au.c

SIP（Session Initiation Protocol）是由IETF定义

		return error ;

	if (! psf->sf.samples && psf->blockwidth)
		psf->sf.samples = au_fmt.datasize / psf->blockwidth ;


	return 0 ;
} /* au_open_read */

/*------------------------------------------------------------------------------
*/

int
au_nh_open_read	(SF_PRIVATE *psf)
{	if (fseek (psf->file, psf->dataoffset, SEEK_SET))
		return SFE_BAD_SEEK ;

	psf_log_printf (psf, "Headers-less u-law encoded file.\n") ;
	psf_log_printf (psf, "Setting up for 8kHz, mono, u-law.\n") ;
	
	psf->sf.format = SF_FORMAT_AU | SF_FORMAT_ULAW ;

 	psf->dataoffset = 0 ;
 	psf->current  = 0 ;
	psf->endian   = 0 ;  /* Irrelevant but it must be something. */
	psf->sf.seekable = SF_TRUE ;
	psf->sf.samplerate	= 8000 ;
	psf->sf.channels 	= 1 ;
	psf->sf.sections 	= 1 ;
	psf->sf.pcmbitwidth = 16 ;	/* After decoding */
	psf->bytewidth   	= 1 ;	/* Before decoding */
					
	ulaw_read_init (psf) ;
	
	psf->close 	     = (func_close)  au_close ;

	psf->blockwidth = 1 ;
	psf->sf.samples = psf->filelength ;
	psf->datalength = psf->filelength - AU_DATA_OFFSET ;

	return 0 ;
} /* au_open_read */

/*------------------------------------------------------------------------------
*/

int
au_open_write	(SF_PRIVATE *psf)
{	unsigned int	encoding, format, subformat ;
	int				error = 0 ;

	format = psf->sf.format & SF_FORMAT_TYPEMASK ;
	subformat = psf->sf.format & SF_FORMAT_SUBMASK ;
	if (format == SF_FORMAT_AU)
		psf->endian = SF_ENDIAN_BIG ;
	else if (format == SF_FORMAT_AULE)
		psf->endian = SF_ENDIAN_LITTLE ;
	else
		return	SFE_BAD_OPEN_FORMAT ;
		
	if (subformat == SF_FORMAT_ULAW || subformat == SF_FORMAT_ALAW || 
		subformat == SF_FORMAT_G721_32 || subformat == SF_FORMAT_G723_24)
		psf->bytewidth = 1 ;
	else
		psf->bytewidth = BITWIDTH2BYTES (psf->sf.pcmbitwidth) ;
		
	psf->sf.seekable = SF_TRUE ;
	psf->error       = 0 ;

	psf->blockwidth  = psf->bytewidth * psf->sf.channels ;
 	psf->dataoffset  = AU_DATA_OFFSET ;
	psf->datalength  = psf->blockwidth * psf->sf.samples ;
	psf->filelength  = psf->datalength + psf->dataoffset ;

	if (! (encoding = au_write_header (psf)))
		return psf->error ;

	psf->close        = (func_close)  au_close ;
	psf->write_header = (func_wr_hdr) au_write_header ;
	
	switch (encoding)
	{	case  AU_ENCODING_ULAW_8 :	/* 8-bit Ulaw encoding. */
				ulaw_write_init (psf) ;
				break ;
	
		case  AU_ENCODING_PCM_8 :	/* 8-bit linear PCM. */
				psf->chars = SF_CHARS_SIGNED ;

				error = pcm_write_init (psf) ;				
				break ;

		case  AU_ENCODING_PCM_16 :	/* 16-bit linear PCM. */
		case  AU_ENCODING_PCM_24 :	/* 24-bit linear PCM */
		case  AU_ENCODING_PCM_32 :	/* 32-bit linear PCM. */
				error = pcm_write_init (psf) ;
				break ;
				
		case  AU_ENCODING_ALAW_8 :	/* 8-bit Alaw encoding. */
				alaw_write_init (psf) ;
				break ;
	
		case  AU_ENCODING_ADPCM_G721_32 :  
				if (psf->sf.channels != 1)
				{	psf_log_printf (psf, "Channels != 1\n") ;
					break ;
					} ;
				psf->sf.pcmbitwidth = 16 ;	/* After decoding */
				psf->bytewidth   	= 0 ;
				psf->blockwidth = psf->sf.channels * psf->bytewidth ;
				
				psf->sf.format |= SF_FORMAT_G721_32 ;
				
				error = au_g72x_writer_init (psf, AU_H_G721_32) ;
				break ;

		case  AU_ENCODING_ADPCM_G723_24 :  
				if (psf->sf.channels != 1)
				{	psf_log_printf (psf, "Channels != 1\n") ;
					break ;
					} ;
				psf->sf.pcmbitwidth = 16 ;	/* After decoding */
				psf->bytewidth   	= 0 ;
				psf->blockwidth = psf->sf.channels * psf->bytewidth ;
				
				psf->sf.format |= SF_FORMAT_G721_32 ;
				
				error = au_g72x_writer_init (psf, AU_H_G723_24) ;
				break ;

