layer3.c

一个将mp3/mp2文件解压成wav文件的源码

static void dct12(real *in,real *rawout1,real *rawout2,register real *wi,register real *ts)
{
#define DCT12_PART1 \
             in5 = in[5*3];  \
     in5 += (in4 = in[4*3]); \
     in4 += (in3 = in[3*3]); \
     in3 += (in2 = in[2*3]); \
     in2 += (in1 = in[1*3]); \
     in1 += (in0 = in[0*3]); \
                             \
     in5 += in3; in3 += in1; \
                             \
     in2 *= COS6_1; \
     in3 *= COS6_1; \

#define DCT12_PART2 \
     in0 += in4 * COS6_2; \
                          \
     in4 = in0 + in2;     \
     in0 -= in2;          \
                          \
     in1 += in5 * COS6_2; \
                          \
     in5 = (in1 + in3) * tfcos12[0]; \
     in1 = (in1 - in3) * tfcos12[2]; \
                         \
     in3 = in4 + in5;    \
     in4 -= in5;         \
                         \
     in2 = in0 + in1;    \
     in0 -= in1;


   {
     real in0,in1,in2,in3,in4,in5;
     register real *out1 = rawout1;
     ts[SBLIMIT*0] = out1[0]; ts[SBLIMIT*1] = out1[1]; ts[SBLIMIT*2] = out1[2];
     ts[SBLIMIT*3] = out1[3]; ts[SBLIMIT*4] = out1[4]; ts[SBLIMIT*5] = out1[5];

     DCT12_PART1

     {
       real tmp0,tmp1 = (in0 - in4);
       {
         real tmp2 = (in1 - in5) * tfcos12[1];
         tmp0 = tmp1 + tmp2;
         tmp1 -= tmp2;
       }
       ts[(17-1)*SBLIMIT] = out1[17-1] + tmp0 * wi[11-1];
       ts[(12+1)*SBLIMIT] = out1[12+1] + tmp0 * wi[6+1];
       ts[(6 +1)*SBLIMIT] = out1[6 +1] + tmp1 * wi[1];
       ts[(11-1)*SBLIMIT] = out1[11-1] + tmp1 * wi[5-1];
     }

     DCT12_PART2

     ts[(17-0)*SBLIMIT] = out1[17-0] + in2 * wi[11-0];
     ts[(12+0)*SBLIMIT] = out1[12+0] + in2 * wi[6+0];
     ts[(12+2)*SBLIMIT] = out1[12+2] + in3 * wi[6+2];
     ts[(17-2)*SBLIMIT] = out1[17-2] + in3 * wi[11-2];

     ts[(6+0)*SBLIMIT]  = out1[6+0] + in0 * wi[0];
     ts[(11-0)*SBLIMIT] = out1[11-0] + in0 * wi[5-0];
     ts[(6+2)*SBLIMIT]  = out1[6+2] + in4 * wi[2];
     ts[(11-2)*SBLIMIT] = out1[11-2] + in4 * wi[5-2];
  }

  in++;

  {
     real in0,in1,in2,in3,in4,in5;
     register real *out2 = rawout2;

     DCT12_PART1

     {
       real tmp0,tmp1 = (in0 - in4);
       {
         real tmp2 = (in1 - in5) * tfcos12[1];
         tmp0 = tmp1 + tmp2;
         tmp1 -= tmp2;
       }
       out2[5-1] = tmp0 * wi[11-1];
       out2[0+1] = tmp0 * wi[6+1];
       ts[(12+1)*SBLIMIT] += tmp1 * wi[1];
       ts[(17-1)*SBLIMIT] += tmp1 * wi[5-1];
     }

     DCT12_PART2

     out2[5-0] = in2 * wi[11-0];
     out2[0+0] = in2 * wi[6+0];
     out2[0+2] = in3 * wi[6+2];
     out2[5-2] = in3 * wi[11-2];

     ts[(12+0)*SBLIMIT] += in0 * wi[0];
     ts[(17-0)*SBLIMIT] += in0 * wi[5-0];
     ts[(12+2)*SBLIMIT] += in4 * wi[2];
     ts[(17-2)*SBLIMIT] += in4 * wi[5-2];
  }

  in++;

