get_audio.c

MPEG-4编解码的实现(包括MPEG4视音频编解码)

  return num_bytes;
}



void CloseSndFile(lame_global_flags *gfp)
{
  if (fclose(musicin) != 0){
    fprintf(stderr, "Could not close audio input file\n");
    exit(2);
  }
}


unsigned long GetSndSamples(void)
{
       return num_samples;
}
int GetSndSampleRate(void)
{
	return samp_freq;
}

int GetSndChannels(void)
{
	return num_channels;
}


FILE * OpenSndFile(lame_global_flags *gfp,const char* inPath, int default_samp,
int default_channels)
{
  struct stat sb;
  void parse_file_header(lame_global_flags *gfp,FILE *sf);
  /* set the defaults from info incase we cannot determine them from file */
  num_samples=MAX_U_32_NUM;
  samp_freq=default_samp;
  num_channels = default_channels;
  
  if (!strcmp(inPath, "-")) {
    /* Read from standard input. */
#ifdef __EMX__
    _fsetmode(stdin,"b");
#elif (defined  __BORLANDC__)
    setmode(_fileno(stdin), O_BINARY);
#elif (defined  __CYGWIN__)
    setmode(fileno(stdin), _O_BINARY);
#elif (defined _WIN32)
    _setmode(_fileno(stdin), _O_BINARY);
#endif
    musicin = stdin;
  } else {
    if ((musicin = fopen(inPath, "rb")) == NULL) {
      fprintf(stderr, "Could not find \"%s\".\n", inPath);
      exit(1);
    }
  }
  
  input_bitrate=0;
  if (gfp->input_format==sf_mp3) {
#ifdef AMIGA_MPEGA
    if (-1==lame_decode_initfile(inPath,&num_channels,&samp_freq,&input_bitrate,&num_samples)) {
      fprintf(stderr,"Error reading headers in mp3 input file %s.\n", inPath);
      exit(1);
    }
#endif
#ifdef HAVEMPGLIB
    if (-1==lame_decode_initfile(musicin,&num_channels,&samp_freq,&input_bitrate,&num_samples)) {
      fprintf(stderr,"Error reading headers in mp3 input file %s.\n", inPath);
      exit(1);
    }
#endif
 }else{
   if (gfp->input_format != sf_raw) {
     parse_file_header(gfp,musicin);
   }
   
   if (gfp->input_format==sf_raw) {
     /* assume raw PCM */
     fprintf(stderr, "Assuming raw pcm input file");
     if (gfp->swapbytes==TRUE)
       fprintf(stderr, " : Forcing byte-swapping\n");
     else
       fprintf(stderr, "\n");
   }
 }
    
  if (num_samples==MAX_U_32_NUM && musicin != stdin) {
    /* try to figure out num_samples */
    if (0==stat(inPath,&sb)) {  
      /* try file size, assume 2 bytes per sample */
      if (gfp->input_format == sf_mp3) {
	FLOAT totalseconds = (sb.st_size*8.0/(1000.0*GetSndBitrate()));
	num_samples= totalseconds*GetSndSampleRate();
      }else{
	num_samples = sb.st_size/(2*GetSndChannels());
      }
    }
  }
  return musicin;
}
  
  
/************************************************************************
*
* read_samples()
*
* PURPOSE:  reads the PCM samples from a file to the buffer
*
*  SEMANTICS:
* Reads #samples_read# number of shorts from #musicin# filepointer
* into #sample_buffer[]#.  Returns the number of samples read.
*
************************************************************************/

int read_samples_pcm(lame_global_flags *gfp,short sample_buffer[2304], int frame_size,int samples_to_read)
{
    int samples_read;
    int rcode;
    int iswav=(gfp->input_format==sf_wave);

    samples_read = fread(sample_buffer, sizeof(short), samples_to_read, musicin);
    if (ferror(musicin)) {
      fprintf(stderr, "Error reading input file\n");
      exit(2);
    }

    /*
       Samples are big-endian. If this is a little-endian machine
       we must swap
     */
    if ( NativeByteOrder == order_unknown )
      {
	NativeByteOrder = DetermineByteOrder();
	if ( NativeByteOrder == order_unknown )
	  {
	    fprintf( stderr, "byte order not determined\n" );
	    exit( 1 );
	  }
      }
    /* intel=littleEndian */
    if (!iswav && ( NativeByteOrder == order_littleEndian ))
      SwapBytesInWords( sample_buffer, samples_read );

    if (iswav && ( NativeByteOrder == order_bigEndian ))
      SwapBytesInWords( sample_buffer, samples_read );

    if (gfp->swapbytes==TRUE)
      SwapBytesInWords( sample_buffer, samples_read );


    rcode=samples_read;
    if (samples_read < frame_size) {
      if (samples_read<0) samples_read=0;
      /*fprintf(stderr,"Insufficient PCM input for one frame - fillout with zeros\n");
      */
      for (; samples_read < frame_size; sample_buffer[samples_read++] = 0);
    }
    return(rcode);
}



