ac3filesrc.cpp

TMS320C6000 DSP实用技术与开发案例（书号：17481）源程序

#include <stdio.h>
#include <stdlib.h>

#include <windows.h>
#include <vfw.h>

#include "AC3FileSrc.h"

/////////////////////////////

// byte swapping routine
#define SWAP_ENDIAN32(x)  ((((uint_8*)&x)[0] << 24) |  \
			   (((uint_8*)&x)[1] << 16) |  \
			   (((uint_8*)&x)[2] << 8)  |  \
			   ((uint_8*)&x)[3])           

AC3_Bitstream::AC3_Bitstream(FILE *f) 
{
  file            = f;
  current_word    = 0;
  bits_left       = 0;
  total_bits_read = 0;
  done            = FALSE;
  
  // preload data
  this->Load();
}

AC3_Bitstream::~AC3_Bitstream() 
{
}

// Load data from file - does byte swapping
int AC3_Bitstream::Load()
{
  int bytes_read = 0;

  if (file!=NULL){
    bytes_read = fread(&current_word,4,1,file);
  }

  bytes_read = ( bytes_read << 2 ); /* multiply by 4 */

  current_word = SWAP_ENDIAN32(current_word);
  bits_left = bytes_read * 8;

  //FIXME finishing up the stream isn't done too gracefully

  if (bytes_read < 4){  // check to see if end of file
    done = TRUE;
    file = NULL;
  }

  return bytes_read;
}

// Fetches 1-32 bits from the file opened in bitstream_open
int AC3_Bitstream::GetBitSequence(uint_32 num_bits)
{
  uint_32 result;
  uint_32 bits_read;
  uint_32 bits_to_go;

  if(num_bits == 0)
    return 0;

  bits_read = num_bits > bits_left ? bits_left : num_bits; 

  result = current_word  >> (32 - bits_read);
  current_word <<= bits_read;
  bits_left -= bits_read;
  
  if(bits_left == 0){
    long loaded = Load();
  }

  if (bits_read < num_bits) {
    bits_to_go = num_bits - bits_read;
    result <<= bits_to_go;
    result |= current_word  >> (32 - bits_to_go);
    current_word <<= bits_to_go;
    bits_left -= bits_to_go;
  }
	
  total_bits_read += num_bits;
  // crc_process(result,num_bits);

  return result;
}


// Positions the stream pointer to a sync word
int AC3_Bitstream::Resync() {

  int i = 0;
  uint_16 sync_word;

  if (!file) return -1;

  sync_word = GetBitSequence(16);

  /* Make sure we sync'ed */
  while(1) {
    if(sync_word == 0x0b77)
      break;
    sync_word = ( sync_word << 1 );
    sync_word |= GetBitSequence(1);
    i++;
    if (i > 32) {  // fix added to handle EOF or closed files 
                   // printf( "EOF %d\n", ftell( bs->file ) );
      if ( ftell(file)==-1 || feof(file) ) {
	i = -1;
	break;
      }
    }
  }

  total_bits_read = 16;
  // crc_init();

  return i; /* return # bits skipped */
}

///////////////////////////

const uint_16 nfchans[] = {2,1,2,3,3,4,4,5};

struct frmsize_s
{
  uint_16 bit_rate;
  uint_16 frm_size[3];
};