  {
     real in0,in1,in2,in3,in4,in5;
     register real *out2 = rawout2;
     out2[12]=out2[13]=out2[14]=out2[15]=out2[16]=out2[17]=0.0;

     DCT12_PART1

     {
       real tmp0,tmp1 = (in0 - in4);
       {
         real tmp2 = (in1 - in5) * tfcos12[1];
         tmp0 = tmp1 + tmp2;
         tmp1 -= tmp2;
       }
       out2[11-1] = tmp0 * wi[11-1];
       out2[6 +1] = tmp0 * wi[6+1];
       out2[0+1] += tmp1 * wi[1];
       out2[5-1] += tmp1 * wi[5-1];
     }

     DCT12_PART2

     out2[11-0] = in2 * wi[11-0];
     out2[6 +0] = in2 * wi[6+0];
     out2[6 +2] = in3 * wi[6+2];
     out2[11-2] = in3 * wi[11-2];

     out2[0+0] += in0 * wi[0];
     out2[5-0] += in0 * wi[5-0];
     out2[0+2] += in4 * wi[2];
     out2[5-2] += in4 * wi[5-2];
  }
}

/*
 * III_hybrid
 */
static void III_hybrid(real fsIn[SBLIMIT][SSLIMIT],real tsOut[SSLIMIT][SBLIMIT],
   int ch,struct gr_info_s *gr_info)
{
   real *tspnt = (real *) tsOut;
   real (*block)[2][SBLIMIT*SSLIMIT] = gmp->hybrid_block;
   int *blc = gmp->hybrid_blc;
   real *rawout1,*rawout2;
   int bt;
   int sb = 0;

   {
     int b = blc[ch];
     rawout1=block[b][ch];
     b=-b+1;
     rawout2=block[b][ch];
     blc[ch] = b;
   }


   if(gr_info->mixed_block_flag) {
     sb = 2;
     dct36(fsIn[0],rawout1,rawout2,win[0],tspnt);
     dct36(fsIn[1],rawout1+18,rawout2+18,win1[0],tspnt+1);
     rawout1 += 36; rawout2 += 36; tspnt += 2;
   }

   bt = gr_info->block_type;
   if(bt == 2) {
     for (; sb<gr_info->maxb; sb+=2,tspnt+=2,rawout1+=36,rawout2+=36) {
       dct12(fsIn[sb],rawout1,rawout2,win[2],tspnt);
       dct12(fsIn[sb+1],rawout1+18,rawout2+18,win1[2],tspnt+1);
     }
   }
   else {
     for (; sb<gr_info->maxb; sb+=2,tspnt+=2,rawout1+=36,rawout2+=36) {
       dct36(fsIn[sb],rawout1,rawout2,win[bt],tspnt);
       dct36(fsIn[sb+1],rawout1+18,rawout2+18,win1[bt],tspnt+1);
     }
   }

   for(;sb<SBLIMIT;sb++,tspnt++) {
     int i;
     for(i=0;i<SSLIMIT;i++) {
       tspnt[i*SBLIMIT] = *rawout1++;
       *rawout2++ = 0.0;
     }
   }
}

/*
 * main layer3 handler
 */
int do_layer3(struct frame *fr, unsigned char *pcm_sample, int *pcm_point)
{
  int gr, ch, ss, clip = 0;
  int scalefacs[2][39]; /* max 39 for short[13][3] mode, mixed: 38, long: 22 */
  struct III_sideinfo sideinfo;
  int stereo = fr->stereo;
  int single = fr->single;
  int ms_stereo,i_stereo;
  int sfreq = fr->sampling_frequency;
  int stereo1,granules;



  if(stereo == 1) { /* stream is mono */
    stereo1 = 1;
    single = 0;
  }
  else if(single >= 0) /* stream is stereo, but force to mono */
    stereo1 = 1;
  else
    stereo1 = 2;

  if(fr->mode == MPG_MD_JOINT_STEREO) {
    ms_stereo = fr->mode_ext & 0x2;
    i_stereo  = fr->mode_ext & 0x1;
  }
  else
    ms_stereo = i_stereo = 0;


  if(fr->lsf) {
    granules = 1;
    if (III_get_side_info_2(&sideinfo,stereo,ms_stereo,sfreq,single))
#ifdef BE_QUIET
      return -1;
#else
      ;
#endif
  }
  else {
    granules = 2;
#ifdef MPEG1
    if (III_get_side_info_1(&sideinfo,stereo,ms_stereo,sfreq,single))
#ifdef BE_QUIET
      return -1;
#else
      ;
#endif

