layer1.c

mips上编译过的mpg 运行正常 环境：AU12

/*
	layer1.c: the layer 1 decoder

	copyright 1995-2007 by the mpg123 project - free software under the terms of the LGPL 2.1
	see COPYING and AUTHORS files in distribution or http://mpg123.org
	initially written by Michael Hipp

	may have a few bugs after last optimization ... 
*/

#include "mpg123lib_intern.h"
#include "getbits.h"

void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],mpg123_handle *fr)
{
  unsigned int *ba=balloc;
  unsigned int *sca = (unsigned int *) scale_index;

  if(fr->stereo == 2) {
    int i;
    int jsbound = fr->jsbound;
    for (i=0;i<jsbound;i++) { 
      *ba++ = getbits(fr, 4);
      *ba++ = getbits(fr, 4);
    }
    for (i=jsbound;i<SBLIMIT;i++)
      *ba++ = getbits(fr, 4);

    ba = balloc;

    for (i=0;i<jsbound;i++) {
      if ((*ba++))
        *sca++ = getbits(fr, 6);
      if ((*ba++))
        *sca++ = getbits(fr, 6);
    }
    for (i=jsbound;i<SBLIMIT;i++)
      if ((*ba++)) {
        *sca++ =  getbits(fr, 6);
        *sca++ =  getbits(fr, 6);
      }
  }
  else {
    int i;
    for (i=0;i<SBLIMIT;i++)
      *ba++ = getbits(fr, 4);
    ba = balloc;
    for (i=0;i<SBLIMIT;i++)
      if ((*ba++))
        *sca++ = getbits(fr, 6);
  }
}

void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
	unsigned int scale_index[2][SBLIMIT],mpg123_handle *fr)
{
  int i,n;
  int smpb[2*SBLIMIT]; /* values: 0-65535 */
  int *sample;
  register unsigned int *ba;
  register unsigned int *sca = (unsigned int *) scale_index;

  if(fr->stereo == 2) {
    int jsbound = fr->jsbound;
    register real *f0 = fraction[0];
    register real *f1 = fraction[1];
    ba = balloc;
    for (sample=smpb,i=0;i<jsbound;i++)  {
      if ((n = *ba++))
        *sample++ = getbits(fr, n+1);
      if ((n = *ba++))
        *sample++ = getbits(fr, n+1);
    }
    for (i=jsbound;i<SBLIMIT;i++) 
      if ((n = *ba++))
        *sample++ = getbits(fr, n+1);

    ba = balloc;
    for (sample=smpb,i=0;i<jsbound;i++) {
      if((n=*ba++))
        *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * fr->muls[n+1][*sca++];
      else
        *f0++ = 0.0;
      if((n=*ba++))
        *f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * fr->muls[n+1][*sca++];
      else
        *f1++ = 0.0;
    }
    for (i=jsbound;i<SBLIMIT;i++) {
      if ((n=*ba++)) {
        real samp = ( ((-1)<<n) + (*sample++) + 1);
        *f0++ = samp * fr->muls[n+1][*sca++];
        *f1++ = samp * fr->muls[n+1][*sca++];
      }
      else
        *f0++ = *f1++ = 0.0;
    }
    for(i=fr->down_sample_sblimit;i<32;i++)
      fraction[0][i] = fraction[1][i] = 0.0;
  }
  else {
    register real *f0 = fraction[0];
    ba = balloc;
    for (sample=smpb,i=0;i<SBLIMIT;i++)
      if ((n = *ba++))
        *sample++ = getbits(fr, n+1);
    ba = balloc;
    for (sample=smpb,i=0;i<SBLIMIT;i++) {
      if((n=*ba++))
        *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * fr->muls[n+1][*sca++];
      else
        *f0++ = 0.0;
    }
    for(i=fr->down_sample_sblimit;i<32;i++)
      fraction[0][i] = 0.0;
  }
}

int do_layer1(mpg123_handle *fr)
{
  int clip=0;
  int i,stereo = fr->stereo;
  unsigned int balloc[2*SBLIMIT];
  unsigned int scale_index[2][SBLIMIT];
  ALIGNED(16) real fraction[2][SBLIMIT];
  int single = fr->single;

  fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : 32;

  if(stereo == 1 || single == SINGLE_MIX) /* I don't see mixing handled here */
    single = SINGLE_LEFT;

  I_step_one(balloc,scale_index,fr);

  for (i=0;i<SCALE_BLOCK;i++)
  {
    I_step_two(fraction,balloc,scale_index,fr);

    if(single != SINGLE_STEREO)
    {
      clip += (fr->synth_mono)( (real *) fraction[single], fr);
    }
    else
    {
      clip += (fr->synth)( (real *) fraction[0], 0, fr, 0);
      clip += (fr->synth)( (real *) fraction[1], 1, fr, 1);
    }
  }

  return clip;
}