/* 
 * Mpeg Layer-1 audio decoder 
 * --------------------------
 * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
 * near unoptimzed ...
 *
 * may have a few bugs after last optimization ... 
 *
 */

#include "mpg123.h"

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

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

    ba = balloc;

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

void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
	unsigned int scale_index[2][SBLIMIT],struct frame *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) {
    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(n+1);
      if ((n = *ba++))
        *sample++ = getbits(n+1);
    }
    for (i=jsbound;i<SBLIMIT;i++) 
      if ((n = *ba++))
        *sample++ = getbits(n+1);

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

void do_layer1(mpgaudio_t *mp)
{
  int clip=0;
  struct frame *fr = &mp->fr;
  int i,stereo = fr->stereo;
  static unsigned int balloc[2*SBLIMIT];
  static unsigned int scale_index[2][SBLIMIT];
  static real fraction[2][SBLIMIT];
  int single = fr->single;
  int num_bytes;

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

  if(stereo == 1 || single == 3)
    single = 0;

  I_step_one(balloc,scale_index,fr);

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

    if(single >= 0) {
      clip += synth_1to1_mono(mp, (real*)fraction[single],mp->osspace,&num_bytes);
    }
    else {
      int p1 = num_bytes;
      clip += synth_1to1(mp, (real*)fraction[0],0,mp->osspace,&p1);
      clip += synth_1to1(mp, (real*)fraction[1],1,mp->osspace,&num_bytes);
    }
  }
  
  if ((!mp->is_output_initialized) || (mp->sample_rate_device != fr->sample_rate)) {

    if (mp->is_output_initialized) 
      mp->ao_output->close(mp->ao_output);

    mp->ao_output->open (mp->ao_output, 16, fr->sample_rate, 
			 stereo-1 ? AO_CAP_MODE_STEREO: AO_CAP_MODE_MONO);
    mp->is_output_initialized = 1;
    mp->sample_rate_device = fr->sample_rate;

    printf ("layer1\n");
  }

  mp->ao_output->write (mp->ao_output, (int16_t*)mp->osspace, num_bytes/(stereo-1 ? 4:2), 
				   mp->pts);
  mp->pts = 0;
				   
}