subband_layer_1.cc

ac3的解码程序

/*
   File: subband_layer_1.cc

   Description:

*/
   
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fstream.h>
#ifdef IRIX
#include <dmedia/audio.h>
#endif
#ifdef SOLARIS
#include <sys/audioio.h>
#endif

#include "athread.hh"

#include "error.hh"
#include "debug.hh"
#include "util.hh"

#include "sync.hh"
#include "mpeg2const.hh"
#include "mpeg2buff.hh"

#include "astream.hh"
#include "crc.hh"
#include "header.hh"
#include "obuffer.hh"
#include "synthesis_filter.hh"
#include "subband.hh"
#include "subband_layer_1.hh"
#include "scalefactors.hh"


// factors and offsets for sample requantization:
static const real table_factor[15] = {
  0.0, (1.0/2.0) * (4.0/3.0), (1.0/4.0) * (8.0/7.0), (1.0/8.0) * (16.0/15.0),
  (1.0/16.0) * (32.0/31.0), (1.0/32.0) * (64.0/63.0), (1.0/64.0) * (128.0/127.0),
  (1.0/128.0) * (256.0/255.0), (1.0/256.0) * (512.0/511.0),
  (1.0/512.0) * (1024.0/1023.0), (1.0/1024.0) * (2048.0/2047.0),
  (1.0/2048.0) * (4096.0/4095.0), (1.0/4096.0) * (8192.0/8191.0),
  (1.0/8192.0) * (16384.0/16383.0), (1.0/16384.0) * (32768.0/32767.0)
};

static const real table_offset[15] = {
  0.0, ((1.0/2.0)-1.0) * (4.0/3.0), ((1.0/4.0)-1.0) * (8.0/7.0), ((1.0/8.0)-1.0) * (16.0/15.0),
  ((1.0/16.0)-1.0) * (32.0/31.0), ((1.0/32.0)-1.0) * (64.0/63.0), ((1.0/64.0)-1.0) * (128.0/127.0),
  ((1.0/128.0)-1.0) * (256.0/255.0), ((1.0/256.0)-1.0) * (512.0/511.0),
  ((1.0/512.0)-1.0) * (1024.0/1023.0), ((1.0/1024.0)-1.0) * (2048.0/2047.0),
  ((1.0/2048.0)-1.0) * (4096.0/4095.0), ((1.0/4096.0)-1.0) * (8192.0/8191.0),
  ((1.0/8192.0)-1.0) * (16384.0/16383.0), ((1.0/16384.0)-1.0) * (32768.0/32767.0)
};



/**********************/	// used for single channel mode
/*** Standard Class ***/	// and in derived class for intensity
/**********************/	// stereo mode

/* INLINE
SubbandLayer1::SubbandLayer1 (uint32 subbandnumber){
  this->subbandnumber = subbandnumber;
  samplenumber = 0;
}
*/

void SubbandLayer1::read_allocation (AudioStream *stream, Header *, Crc16 *crc){
  if ((allocation = stream->get_bits (4)) == 15)
    cerr << "WARNING: stream contains an illegal allocation!\n";	// MPEG-stream is corrupted!
  if (crc) crc->add_bits (allocation, 4);
  if (allocation){
    samplelength = allocation + 1;
    factor = table_factor[allocation];
    offset = table_offset[allocation];
  }
}


void SubbandLayer1::read_scalefactor (AudioStream *stream, Header *){
  if (allocation)
    if ((scalefactor = stream->get_bits (6)) == 63)
      cerr << "WARNING: stream contains an illegal scalefactor!\n";	// MPEG-stream is corrupted!
}


bool SubbandLayer1::read_sampledata (AudioStream *stream){
  if (allocation){
    sample = real (stream->get_bits (samplelength));
#ifdef DEBUG
    if (sample == (1 << samplelength) - 1)
	cerr << "WARNING: stream contains an illegal subband sample!\n";  // MPEG-stream is corrupted!
#endif
  }
  if (++samplenumber == 12){
    samplenumber = 0;
    return True;
  }
  else return False;
}


bool SubbandLayer1::put_next_sample(e_channels channels,
                                    SynthesisFilter *filter1, SynthesisFilter*){
  if (allocation && channels != right){
    register real scaled_sample = (sample * factor + offset) * scalefactors[scalefactor];
#ifdef DEBUG
    if (scaled_sample < -1.0 || scaled_sample > 1.0)
      cerr << "WARNING: rescaled subband sample is not in [-1.0, 1.0]\n";
      // this should never occur
#endif
    if (scaled_sample < -1.0E-7 || scaled_sample > 1.0E-7)
      filter1->input_sample (scaled_sample, subbandnumber);
  }
  return True;
}


