subband_layer_2.cc

ac3的解码程序

#ifdef DEBUG
  if (samplenumber >= 3){
    // don't call put_next_sample if the previvious call returned True;
    cerr << "Illegal call to SubbandLayer2::put_next_sample()!\n";
    exit (1);
  }
#endif
  if (allocation && channels != right){
    register real sample = (samples[samplenumber] + d) * c;
    if (groupnumber <= 4)
      sample *= scalefactors[scalefactor1];
    else if (groupnumber <= 8)
      sample *= scalefactors[scalefactor2];
    else
      sample *= scalefactors[scalefactor3];
#ifdef DEBUG
    if (sample < -1.0 || sample > 1.0)
      cerr << "WARNING: rescaled subband sample is not in [-1.0, 1.0]\n";
      // this should never occur
#endif
    if (sample < -1.0E-7 || sample > 1.0E-7)
      filter1->input_sample (sample, subbandnumber);
  }

  return (++samplenumber == 3) ? True : False;
}



/******************************/
/*** Intensity Stereo Class ***/
/******************************/

SubbandLayer2IntensityStereo::SubbandLayer2IntensityStereo (uint32 subbandnumber)
: SubbandLayer2 (subbandnumber){
}


void SubbandLayer2IntensityStereo::read_scalefactor_selection (AudioStream *stream, Crc16 *crc){
  if (allocation){
    scfsi = stream->get_bits (2);
    channel2_scfsi = stream->get_bits (2);
    if (crc){
      crc->add_bits (scfsi, 2);
      crc->add_bits (channel2_scfsi, 2);
    }
  }
}


void SubbandLayer2IntensityStereo::read_scalefactor (AudioStream *stream, Header *header){
  if (allocation){
    SubbandLayer2::read_scalefactor (stream, header);
    switch (channel2_scfsi)
    {
      case 0:
	channel2_scalefactor1 = stream->get_bits (6);
	channel2_scalefactor2 = stream->get_bits (6);
	channel2_scalefactor3 = stream->get_bits (6);
	break;
      case 1:
	channel2_scalefactor1 = channel2_scalefactor2 = stream->get_bits (6);
	channel2_scalefactor3 = stream->get_bits (6);
	break;
      case 2:
	channel2_scalefactor1 = channel2_scalefactor2 =
	channel2_scalefactor3 = stream->get_bits (6);
	break;
      case 3:
	channel2_scalefactor1 = stream->get_bits (6);
	channel2_scalefactor2 = channel2_scalefactor3 = stream->get_bits (6);
	break;
    }
    if (channel2_scalefactor1 == 63 || channel2_scalefactor2 == 63 || channel2_scalefactor3 == 63)
      cerr << "WARNING: stream contains an illegal scalefactor!\n";	// MPEG-stream is corrupted!
  }
}


bool SubbandLayer2IntensityStereo::put_next_sample (e_channels channels,
	SynthesisFilter *filter1, SynthesisFilter *filter2){
#ifdef DEBUG
  if (samplenumber >= 3)
  {
    // don't call put_next_sample if the previvious call returned True;
    cerr << "Illegal call to SubbandLayer2::put_next_sample()!\n";
    exit (1);
  }
#endif
  if (allocation)
  {
    register real sample = (samples[samplenumber] + d) * c;
    if (channels == both)
    {
      register float sample2 = sample;
      if (groupnumber <= 4)
      {
	sample *= scalefactors[scalefactor1];
	sample2 *= scalefactors[channel2_scalefactor1];
      }
      else if (groupnumber <= 8)
      {
	sample *= scalefactors[scalefactor2];
	sample2 *= scalefactors[channel2_scalefactor2];
      }
      else
      {
	sample *= scalefactors[scalefactor3];
	sample2 *= scalefactors[channel2_scalefactor3];
      }
#ifdef DEBUG
      if (sample < -1.0 || sample > 1.0 || sample2 < -1.0 || sample2 > 1.0)
	cerr << "WARNING: rescaled subband sample is not in [-1.0, 1.0]\n";
	// this should never occur
#endif
      if (sample < -1.0E-7 || sample > 1.0E-7)
	filter1->input_sample (sample, subbandnumber);
      if (sample2 < -1.0E-7 || sample2 > 1.0E-7)
	filter2->input_sample (sample2, subbandnumber);
    }
    else if (channels == left)
    {
      if (groupnumber <= 4)
	sample *= scalefactors[scalefactor1];
      else if (groupnumber <= 8)
	sample *= scalefactors[scalefactor2];
      else
	sample *= scalefactors[scalefactor3];
#ifdef DEBUG
      if (sample < -1.0 || sample > 1.0)
	cerr << "WARNING: rescaled subband sample is not in [-1.0, 1.0]\n";
	// this should never occur
#endif
      if (sample < -1.0E-7 || sample > 1.0E-7)
	filter1->input_sample (sample, subbandnumber);
    }
    else
    {
      if (groupnumber <= 4)
	sample *= scalefactors[channel2_scalefactor1];
      else if (groupnumber <= 8)
	sample *= scalefactors[channel2_scalefactor2];
      else
	sample *= scalefactors[channel2_scalefactor3];
#ifdef DEBUG
      if (sample < -1.0 || sample > 1.0)
	cerr << "WARNING: rescaled subband sample is not in [-1.0, 1.0]\n";
	// this should never occur
#endif
      if (sample < -1.0E-7 || sample > 1.0E-7)
	filter1->input_sample (sample, subbandnumber);
    }
  }