const struct frmsize_s frmsizecod_tbl[] = {
      { 32  ,{64   ,69   ,96   } },
      { 32  ,{64   ,70   ,96   } },
      { 40  ,{80   ,87   ,120  } },
      { 40  ,{80   ,88   ,120  } },
      { 48  ,{96   ,104  ,144  } },
      { 48  ,{96   ,105  ,144  } },
      { 56  ,{112  ,121  ,168  } },
      { 56  ,{112  ,122  ,168  } },
      { 64  ,{128  ,139  ,192  } },
      { 64  ,{128  ,140  ,192  } },
      { 80  ,{160  ,174  ,240  } },
      { 80  ,{160  ,175  ,240  } },
      { 96  ,{192  ,208  ,288  } },
      { 96  ,{192  ,209  ,288  } },
      { 112 ,{224  ,243  ,336  } },
      { 112 ,{224  ,244  ,336  } },
      { 128 ,{256  ,278  ,384  } },
      { 128 ,{256  ,279  ,384  } },
      { 160 ,{320  ,348  ,480  } },
      { 160 ,{320  ,349  ,480  } },
      { 192 ,{384  ,417  ,576  } },
      { 192 ,{384  ,418  ,576  } },
      { 224 ,{448  ,487  ,672  } },
      { 224 ,{448  ,488  ,672  } },
      { 256 ,{512  ,557  ,768  } },
      { 256 ,{512  ,558  ,768  } },
      { 320 ,{640  ,696  ,960  } },
      { 320 ,{640  ,697  ,960  } },
      { 384 ,{768  ,835  ,1152 } },
      { 384 ,{768  ,836  ,1152 } },
      { 448 ,{896  ,975  ,1344 } },
      { 448 ,{896  ,976  ,1344 } },
      { 512 ,{1024 ,1114 ,1536 } },
      { 512 ,{1024 ,1115 ,1536 } },
      { 576 ,{1152 ,1253 ,1728 } },
      { 576 ,{1152 ,1254 ,1728 } },
      { 640 ,{1280 ,1393 ,1920 } },
      { 640 ,{1280 ,1394 ,1920 } }
};

AC3FileSrc::AC3FileSrc(FILE *ac3File) 
{
  // set the file ptr
  m_ac3File = ac3File;
}

AC3FileSrc::~AC3FileSrc() 
{
  // nothing
}

BOOL AC3FileSrc::Parse(LPWAVEFORMATEX fmt)
{
  if (m_ac3File==NULL) {
    return FALSE;
  }

  // create a bitstream
  m_ac3Bitstream = new AC3_Bitstream(m_ac3File);

  // sync to the start of an AC3 frame
  if (m_ac3Bitstream->Resync() < 0) {
    // unable to resync - clean up and return
    delete m_ac3Bitstream;
    return FALSE;
  }

  // create sync info structure
  m_sync_info = new AC3_SYNCINFO();

  // and parse the sync_info
  ParseSyncInfo();

  // create the BSI
  m_bsi = new AC3_BSI();
  ParseBSI();

  fmt->wFormatTag = WAVE_FORMAT_DOLBY_AC3;
  fmt->nChannels  = m_bsi->nfchans;

  switch (m_sync_info->fscod) {
  case 2:
    fmt->nSamplesPerSec = 32000;
    break;
  case 1:
    fmt->nSamplesPerSec = 44100;
    break;
  case 0:
    fmt->nSamplesPerSec = 48000;
    break;
  default:
    fmt->nSamplesPerSec = 0;
    break;
  }

  fmt->nAvgBytesPerSec = (1000 * m_sync_info->bit_rate) / 8;
  fmt->nBlockAlign = 1;
  fmt->wBitsPerSample = 0;
  fmt->cbSize = sizeof(WAVEFORMATEX);

  delete m_bsi;
  delete m_sync_info;
  delete m_ac3Bitstream;

  return TRUE;
}

// Parse a syncinfo structure, minus the sync word
void AC3FileSrc::ParseSyncInfo()
{
  /* Get crc1 - we don't actually use this data though */
  m_ac3Bitstream->GetBitSequence(16);
  
  /* Get the sampling rate */
  m_sync_info->fscod  = m_ac3Bitstream->GetBitSequence(2);
  
  /* Get the frame size code */
  m_sync_info->frmsizecod = m_ac3Bitstream->GetBitSequence(6);
  
  m_sync_info->bit_rate = frmsizecod_tbl[m_sync_info->frmsizecod].bit_rate;
  m_sync_info->frame_size = frmsizecod_tbl[m_sync_info->frmsizecod].frm_size[m_sync_info->fscod];

  // stats_printf_syncinfo(syncinfo);
}

void AC3FileSrc::ParseBSI()
{
  uint_32 i;

  /* Check the AC-3 version number */
  m_bsi->bsid = m_ac3Bitstream->GetBitSequence(5);

  /* Get the audio service provided by the steram */
  m_bsi->bsmod = m_ac3Bitstream->GetBitSequence(3);

  /* Get the audio coding mode (ie how many channels)*/
  m_bsi->acmod = m_ac3Bitstream->GetBitSequence(3);
  /* Predecode the number of full bandwidth channels as we use this
   * number a lot */
  m_bsi->nfchans = nfchans[m_bsi->acmod];