#else
#ifndef BE_QUIET
    fprintf(stderr,"Not supported\n");
#endif
#endif
  }

  if(set_pointer(sideinfo.main_data_begin) == MP3_ERR)
    return 0;


  for (gr=0;gr<granules;gr++)
  {
    static real hybridIn[2][SBLIMIT][SSLIMIT];
    static real hybridOut[2][SSLIMIT][SBLIMIT];

    {
      struct gr_info_s *gr_info = &(sideinfo.ch[0].gr[gr]);
      long part2bits;
      if(fr->lsf)
        part2bits = III_get_scale_factors_2(scalefacs[0],gr_info,0);
      else {
#ifdef MPEG1
        part2bits = III_get_scale_factors_1(scalefacs[0],gr_info);
#else
#ifndef BE_QUIET
	fprintf(stderr,"Not supported\n");
#endif
#endif
      }
#ifdef HAVEGTK
      if (gtkflag) {
	int i;
	for (i=0; i<39; i++)
	  pinfo->sfb_s[gr][0][i]=scalefacs[0][i];
      }
#endif
      if(III_dequantize_sample(hybridIn[0], scalefacs[0],gr_info,sfreq,part2bits))
#ifndef BE_QUIET
        return clip;
#else
        return 0;
#endif
    }
    if(stereo == 2) {
      struct gr_info_s *gr_info = &(sideinfo.ch[1].gr[gr]);
      long part2bits;
      if(fr->lsf)
        part2bits = III_get_scale_factors_2(scalefacs[1],gr_info,i_stereo);
      else {
#ifdef MPEG1
        part2bits = III_get_scale_factors_1(scalefacs[1],gr_info);
#else
#ifndef BE_QUIET
	fprintf(stderr,"Not supported\n");
#endif
#endif
      }
#ifdef HAVEGTK
      if (gtkflag) {
	int i;
	for (i=0; i<39; i++)
	  pinfo->sfb_s[gr][1][i]=scalefacs[1][i];
      }
#endif

      if(III_dequantize_sample(hybridIn[1],scalefacs[1],gr_info,sfreq,part2bits))
#ifndef BE_QUIET
        return clip;
#else
        return 0;
#endif

      if(ms_stereo) {
        int i;
        for(i=0;i<SBLIMIT*SSLIMIT;i++) {
          real tmp0,tmp1;
          tmp0 = ((real *) hybridIn[0])[i];
          tmp1 = ((real *) hybridIn[1])[i];
          ((real *) hybridIn[1])[i] = tmp0 - tmp1;
          ((real *) hybridIn[0])[i] = tmp0 + tmp1;
        }
      }

      if(i_stereo)
        III_i_stereo(hybridIn,scalefacs[1],gr_info,sfreq,ms_stereo,fr->lsf);

      if(ms_stereo || i_stereo || (single == 3) ) {
        if(gr_info->maxb > sideinfo.ch[0].gr[gr].maxb)
          sideinfo.ch[0].gr[gr].maxb = gr_info->maxb;
        else
          gr_info->maxb = sideinfo.ch[0].gr[gr].maxb;
      }

      switch(single) {
        case 3:
          {
            register int i;
            register real *in0 = (real *) hybridIn[0],*in1 = (real *) hybridIn[1];
            for(i=0;i<SSLIMIT*gr_info->maxb;i++,in0++)
              *in0 = (*in0 + *in1++); /* *0.5 done by pow-scale */
          }
          break;
        case 1:
          {
            register int i;
            register real *in0 = (real *) hybridIn[0],*in1 = (real *) hybridIn[1];
            for(i=0;i<SSLIMIT*gr_info->maxb;i++)
              *in0++ = *in1++;
          }
          break;
      }
    }

