreq].s[cb]; cb_begin = sfBandIndex[sfreq].s[cb]*3; } else if (((sb*18)+ss) < sfBandIndex[sfreq].l[8]) next_cb_boundary = sfBandIndex[sfreq].l[(++cb)+1]; else { next_cb_boundary = sfBandIndex[sfreq].s[(++cb)+1]*3; cb_width = sfBandIndex[sfreq].s[cb+1] - sfBandIndex[sfreq].s[cb]; cb_begin = sfBandIndex[sfreq].s[cb]*3; } } else { next_cb_boundary = sfBandIndex[sfreq].s[(++cb)+1]*3; cb_width = sfBandIndex[sfreq].s[cb+1] - sfBandIndex[sfreq].s[cb]; cb_begin = sfBandIndex[sfreq].s[cb]*3; } } else /* long blocks */ next_cb_boundary = sfBandIndex[sfreq].l[(++cb)+1]; } /***************************************************************************************/ if(is[sb][ss]!=0) { /* Compute overall (global) scaling. */ xr[sb][ss] = (0.25 * (gr_info->global_gain - 210.0)); /* Do long/short dependent scaling operations. */ if (gr_info->window_switching_flag && ( ((gr_info->block_type == 2) && (gr_info->mixed_block_flag == 0)) || ((gr_info->block_type == 2) && gr_info->mixed_block_flag && (sb >= 2)) )) { xr[sb][ss] += (0.25 * -8.0 *gr_info->subblock_gain[(((sb*18)+ss) - cb_begin)/cb_width]); xr[sb][ss] += (0.25 * -2.0 * (1.0+gr_info->scalefac_scale) * (*scalefac)[ch].s[(((sb*18)+ss) - cb_begin)/cb_width][cb])