		default :   break ;
		} ;
		
	return error ;
} /* au_open_write */

/*------------------------------------------------------------------------------
*/

static int
au_close	(SF_PRIVATE  *psf)
{
	if (psf->mode == SF_MODE_WRITE)
	{	/*  Now we know for certain the length of the file we can
		 *  re-write correct values for the datasize header element.
		 */

		fseek (psf->file, 0, SEEK_END) ;
		psf->filelength = ftell (psf->file) ;

		psf->datalength = psf->filelength - AU_DATA_OFFSET ;
		fseek (psf->file, 0, SEEK_SET) ;
		
		psf->sf.samples = psf->datalength / psf->blockwidth ;
		au_write_header (psf) ;
		} ;

	if (psf->fdata)
		free (psf->fdata) ;
	psf->fdata = NULL ;
	
	return 0 ;
} /* au_close */

static int
au_write_header (SF_PRIVATE *psf)
{	int		encoding ;

	encoding = get_encoding (psf->sf.format & SF_FORMAT_SUBMASK, psf->bytewidth * 8) ;
	if (! encoding)
	{	psf->error = SFE_BAD_OPEN_FORMAT ;
		return	encoding ;
		} ;

	/* Reset the current header length to zero. */
	psf->header [0] = 0 ;
	psf->headindex = 0 ;
	fseek (psf->file, 0, SEEK_SET) ;

	if (psf->endian == SF_ENDIAN_BIG)
	{	psf_binheader_writef (psf, "mL", DOTSND_MARKER, AU_DATA_OFFSET) ;
		psf_binheader_writef (psf, "LLLL", psf->datalength, encoding, psf->sf.samplerate, psf->sf.channels) ;
		}
	else if  (psf->endian == SF_ENDIAN_LITTLE)
	{	psf_binheader_writef (psf, "ml", DNSDOT_MARKER, AU_DATA_OFFSET) ;
		psf_binheader_writef (psf, "llll", psf->datalength, encoding, psf->sf.samplerate, psf->sf.channels) ;
		}
	else
	{	psf->error = SFE_BAD_OPEN_FORMAT ;
		return	encoding ;
		} ;

	/* Header cunstruction complete so write it out. */
	fwrite (psf->header, psf->headindex, 1, psf->file) ;

	psf->dataoffset = psf->headindex ;
	
	return encoding ;
} /* au_write_header */ 

static int
get_encoding (unsigned int format, unsigned int	bitwidth)
{	if (format == SF_FORMAT_ULAW)
		return AU_ENCODING_ULAW_8 ;
		
	if (format == SF_FORMAT_ALAW)
		return AU_ENCODING_ALAW_8 ;

	if (format == SF_FORMAT_G721_32)
		return AU_ENCODING_ADPCM_G721_32 ;

	if (format == SF_FORMAT_G723_24)
		return AU_ENCODING_ADPCM_G723_24 ;

	if (format != SF_FORMAT_PCM)
		return 0 ;

	/* For PCM encoding, the header encoding field depends on the bitwidth. */
	switch (bitwidth)
	{	case	8  : return AU_ENCODING_PCM_8 ;
		case	16 : return AU_ENCODING_PCM_16 ;
		case	24 : return AU_ENCODING_PCM_24 ;
		case	32 : return	AU_ENCODING_PCM_32 ;
		default : break ;
		} ;
	return 0 ;
} /* get_encoding */

/*-
static void
endswap_au_fmt (AU_FMT *pau_fmt)
{	pau_fmt->dataoffset = ENDSWAP_INT (pau_fmt->dataoffset) ;
	pau_fmt->datasize   = ENDSWAP_INT (pau_fmt->datasize) ;
	pau_fmt->encoding   = ENDSWAP_INT (pau_fmt->encoding) ;
    pau_fmt->samplerate = ENDSWAP_INT (pau_fmt->samplerate) ;
    pau_fmt->channels   = ENDSWAP_INT (pau_fmt->channels) ;
} /+* endswap_au_fmt *+/
-*/

static	char const* 
get_encoding_str (int format)
{	switch (format)
	{	case  AU_ENCODING_ULAW_8 :	
				return "8-bit ISDN u-law" ;
										
		case  AU_ENCODING_PCM_8 :	
				return "8-bit linear PCM" ;

		case  AU_ENCODING_PCM_16 :	
				return "16-bit linear PCM" ;

		case  AU_ENCODING_PCM_24 :	
				return "24-bit linear PCM" ;

		case  AU_ENCODING_PCM_32 :	
				return "32-bit linear PCM" ;
					
		case  AU_ENCODING_ALAW_8 :
				return "8-bit ISDN A-law" ;
					
		case  AU_ENCODING_ADPCM_G721_32 :  
				return "G721 32kbs ADPCM" ;
										
		case  AU_ENCODING_ADPCM_G723_24 :  
				return "G723 24kbs ADPCM" ;
										
		case  AU_ENCODING_NEXT :	
				return "Weird NeXT encoding format (unsupported)" ;
		} ;
	return "Unknown!!" ;
} /* get_encoding_str */