alaw_test.c

Audacity是一款用於錄音和編輯聲音的、免費的開放源碼軟體。它可以執行於Mac OS X、Microsoft Windows、GNU/Linux和其它作業系統

/*
** Copyright (C) 1999-2004 Erik de Castro Lopo <[e-mail]>
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

#include "config.h"

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

#if HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <sndfile.h>

#include "utils.h"

#define	BUFFER_SIZE		(65536)

static unsigned char	alaw_encode (int sample) ;
static int				alaw_decode (unsigned int alawbyte) ;

static	short			short_buffer [BUFFER_SIZE] ;
static	unsigned char	alaw_buffer [BUFFER_SIZE] ;

int
main (void)
{	SNDFILE		*file ;
	SF_INFO		sfinfo ;
	const char	*filename ;
	int			k ;

	filename = "test.raw" ;

	sfinfo.format		= SF_FORMAT_RAW | SF_FORMAT_ALAW ;
	sfinfo.samplerate	= 44100 ;
	sfinfo.frames		= 123456789 ; /* Wrong length. Library should correct this on sf_close. */
	sfinfo.channels		= 1 ;

	if ((file = sf_open (filename, SFM_WRITE, &sfinfo)) == NULL)
	{	printf ("sf_open_write failed with error : ") ;
		fflush (stdout) ;
		puts (sf_strerror (NULL)) ;
		exit (1) ;
		} ;

	/* Generate a file containing all possible 16 bit sample values
	** and write it to disk as alaw encoded.frames.
	*/

	for (k = 0 ; k < 0x10000 ; k++)
		short_buffer [k] = k & 0xFFFF ;

	sf_write_short (file, short_buffer, BUFFER_SIZE) ;
	sf_close (file) ;

	/* Now open that file and compare the alaw encoded sample values
	** with what they should be.
	*/

	if ((file = sf_open (filename, SFM_READ, &sfinfo)) == NULL)
	{	printf ("sf_open_write failed with error : ") ;
		puts (sf_strerror (NULL)) ;
		exit (1) ;
		} ;

	check_log_buffer_or_die (file, __LINE__) ;

	if (sf_read_raw (file, alaw_buffer, BUFFER_SIZE) != BUFFER_SIZE)
	{	printf ("sf_read_raw : ") ;
		puts (sf_strerror (file)) ;
		exit (1) ;
		} ;

	for (k = 0 ; k < 0x10000 ; k++)
		if (alaw_encode (short_buffer [k]) != alaw_buffer [k])
		{	printf ("Encoder error : sample #%d (0x%02X should be 0x%02X)\n", k, alaw_buffer [k], alaw_encode (short_buffer [k])) ;
			exit (1) ;
			} ;

	sf_close (file) ;

	printf ("    alaw_test : encoder ... ok\n") ;

	/* Now generate a file containing all possible 8 bit encoded
	** sample values and write it to disk as alaw encoded.frames.
	*/

	if (! (file = sf_open (filename, SFM_WRITE, &sfinfo)))
	{	printf ("sf_open_write failed with error : ") ;
		puts (sf_strerror (NULL)) ;
		exit (1) ;
		} ;

	for (k = 0 ; k < 256 ; k++)
		alaw_buffer [k] = k & 0xFF ;

	sf_write_raw (file, alaw_buffer, 256) ;
	sf_close (file) ;