  if (++samplenumber == 3)
    return True;
  else
    return False;
}



/********************/
/*** Stereo Class ***/
/********************/

SubbandLayer2Stereo::SubbandLayer2Stereo (uint32 subbandnumber)
: SubbandLayer2 (subbandnumber)
{
}


void SubbandLayer2Stereo::read_allocation (AudioStream *stream, Header *header, Crc16 *crc)
{
  uint32 length = get_allocationlength (header);
  allocation = stream->get_bits (length);
  channel2_allocation = stream->get_bits (length);
  if (crc)
  {
    crc->add_bits (allocation, length);
    crc->add_bits (channel2_allocation, length);
  }
}


void SubbandLayer2Stereo::read_scalefactor_selection (AudioStream *stream, Crc16 *crc)
{
  if (allocation)
  {
    scfsi = stream->get_bits (2);
    if (crc)
      crc->add_bits (scfsi, 2);
  }
  if (channel2_allocation)
  {
    channel2_scfsi = stream->get_bits (2);
    if (crc)
      crc->add_bits (channel2_scfsi, 2);
  }
}


void SubbandLayer2Stereo::read_scalefactor (AudioStream *stream, Header *header)
{
  SubbandLayer2::read_scalefactor (stream, header);
  if (channel2_allocation)
  {
    switch (channel2_scfsi)
    {
      case 0:
	channel2_scalefactor1 = stream->get_bits (6);
	channel2_scalefactor2 = stream->get_bits (6);
	channel2_scalefactor3 = stream->get_bits (6);
	break;
      case 1:
	channel2_scalefactor1 = channel2_scalefactor2 = stream->get_bits (6);
	channel2_scalefactor3 = stream->get_bits (6);
	break;
      case 2:
	channel2_scalefactor1 = channel2_scalefactor2 =
	channel2_scalefactor3 = stream->get_bits (6);
	break;
      case 3:
	channel2_scalefactor1 = stream->get_bits (6);
	channel2_scalefactor2 = channel2_scalefactor3 = stream->get_bits (6);
	break;
    }
    if (channel2_scalefactor1 == 63 || channel2_scalefactor2 == 63 || channel2_scalefactor3 == 63)
      cerr << "WARNING: stream contains an illegal scalefactor!\n";	// MPEG-stream is corrupted!

    prepare_sample_reading (header, channel2_allocation, &channel2_grouping,
			    &channel2_quantizationsteps, &channel2_factor,
			    &channel2_codelength, &channel2_c, &channel2_d);
  }
}


bool SubbandLayer2Stereo::read_sampledata (AudioStream *stream){
  bool returnvalue = SubbandLayer2::read_sampledata (stream);

  if (channel2_allocation)
    if (channel2_grouping)
    {
      uint32 samplecode = stream->get_bits (channel2_codelength);
#ifdef DEBUG
      if (samplecode == (1 << channel2_codelength) - 1)
	cerr << "WARNING: stream contains an illegal subband sample!\n";  // MPEG-stream is corrupted!
#endif
      channel2_samples[0] = real (samplecode % channel2_quantizationsteps) * channel2_factor - 1.0;
      samplecode /= channel2_quantizationsteps;
      channel2_samples[1] = real (samplecode % channel2_quantizationsteps) * channel2_factor - 1.0;
      samplecode /= channel2_quantizationsteps;
      channel2_samples[2] = real (samplecode % channel2_quantizationsteps) * channel2_factor - 1.0;
    }
    else
    {
      channel2_samples[0] = real (stream->get_bits (channel2_codelength)) * channel2_factor - 1.0;
#ifdef DEBUG
      if (channel2_samples[0] == (1 << channel2_codelength) - 1)
	cerr << "WARNING: stream contains an illegal subband sample!\n";  // MPEG-stream is corrupted!
#endif
      channel2_samples[1] = real (stream->get_bits (channel2_codelength)) * channel2_factor - 1.0;
#ifdef DEBUG
      if (channel2_samples[1] == (1 << channel2_codelength) - 1)
	cerr << "WARNING: stream contains an illegal subband sample!\n";  // MPEG-stream is corrupted!
#endif
      channel2_samples[2] = real (stream->get_bits (channel2_codelength)) * channel2_factor - 1.0;
#ifdef DEBUG
      if (channel2_samples[2] == (1 << channel2_codelength) - 1)
	cerr << "WARNING: stream contains an illegal subband sample!\n";  // MPEG-stream is corrupted!
#endif
    }
  return returnvalue;
}


bool SubbandLayer2Stereo::put_next_sample (e_channels channels,
					   SynthesisFilter *filter1, SynthesisFilter *filter2)
{
  bool returnvalue = SubbandLayer2::put_next_sample (channels, filter1, filter2);
  if (channel2_allocation && channels != left)
  {
    register real sample = (channel2_samples[samplenumber - 1] + channel2_d) * channel2_c;
    if (groupnumber <= 4)
      sample *= scalefactors[channel2_scalefactor1];
    else if (groupnumber <= 8)
      sample *= scalefactors[channel2_scalefactor2];
    else
      sample *= scalefactors[channel2_scalefactor3];
#ifdef DEBUG
    if (sample < -1.0 || sample > 1.0)
      cerr << "WARNING: rescaled subband sample is not in [-1.0, 1.0]\n";
      // this should never occur
#endif
    if (sample < -1.0E-7 || sample > 1.0E-7)
      if (channels == both)
	filter2->input_sample (sample, subbandnumber);
      else
	filter1->input_sample (sample, subbandnumber);
  }
  return returnvalue;
}