#define WAV_ID_RIFF 0x52494646 /* "RIFF" */
#define WAV_ID_WAVE 0x57415645 /* "WAVE" */
#define WAV_ID_FMT  0x666d7420 /* "fmt " */
#define WAV_ID_DATA 0x64617461 /* "data" */

typedef struct fmt_chunk_data_struct {
	short	format_tag;			 /* Format category */
	u_short channels;			 /* Number of channels */
	u_long	samples_per_sec;	 /* Sampling rate */
	u_long	avg_bytes_per_sec;	 /* For buffer estimation */
	u_short block_align;		 /* Data block size */
	u_short bits_per_sample;	 /* for PCM data, anyway... */
} fmt_chunk_data;






/************************************************************************
*
* wave_check
*
* PURPOSE:	Checks Wave header information to make sure it is valid.
*			Exits if not.
*
************************************************************************/

static void
wave_check(char *file_name, fmt_chunk_data *wave_info)
{
	if (wave_info->bits_per_sample != 16) {
		fprintf(stderr, "%d-bit sample-size is not supported!\n",
			wave_info->bits_per_sample);
		exit(1);
	}
}


/*****************************************************************************
 *
 *	Read Microsoft Wave headers
 *
 *	By the time we get here the first 32-bits of the file have already been
 *	read, and we're pretty sure that we're looking at a WAV file.
 *
 *****************************************************************************/

static int
parse_wave_header(FILE *sf)
{
	fmt_chunk_data wave_info;
	int is_wav = 0;
	long data_length = 0, file_length, subSize = 0;
	int loop_sanity = 0;

	memset(&wave_info, 0, sizeof(wave_info));

	file_length = Read32BitsHighLow(sf);

	if (Read32BitsHighLow(sf) != WAV_ID_WAVE)
		return 0;

	for (loop_sanity = 0; loop_sanity < 20; ++loop_sanity) {
		u_int type = Read32BitsHighLow(sf);

		if (type == WAV_ID_FMT) {
			subSize = Read32BitsLowHigh(sf);
			if (subSize < 16) {
			  /*fprintf(stderr,
			    "'fmt' chunk too short (only %ld bytes)!", subSize);  */
				return 0;
			}

			wave_info.format_tag		= Read16BitsLowHigh(sf);
			subSize -= 2;
			wave_info.channels			= Read16BitsLowHigh(sf);
			subSize -= 2;
			wave_info.samples_per_sec	= Read32BitsLowHigh(sf);
			subSize -= 4;
			wave_info.avg_bytes_per_sec = Read32BitsLowHigh(sf);
			subSize -= 4;
			wave_info.block_align		= Read16BitsLowHigh(sf);
			subSize -= 2;
			wave_info.bits_per_sample	= Read16BitsLowHigh(sf);
			subSize -= 2;

			/* fprintf(stderr, "   skipping %d bytes\n", subSize); */

			if (subSize > 0) {
				if (fskip(sf, (long)subSize, SEEK_CUR) != 0 )
					return 0;
			};

		} else if (type == WAV_ID_DATA) {
			subSize = Read32BitsLowHigh(sf);
			data_length = subSize;
			is_wav = 1;
			/* We've found the audio data.	Read no further! */
			break;

		} else {
			subSize = Read32BitsLowHigh(sf);
			if (fskip(sf, (long) subSize, SEEK_CUR) != 0 ) return 0;
		}
	}

	if (is_wav) {
		/* make sure the header is sane */
		wave_check("name", &wave_info);

		num_channels  = wave_info.channels;
		samp_freq     = wave_info.samples_per_sec;
		num_samples   = data_length / (wave_info.channels * wave_info.bits_per_sample / 8);
	}
	return is_wav;
}



/************************************************************************
*
* aiff_check
*
* PURPOSE:	Checks AIFF header information to make sure it is valid.
*			Exits if not.
*
************************************************************************/

static void
aiff_check2(const char *file_name, IFF_AIFF *pcm_aiff_data)
{
	if (pcm_aiff_data->sampleType != IFF_ID_SSND) {
	   fprintf(stderr, "Sound data is not PCM in \"%s\".\n", file_name);
	   exit(1);
	}

	if (pcm_aiff_data->sampleSize != sizeof(short) * BITS_IN_A_BYTE) {
		fprintf(stderr, "Sound data is not %d bits in \"%s\".\n",
				(unsigned int) sizeof(short) * BITS_IN_A_BYTE, file_name);
		exit(1);
	}

	if (pcm_aiff_data->numChannels != 1 &&
		pcm_aiff_data->numChannels != 2) {
	   fprintf(stderr, "Sound data is not mono or stereo in \"%s\".\n",
			   file_name);
	   exit(1);
	}

	if (pcm_aiff_data->blkAlgn.blockSize != 0) {
	   fprintf(stderr, "Block size is not %d bytes in \"%s\".\n",
			   0, file_name);
	   exit(1);
	}

	if (pcm_aiff_data->blkAlgn.offset != 0) {
	   fprintf(stderr, "Block offset is not %d bytes in \"%s\".\n",
			   0, file_name);
	   exit(1);
	}
}