	/* Now open that file and compare the alaw decoded sample values
	** with what they should be.
	*/

	if (! (file = sf_open (filename, SFM_READ, &sfinfo)))
	{	printf ("sf_open_write failed with error : ") ;
		puts (sf_strerror (NULL)) ;
		exit (1) ;
		} ;

	check_log_buffer_or_die (file, __LINE__) ;

	if (sf_read_short (file, short_buffer, 256) != 256)
	{	printf ("sf_read_short : ") ;
		puts (sf_strerror (file)) ;
		exit (1) ;
		} ;


	for (k = 0 ; k < 256 ; k++)
		if (short_buffer [k] != alaw_decode (alaw_buffer [k]))
		{	printf ("Decoder error : sample #%d (0x%02X should be 0x%02X)\n", k, short_buffer [k], alaw_decode (alaw_buffer [k])) ;
			exit (1) ;
			} ;

	sf_close (file) ;

	printf ("    alaw_test : decoder ... ok\n") ;

	unlink (filename) ;

	return 0 ;
} /* main */


/*=================================================================================
**	The following routines came from the sox-12.15 (Sound eXcahcnge) distribution.
**
**	This code is not compiled into libsndfile. It is only used to test the
**	libsndfile lookup tables for correctness.
**
**	I have included the original authors comments.
*/

/*
** A-law routines by Graeme W. Gill.
** Date: 93/5/7
**
** References:
** 1) CCITT Recommendation G.711
**
*/

#define ACLIP 31744

static
unsigned char alaw_encode (int sample)
{	static int exp_lut [128] =
	{	1, 1, 2, 2, 3, 3, 3, 3,
		4, 4, 4, 4, 4, 4, 4, 4,
		5, 5, 5, 5, 5, 5, 5, 5,
		5, 5, 5, 5, 5, 5, 5, 5,
		6, 6, 6, 6, 6, 6, 6, 6,
		6, 6, 6, 6, 6, 6, 6, 6,
		6, 6, 6, 6, 6, 6, 6, 6,
		6, 6, 6, 6, 6, 6, 6, 6,
		7, 7, 7, 7, 7, 7, 7, 7,
		7, 7, 7, 7, 7, 7, 7, 7,
		7, 7, 7, 7, 7, 7, 7, 7,
		7, 7, 7, 7, 7, 7, 7, 7,
		7, 7, 7, 7, 7, 7, 7, 7,
		7, 7, 7, 7, 7, 7, 7, 7,
		7, 7, 7, 7, 7, 7, 7, 7,
		7, 7, 7, 7, 7, 7, 7, 7
		} ;

    int sign, exponent, mantissa ;
    unsigned char Alawbyte ;

    /* Get the sample into sign-magnitude. */
    sign = ((~sample) >> 8) & 0x80 ;			/* set aside the sign */
    if (sign == 0)
		sample = -sample ;		/* get magnitude */
    if (sample > ACLIP)
		sample = ACLIP ;						/* clip the magnitude */

    /* Convert from 16 bit linear to ulaw. */
    if (sample >= 256)
	{	exponent = exp_lut [(sample >> 8) & 0x7F] ;
		mantissa = ( sample >> ( exponent + 3 ) ) & 0x0F ;
		Alawbyte = ((exponent << 4) | mantissa) ;
		}
    else
		Alawbyte = (sample >> 4) ;

	Alawbyte ^= (sign ^ 0x55) ;

    return Alawbyte ;
} /* alaw_encode */

static
int alaw_decode (unsigned int Alawbyte)
{	static int exp_lut [8] = { 0, 264, 528, 1056, 2112, 4224, 8448, 16896 } ;
    int sign, exponent, mantissa, sample ;

    Alawbyte ^= 0x55 ;
    sign = (Alawbyte & 0x80) ;
    Alawbyte &= 0x7f ;			/* get magnitude */
    if (Alawbyte >= 16)
	{	exponent = (Alawbyte >> 4 ) & 0x07 ;
		mantissa = Alawbyte & 0x0F ;
		sample = exp_lut [exponent] + (mantissa << ( exponent + 3 )) ;
		}
    else
		sample = (Alawbyte << 4) + 8 ;
    if (sign == 0)
		sample = -sample ;

    return sample ;
} /* alaw_decode */









/*
** Do not edit or modify anything in this comment block.
** The arch-tag line is a file identity tag for the GNU Arch 
** revision control system.
**
** arch-tag: d3fb5eae-b3a4-4c5b-90ab-e3daa64c4a57
*/