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00001 /*
00002     layer1.c: the layer 1 decoder
00003 
00004     copyright 1995-2009 by the mpg123 project - free software under the terms of the LGPL 2.1
00005     see COPYING and AUTHORS files in distribution or http://mpg123.org
00006     initially written by Michael Hipp
00007 
00008     may have a few bugs after last optimization ... 
00009 */
00010 
00011 #include "mpg123lib_intern.h"
00012 #include "getbits.h"
00013 
00014 void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],mpg123_handle *fr)
00015 {
00016     unsigned int *ba=balloc;
00017     unsigned int *sca = (unsigned int *) scale_index;
00018 
00019     if(fr->stereo == 2)
00020     {
00021         int i;
00022         int jsbound = fr->jsbound;
00023         for(i=0;i<jsbound;i++)
00024         { 
00025             *ba++ = getbits(fr, 4);
00026             *ba++ = getbits(fr, 4);
00027         }
00028         for(i=jsbound;i<SBLIMIT;i++) *ba++ = getbits(fr, 4);
00029 
00030         ba = balloc;
00031 
00032         for(i=0;i<jsbound;i++)
00033         {
00034             if ((*ba++))
00035                 *sca++ = getbits(fr, 6);
00036             if ((*ba++))
00037                 *sca++ = getbits(fr, 6);
00038         }
00039         for (i=jsbound;i<SBLIMIT;i++)
00040         if((*ba++))
00041         {
00042             *sca++ =  getbits(fr, 6);
00043             *sca++ =  getbits(fr, 6);
00044         }
00045     }
00046     else
00047     {
00048         int i;
00049         for(i=0;i<SBLIMIT;i++) *ba++ = getbits(fr, 4);
00050 
00051         ba = balloc;
00052         for (i=0;i<SBLIMIT;i++)
00053         if ((*ba++))
00054         *sca++ = getbits(fr, 6);
00055     }
00056 }
00057 
00058 void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT], unsigned int scale_index[2][SBLIMIT],mpg123_handle *fr)
00059 {
00060     int i,n;
00061     int smpb[2*SBLIMIT]; /* values: 0-65535 */
00062     int *sample;
00063     register unsigned int *ba;
00064     register unsigned int *sca = (unsigned int *) scale_index;
00065 
00066     if(fr->stereo == 2)
00067     {
00068         int jsbound = fr->jsbound;
00069         register real *f0 = fraction[0];
00070         register real *f1 = fraction[1];
00071         ba = balloc;
00072         for(sample=smpb,i=0;i<jsbound;i++)
00073         {
00074             if((n = *ba++)) *sample++ = getbits(fr, n+1);
00075 
00076             if((n = *ba++)) *sample++ = getbits(fr, n+1);
00077         }
00078         for(i=jsbound;i<SBLIMIT;i++) 
00079         if((n = *ba++))
00080         *sample++ = getbits(fr, n+1);
00081 
00082         ba = balloc;
00083         for(sample=smpb,i=0;i<jsbound;i++)
00084         {
00085             if((n=*ba++))
00086             *f0++ = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15( ((-1)<<n) + (*sample++) + 1), fr->muls[n+1][*sca++]);
00087             else *f0++ = DOUBLE_TO_REAL(0.0);
00088 
00089             if((n=*ba++))
00090             *f1++ = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15( ((-1)<<n) + (*sample++) + 1), fr->muls[n+1][*sca++]);
00091             else *f1++ = DOUBLE_TO_REAL(0.0);
00092         }
00093         for(i=jsbound;i<SBLIMIT;i++)
00094         {
00095             if((n=*ba++))
00096             {
00097                 real samp = DOUBLE_TO_REAL_15( ((-1)<<n) + (*sample++) + 1);
00098                 *f0++ = REAL_MUL_SCALE_LAYER12(samp, fr->muls[n+1][*sca++]);
00099                 *f1++ = REAL_MUL_SCALE_LAYER12(samp, fr->muls[n+1][*sca++]);
00100             }
00101             else *f0++ = *f1++ = DOUBLE_TO_REAL(0.0);
00102         }
00103         for(i=fr->down_sample_sblimit;i<32;i++)
00104         fraction[0][i] = fraction[1][i] = 0.0;
00105     }
00106     else
00107     {
00108         register real *f0 = fraction[0];
00109         ba = balloc;
00110         for(sample=smpb,i=0;i<SBLIMIT;i++)
00111         if ((n = *ba++))
00112         *sample++ = getbits(fr, n+1);
00113 
00114         ba = balloc;
00115         for(sample=smpb,i=0;i<SBLIMIT;i++)
00116         {
00117             if((n=*ba++))
00118             *f0++ = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15( ((-1)<<n) + (*sample++) + 1), fr->muls[n+1][*sca++]);
00119             else *f0++ = DOUBLE_TO_REAL(0.0);
00120         }
00121         for(i=fr->down_sample_sblimit;i<32;i++)
00122         fraction[0][i] = DOUBLE_TO_REAL(0.0);
00123     }
00124 }
00125 
00126 int do_layer1(mpg123_handle *fr)
00127 {
00128     int clip=0;
00129     int i,stereo = fr->stereo;
00130     unsigned int balloc[2*SBLIMIT];
00131     unsigned int scale_index[2][SBLIMIT];
00132     real (*fraction)[SBLIMIT] = fr->layer1.fraction; /* fraction[2][SBLIMIT] */
00133     int single = fr->single;
00134 
00135     fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : 32;
00136 
00137     if(stereo == 1 || single == SINGLE_MIX) /* I don't see mixing handled here */
00138     single = SINGLE_LEFT;
00139 
00140     I_step_one(balloc,scale_index,fr);
00141 
00142     for(i=0;i<SCALE_BLOCK;i++)
00143     {
00144         I_step_two(fraction,balloc,scale_index,fr);
00145 
00146         if(single != SINGLE_STEREO)
00147         clip += (fr->synth_mono)(fraction[single], fr);
00148         else
00149         clip += (fr->synth_stereo)(fraction[0], fraction[1], fr);
00150     }
00151 
00152     return clip;
00153 }
00154 
00155
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