/*****************************************************************************
 *
 *	Read Audio Interchange File Format (AIFF) headers.
 *
 *	By the time we get here the first 32-bits of the file have already been
 *	read, and we're pretty sure that we're looking at an AIFF file.
 *
 *****************************************************************************/

static int
parse_aiff_header(FILE *sf)
{
	int is_aiff = 0;
	long chunkSize = 0, subSize = 0;
	IFF_AIFF aiff_info;

	memset(&aiff_info, 0, sizeof(aiff_info));
	chunkSize = Read32BitsHighLow(sf);
	
	if ( Read32BitsHighLow(sf) != IFF_ID_AIFF )
		return 0;
	
	while ( chunkSize > 0 )
	{
		u_int type = 0;
		chunkSize -= 4;

		type = Read32BitsHighLow(sf);

		/* fprintf(stderr,
			"found chunk type %08x '%4.4s'\n", type, (char*)&type); */

		/* don't use a switch here to make it easier to use 'break' for SSND */
		if (type == IFF_ID_COMM) {
			subSize = Read32BitsHighLow(sf);
			chunkSize -= subSize;

			aiff_info.numChannels	  = Read16BitsHighLow(sf);
			subSize -= 2;
			aiff_info.numSampleFrames = Read32BitsHighLow(sf);
			subSize -= 4;
			aiff_info.sampleSize	  = Read16BitsHighLow(sf);
			subSize -= 2;
			aiff_info.sampleRate	  = ReadIeeeExtendedHighLow(sf);
			subSize -= 10;

			if (fskip(sf, (long) subSize, SEEK_CUR) != 0 )
				return 0;

		} else if (type == IFF_ID_SSND) {
			subSize = Read32BitsHighLow(sf);
			chunkSize -= subSize;

			aiff_info.blkAlgn.offset	= Read32BitsHighLow(sf);
			subSize -= 4;
			aiff_info.blkAlgn.blockSize = Read32BitsHighLow(sf);
			subSize -= 4;

			if (fskip(sf, aiff_info.blkAlgn.offset, SEEK_CUR) != 0 )
				return 0;

			aiff_info.sampleType = IFF_ID_SSND;
			is_aiff = 1;

			/* We've found the audio data.	Read no further! */
			break;
			
		} else {
			subSize = Read32BitsHighLow(sf);
			chunkSize -= subSize;

			if (fskip(sf, (long) subSize, SEEK_CUR) != 0 )
				return 0;
		}
	}

	/* fprintf(stderr, "Parsed AIFF %d\n", is_aiff); */
	if (is_aiff) {
		/* make sure the header is sane */
		aiff_check2("name", &aiff_info);
		num_channels  = aiff_info.numChannels;
		samp_freq     = aiff_info.sampleRate;
		num_samples   = aiff_info.numSampleFrames;
	}
	return is_aiff;
}



/************************************************************************
*
* parse_file_header
*
* PURPOSE: Read the header from a bytestream.  Try to determine whether
*		   it's a WAV file or AIFF without rewinding, since rewind
*		   doesn't work on pipes and there's a good chance we're reading
*		   from stdin (otherwise we'd probably be using libsndfile).
*
* When this function returns, the file offset will be positioned at the
* beginning of the sound data.
*
************************************************************************/

void parse_file_header(lame_global_flags *gfp,FILE *sf)
{
	u_int type = 0;
	type = Read32BitsHighLow(sf);

	/* fprintf(stderr,
		"First word of input stream: %08x '%4.4s'\n", type, (char*) &type); */

	count_samples_carefully=0;
	gfp->input_format = sf_raw;

	if (type == WAV_ID_RIFF) {
		/* It's probably a WAV file */
		if (parse_wave_header(sf)) {
			gfp->input_format = sf_wave;
			count_samples_carefully=1;
		}

	} else if (type == IFF_ID_FORM) {
		/* It's probably an AIFF file */
		if (parse_aiff_header(sf)) {
			gfp->input_format = sf_aiff;
			count_samples_carefully=1;
		}
	}
	if (gfp->input_format==sf_raw) {
	  /*
	  ** Assume it's raw PCM.	 Since the audio data is assumed to begin
	  ** at byte zero, this will unfortunately require seeking.
	  */
	  if (fseek(sf, 0L, SEEK_SET) != 0) {
	    /* ignore errors */
	  }
	  gfp->input_format = sf_raw;
	}
}
#endif  /* LAMESNDFILE */