#ifdef HAVEGTK
    if (gtkflag) {
    extern int tabsel_123[2][3][16];
    extern int pretab[21];
    int i,j,sb;
    float ifqstep;

    for (ch=0;ch<stereo1;ch++) {
      struct gr_info_s *gr_info = &(sideinfo.ch[ch].gr[gr]);
      ifqstep = ( pinfo->scalefac_scale[gr][ch] == 0 ) ? .5 : 1.0;
      if (2==gr_info->block_type) {
	for (i=0; i<3; i++) {
	  for (sb=0; sb<12; sb++) {
	    j = 3*sb+i;
	    /*
           is_p = scalefac[sfb*3+lwin-gr_info->mixed_block_flag];
	    */
	    /* scalefac was copied into pinfo->sfb_s[] above */
	    pinfo->sfb_s[gr][ch][j] = -ifqstep*pinfo->sfb_s[gr][ch][j-gr_info->mixed_block_flag];
	    pinfo->sfb_s[gr][ch][j] -= 2*(pinfo->sub_gain[gr][ch][i]);
	  }
	  pinfo->sfb_s[gr][ch][3*sb+i] = - 2*(pinfo->sub_gain[gr][ch][i]);
	}
      }else{
	for (sb=0; sb<21; sb++) {
	  /* scalefac was copied into pinfo->sfb[] above */
	  pinfo->sfb[gr][ch][sb] = pinfo->sfb_s[gr][ch][sb];
	  if (gr_info->preflag) pinfo->sfb[gr][ch][sb] += pretab[sb];
	  pinfo->sfb[gr][ch][sb] *= -ifqstep;
	}
      }
    }



    pinfo->bitrate =
      tabsel_123[fr->lsf][fr->lay-1][fr->bitrate_index];
    pinfo->sampfreq = freqs[sfreq];
    pinfo->emph = fr->emphasis;
    pinfo->crc = fr->error_protection;
    pinfo->padding = fr->padding;
    pinfo->stereo = fr->stereo;
    pinfo->js =   (fr->mode == MPG_MD_JOINT_STEREO);
    pinfo->ms_stereo = ms_stereo;
    pinfo->i_stereo = i_stereo;
    pinfo->maindata = sideinfo.main_data_begin;

    for(ch=0;ch<stereo1;ch++) {
      struct gr_info_s *gr_info = &(sideinfo.ch[ch].gr[gr]);
      pinfo->mixed[gr][ch] = gr_info->mixed_block_flag;
      pinfo->mpg123blocktype[gr][ch]=gr_info->block_type;
      pinfo->mainbits[gr][ch] = gr_info->part2_3_length;
      if (gr==1) pinfo->scfsi[ch] = gr_info->scfsi;
    }
    for(ch=0;ch<stereo1;ch++) {
      int j=0;
      for (sb=0;sb<SBLIMIT;sb++)
	for(ss=0;ss<SSLIMIT;ss++,j++)
	  pinfo->mpg123xr[gr][ch][j]=hybridIn[ch][sb][ss];
    }
  }

#endif

    for(ch=0;ch<stereo1;ch++) {
      struct gr_info_s *gr_info = &(sideinfo.ch[ch].gr[gr]);
      III_antialias(hybridIn[ch],gr_info);
      III_hybrid(hybridIn[ch], hybridOut[ch], ch,gr_info);
    }

    for(ss=0;ss<SSLIMIT;ss++) {
      if(single >= 0) {
        clip += synth_1to1_mono(hybridOut[0][ss],pcm_sample,pcm_point);
      }
      else {
        int p1 = *pcm_point;
        clip += synth_1to1(hybridOut[0][ss],0,pcm_sample,&p1);
        clip += synth_1to1(hybridOut[1][ss],1,pcm_sample,pcm_point);
      }
    }
  }

#ifndef BE_QUIET
  return clip;
#else
  return 0;
#endif
}