synthesis_filter.cc

ac3的解码程序

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};



SynthesisFilter::SynthesisFilter (uint32 channelnumber, real factor){
  register real *floatp, *floatp2;

  // initialize v1[] and v2[]:
  for (floatp = v1 + 512, floatp2 = v2 + 512; floatp > v1; )
    *--floatp = *--floatp2 = 0.0;

  channel = channelnumber;
  number_of_samples = range_violations = written_samples = 0;
  actual_v = v1;
  actual_write_pos = 15;
  scalefactor = factor;
}


void SynthesisFilter::compute_new_v(real *new_v){
  {
    unsigned int i;
    register real sample = 0.0, *v = new_v;
    register const real *cooefs;

    // initialize new_v[]:
    *v++ = sample; *v++ = sample; *v++ = sample; *v++ = sample;
    *v++ = sample; *v++ = sample; *v++ = sample; *v++ = sample;
    *v++ = sample; *v++ = sample; *v++ = sample; *v++ = sample;
    *v++ = sample; *v++ = sample; *v++ = sample; *v++ = sample;
    v = new_v + 33;
    *v++ = sample; *v++ = sample; *v++ = sample; *v++ = sample;
    *v++ = sample; *v++ = sample; *v++ = sample; *v++ = sample;
    *v++ = sample; *v++ = sample; *v++ = sample; *v++ = sample;
    *v++ = sample; *v++ = sample; *v++ = sample; *v++ = sample;

    // compute new values:
    for (i = 0; i < number_of_samples; ++i){
      sample = samples[i];
      cooefs = n[subbandnumbers[i]];
      v = new_v;
      // add to new_v[0]-new_v[15]: (new_v[16] remains always 0.0)
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      v = new_v + 33;
      // add to new_v[33]-new_v[47]:
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++; *v++ += sample * *cooefs++;
      *v++ += sample * *cooefs++;
      *v   -= sample;		// new_v[48]
    }
  }

  // fold new values to there boundaries: (a few streams need this)
  {
    register real *v;
    for (v = new_v + 15; v >= new_v; --v)
      if (*v < -1.0)
	*v = -1.0;
      else if (*v > 1.0)
	*v = 1.0;
    for (v = new_v + 48; v >= new_v + 33; --v)
      if (*v < -1.0)
	*v = -1.0;
      else if (*v > 1.0)
	*v = 1.0;
  }

  {
    // copy values -new_v[0-15] to new_v[32-17]:
    register real *v1 = new_v, *v2 = new_v + 33;
    *--v2 = -*v1++; *--v2 = -*v1++; *--v2 = -*v1++; *--v2 = -*v1++;
    *--v2 = -*v1++; *--v2 = -*v1++; *--v2 = -*v1++; *--v2 = -*v1++;
    *--v2 = -*v1++; *--v2 = -*v1++; *--v2 = -*v1++; *--v2 = -*v1++;
    *--v2 = -*v1++; *--v2 = -*v1++; *--v2 = -*v1++; *--v2 = -*v1++;

    // copy values new_v[33-47] to new_v[63-49]:
    v1 = new_v + 33;
    v2 = new_v + 64;
    *--v2 = *v1++; *--v2 = *v1++; *--v2 = *v1++; *--v2 = *v1++;
    *--v2 = *v1++; *--v2 = *v1++; *--v2 = *v1++; *--v2 = *v1++;
    *--v2 = *v1++; *--v2 = *v1++; *--v2 = *v1++; *--v2 = *v1++;
    *--v2 = *v1++; *--v2 = *v1++; *--v2 = *v1++;
  }

  // insert new values into v1[] and v2[]:
  {
    register int i;
    register real *nnv, *nv;

    // insert new_v[0-31] into actual v:
    nnv = new_v;
    nv = actual_v + actual_write_pos;
    for (i = 0; i < 32; ++i, nv += 16)
      *nv = *nnv++;

    // insert new_v[32-63] into other v:
    nv = (actual_v == v1 ? v2 : v1) + actual_write_pos;
    for (; i < 64; ++i, nv += 16)
      *nv = *nnv++;
  }
}


void SynthesisFilter::compute_pcm_samples (Obuffer *buffer){
  int i;
  register real floatreg, *lower_bound, *vp;
  register const real *dp;
  int pcm_sample;

  dp = d;
  lower_bound = actual_v;
  if (actual_write_pos != 15)
    for (i = 0; i < 32; ++i)
    {
      floatreg = 0;
      for (vp = lower_bound + actual_write_pos + 1; vp > lower_bound; )
        floatreg += *--vp * *dp++;
      for (vp += 16; vp > lower_bound + actual_write_pos + 1; )
        floatreg += *--vp * *dp++;

      pcm_sample = (int)(floatreg * scalefactor);
      if (pcm_sample > 32767)
        {
          ++range_violations;
          if (floatreg > max_violation)
            max_violation = floatreg;
          pcm_sample = 32767;
        }
      else if (pcm_sample < -32768)
        {
          ++range_violations;
          if (-floatreg > max_violation)
            max_violation = -floatreg;
          pcm_sample = -32768;
        }
      buffer->append (channel, (int16)pcm_sample);
      lower_bound += 16;
    }
  else
    for (i = 0; i < 32; ++i)
      {
        floatreg = 0;
        for (vp = lower_bound + 16; vp > lower_bound; )
          floatreg += *--vp * *dp++;
        
        pcm_sample = (int)(floatreg * scalefactor);
        if (pcm_sample > 32767)
          {
            ++range_violations;
            if (floatreg > max_violation)
              max_violation = floatreg;
            pcm_sample = 32767;
          }
        else if (pcm_sample < -32768)
          {
            ++range_violations;
            if (-floatreg > max_violation)
              max_violation = -floatreg;
            pcm_sample = -32768;
          }
        buffer->append (channel, (int16)pcm_sample);
        lower_bound += 16;
      }
}


void SynthesisFilter::calculate_pcm_samples (Obuffer *buffer){
  static real new_v[64];

  compute_new_v (new_v);
  compute_pcm_samples (buffer);

  written_samples += 32;
  if (actual_write_pos < 15)
    ++actual_write_pos;
  else
    actual_write_pos = 0;
  actual_v = (actual_v == v1 ? v2 : v1);
  number_of_samples = 0;
}