  /* If it is in use, get the centre channel mix level */
  if ((m_bsi->acmod & 0x1) && (m_bsi->acmod != 0x1))
    m_bsi->cmixlev = m_ac3Bitstream->GetBitSequence(2);

  /* If it is in use, get the surround channel mix level */
  if (m_bsi->acmod & 0x4)
    m_bsi->surmixlev = m_ac3Bitstream->GetBitSequence(2);

  /* Get the dolby surround mode if in 2/0 mode */
  if(m_bsi->acmod == 0x2)
    m_bsi->dsurmod= m_ac3Bitstream->GetBitSequence(2);

  /* Is the low frequency effects channel on? */
  m_bsi->lfeon = m_ac3Bitstream->GetBitSequence(1);

  /* Get the dialogue normalization level */
  m_bsi->dialnorm = m_ac3Bitstream->GetBitSequence(5);

  /* Does compression gain exist? */
  m_bsi->compre = m_ac3Bitstream->GetBitSequence(1);
  if (m_bsi->compre) {
    /* Get compression gain */
    m_bsi->compr = m_ac3Bitstream->GetBitSequence(8);
  }

  /* Does language code exist? */
  m_bsi->langcode = m_ac3Bitstream->GetBitSequence(1);
  if (m_bsi->langcode) {
    /* Get langauge code */
    m_bsi->langcod = m_ac3Bitstream->GetBitSequence(8);
  }

  /* Does audio production info exist? */
  m_bsi->audprodie = m_ac3Bitstream->GetBitSequence(1);
  if (m_bsi->audprodie) {
    /* Get mix level */
    m_bsi->mixlevel = m_ac3Bitstream->GetBitSequence(5);
    
    /* Get room type */
    m_bsi->roomtyp = m_ac3Bitstream->GetBitSequence(2);
  }

  /* If we're in dual mono mode then get some extra info */
  if (m_bsi->acmod ==0) {
    /* Get the dialogue normalization level two */
    m_bsi->dialnorm2 = m_ac3Bitstream->GetBitSequence(5);

    /* Does compression gain two exist? */
    m_bsi->compr2e = m_ac3Bitstream->GetBitSequence(1);
    if (m_bsi->compr2e) {
      /* Get compression gain two */
      m_bsi->compr2 = m_ac3Bitstream->GetBitSequence(8);
    }

    /* Does language code two exist? */
    m_bsi->langcod2e = m_ac3Bitstream->GetBitSequence(1);
    if (m_bsi->langcod2e) {
      /* Get langauge code two */
      m_bsi->langcod2 = m_ac3Bitstream->GetBitSequence(8);
    }

    /* Does audio production info two exist? */
    m_bsi->audprodi2e = m_ac3Bitstream->GetBitSequence(1);
    if (m_bsi->audprodi2e) {
      /* Get mix level two */
      m_bsi->mixlevel2 = m_ac3Bitstream->GetBitSequence(5);

      /* Get room type two */
      m_bsi->roomtyp2 = m_ac3Bitstream->GetBitSequence(2);
    }
  }

  /* Get the copyright bit */
  m_bsi->copyrightb = m_ac3Bitstream->GetBitSequence(1);

  /* Get the original bit */
  m_bsi->origbs = m_ac3Bitstream->GetBitSequence(1);
	
  /* Does timecode one exist? */
  m_bsi->timecod1e = m_ac3Bitstream->GetBitSequence(1);

  if(m_bsi->timecod1e) {
    m_bsi->timecod1 = m_ac3Bitstream->GetBitSequence(14);
  }

  /* Does timecode two exist? */
  m_bsi->timecod2e = m_ac3Bitstream->GetBitSequence(1);

  if(m_bsi->timecod2e) {
    m_bsi->timecod2 = m_ac3Bitstream->GetBitSequence(14);
  }
  /* Does addition info exist? */
  m_bsi->addbsie = m_ac3Bitstream->GetBitSequence(1);

  if(m_bsi->addbsie) {
    /* Get how much info is there */
    m_bsi->addbsil = m_ac3Bitstream->GetBitSequence(6);
    
    /* Get the additional info */
    for(i=0;i<(m_bsi->addbsil + 1);i++)
      m_bsi->addbsi[i] = m_ac3Bitstream->GetBitSequence(8);
  }
  // stats_printf_bsi(bsi);
}