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

/* INLINE
SubbandLayer1IntensityStereo::SubbandLayer1IntensityStereo (uint32 subbandnumber)
: SubbandLayer1 (subbandnumber)
{
}
*/


void SubbandLayer1IntensityStereo::read_scalefactor (AudioStream *stream, Header *)
{
  if (allocation)
  {
    scalefactor = stream->get_bits (6);
    channel2_scalefactor = stream->get_bits (6);
    if (scalefactor == 63 || channel2_scalefactor == 63)
      cerr << "WARNING: stream contains an illegal scalefactor!\n";
      // MPEG-stream is corrupted!
  }
}


bool SubbandLayer1IntensityStereo::put_next_sample (e_channels channels,
	SynthesisFilter *filter1, SynthesisFilter *filter2){
  if (allocation){
    sample = sample * factor + offset;		// requantization
    if (channels == both){
      register real sample1 = sample * scalefactors[scalefactor],
		    sample2 = sample * scalefactors[channel2_scalefactor];
#ifdef DEBUG
      if (sample1 < -1.0 || sample1 > 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 (sample1 < -1.0E-7 || sample1 > 1.0E-7)
	filter1->input_sample (sample1, subbandnumber);
      if (sample2 < -1.0E-7 || sample2 > 1.0E-7)
	filter2->input_sample (sample2, subbandnumber);
    }
    else if (channels == left)
    {
      register real sample1 = sample * scalefactors[scalefactor];
#ifdef DEBUG
      if (sample1 < -1.0 || sample1 > 1.0)
	cerr << "WARNING: rescaled subband sample is not in [-1.0, 1.0]\n";
	// this should never occur
#endif
      if (sample1 < -1.0E-7 || sample1 > 1.0E-7)
	filter1->input_sample (sample1, subbandnumber);
    }
    else
    {
      register real sample2 = sample * scalefactors[channel2_scalefactor];
#ifdef DEBUG
      if (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 (sample2 < -1.0E-7 || sample2 > 1.0E-7)
	filter1->input_sample (sample2, subbandnumber);
    }
  }
  return True;
}



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

/* INLINE
SubbandLayer1Stereo::SubbandLayer1Stereo (uint32 subbandnumber)
: SubbandLayer1 (subbandnumber)
{
}
*/

void SubbandLayer1Stereo::read_allocation (AudioStream *stream, Header *, Crc16 *crc){
  allocation = stream->get_bits (4);
  channel2_allocation = stream->get_bits (4);
  if (crc){
    crc->add_bits (allocation, 4);
    crc->add_bits (channel2_allocation, 4);
  }
  if (allocation == 15 || channel2_allocation == 15)
    cerr << "WARNING: stream contains an illegal allocation!\n";	// MPEG-stream is corrupted!
  if (allocation)
  {
    samplelength = allocation + 1;
    factor = table_factor[allocation];
    offset = table_offset[allocation];
  }
  if (channel2_allocation)
  {
    channel2_samplelength = channel2_allocation + 1;
    channel2_factor = table_factor[channel2_allocation];
    channel2_offset = table_offset[channel2_allocation];
  }
}


void SubbandLayer1Stereo::read_scalefactor (AudioStream *stream, Header *){
  if (allocation)
    if ((scalefactor = stream->get_bits (6)) == 63)
      cerr << "WARNING: stream contains an illegal allocation!\n";	// MPEG-stream is corrupted!
  if (channel2_allocation)
    if ((channel2_scalefactor = stream->get_bits (6)) == 63)
      cerr << "WARNING: stream contains an illegal allocation!\n";	// MPEG-stream is corrupted!
}


bool SubbandLayer1Stereo::read_sampledata (AudioStream *stream){
  bool returnvalue = SubbandLayer1::read_sampledata (stream);
  if (channel2_allocation)
  {
    channel2_sample = real (stream->get_bits (channel2_samplelength));
#ifdef DEBUG
    if (channel2_sample == (1 << channel2_samplelength) - 1)
	cerr << "WARNING: stream contains an illegal subband sample!\n";  // MPEG-stream is corrupted!
#endif
  }
  return returnvalue;
}


bool SubbandLayer1Stereo::put_next_sample (e_channels channels,
					   SynthesisFilter *filter1, SynthesisFilter *filter2)
{
  SubbandLayer1::put_next_sample (channels, filter1, filter2);
  if (channel2_allocation && channels != left)
  {
    register float sample2 = (channel2_sample * channel2_factor + channel2_offset)
			     * scalefactors[channel2_scalefactor];
#ifdef DEBUG
    if (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 (sample2 < -1.0E-7 || sample2 > 1.0E-7)
      if (channels == both)
	filter2->input_sample (sample2, subbandnumber);
      else
	filter1->input_sample (sample2, subbandnumber);
  }
  return True;
}