www.pudn.com > g.726.rar > g726_32.c, change:2002-11-20,size:6691b


/* 
 * This source code is a product of Sun Microsystems, Inc. and is provided 
 * for unrestricted use.  Users may copy or modify this source code without 
 * charge. 
 * 
 * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING 
 * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR 
 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. 
 * 
 * Sun source code is provided with no support and without any obligation on 
 * the part of Sun Microsystems, Inc. to assist in its use, correction, 
 * modification or enhancement. 
 * 
 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE 
 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE 
 * OR ANY PART THEREOF. 
 * 
 * In no event will Sun Microsystems, Inc. be liable for any lost revenue 
 * or profits or other special, indirect and consequential damages, even if 
 * Sun has been advised of the possibility of such damages. 
 * 
 * Sun Microsystems, Inc. 
 * 2550 Garcia Avenue 
 * Mountain View, California  94043 
 */ 
 
/* 
 * g726_32.c 
 * 
 * Description: 
 * 
 * g721_encoder(), g721_decoder() 
 * 
 * These routines comprise an implementation of the CCITT G.721 ADPCM 
 * coding algorithm.  Essentially, this implementation is identical to 
 * the bit level description except for a few deviations which 
 * take advantage of work station attributes, such as hardware 2's 
 * complement arithmetic and large memory.  Specifically, certain time 
 * consuming operations such as multiplications are replaced 
 * with lookup tables and software 2's complement operations are 
 * replaced with hardware 2's complement. 
 * 
 * The deviation from the bit level specification (lookup tables) 
 * preserves the bit level performance specifications. 
 * 
 * As outlined in the G.721 Recommendation, the algorithm is broken 
 * down into modules.  Each section of code below is preceded by 
 * the name of the module which it is implementing. 
 * 
 * The ITU-T G.726 coder is an adaptive differential pulse code modulation 
 * (ADPCM) waveform coding algorithm, suitable for coding of digitized 
 * telephone bandwidth (0.3-3.4 kHz) speech or audio signals sampled at 8 kHz. 
 * This coder operates on a sample-by-sample basis. Input samples may be  
 * represented in linear PCM or companded 8-bit G.711 (m-law/A-law) formats 
 * (i.e., 64 kbps). For 32 kbps operation, each sample is converted into a 
 * 4-bit quantized difference signal resulting in a compression ratio of  
 * 2:1 over the G.711 format. For 24 kbps 40 kbps operation, the quantized 
 * difference signal is 3 bits and 5 bits, respectively. 
 * 
 * $Log: g726_32.c,v $ 
 * Revision 1.5  2002/11/20 04:29:13  robertj 
 * Included optimisations for G.711 and G.726 codecs, thanks Ted Szoczei 
 * 
 * Revision 1.1  2002/02/11 23:24:23  robertj 
 * Updated to openH323 v1.8.0 
 * 
 * Revision 1.2  2002/02/10 21:14:54  dereks 
 * Add cvs log history to head of the file. 
 * Ensure file is terminated by a newline. 
 * 
 * 
 * 
 */ 
#include "g72x.h" 
#include "private.h" 
 
static int qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400}; 
/* 
 * Maps G.721 code word to reconstructed scale factor normalized log 
 * magnitude values. 
 */ 
static short	_dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425, 
				425, 373, 323, 273, 213, 135, 4, -2048}; 
 
/* Maps G.721 code word to log of scale factor multiplier. */ 
static short	_witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122, 
				1122, 355, 198, 112, 64, 41, 18, -12}; 
/* 
 * Maps G.721 code words to a set of values whose long and short 
 * term averages are computed and then compared to give an indication 
 * how stationary (steady state) the signal is. 
 */ 
static short	_fitab[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00, 
				0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0}; 
 
/* 
 * g721_encoder() 
 * 
 * Encodes the input vale of linear PCM, A-law or u-law data sl and returns 
 * the resulting code. -1 is returned for unknown input coding value. 
 */ 
int 
g726_32_encoder( 
	int		sl, 
	int		in_coding, 
	g726_state *state_ptr) 
{ 
	int		sezi; 
	int		sez;			/* ACCUM */ 
	int		se; 
	int		d;				/* SUBTA */ 
	int		y;				/* MIX */ 
	int		i; 
	int		dq; 
	int		sr;				/* ADDB */ 
	int		dqsez;			/* ADDC */ 
 
	switch (in_coding) {	/* linearize input sample to 14-bit PCM */ 
	case AUDIO_ENCODING_ALAW: 
		sl = alaw2linear(sl) >> 2; 
		break; 
	case AUDIO_ENCODING_ULAW: 
		sl = ulaw2linear(sl) >> 2; 
		break; 
	case AUDIO_ENCODING_LINEAR: 
		sl >>= 2;			/* 14-bit dynamic range */ 
		break; 
	default: 
		return (-1); 
	} 
 
	sezi = predictor_zero(state_ptr); 
	sez = sezi >> 1; 
	se = (sezi + predictor_pole(state_ptr)) >> 1;	/* estimated signal */ 
 
	d = sl - se;				/* estimation difference */ 
 
	/* quantize the prediction difference */ 
	y = step_size(state_ptr);		/* quantizer step size */ 
	i = quantize(d, y, qtab_721, 7);	/* i = ADPCM code */ 
 
	dq = reconstruct(i & 8, _dqlntab[i], y);	/* quantized est diff */ 
 
	sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq;	/* reconst. signal */ 
 
	dqsez = sr + sez - se;			/* pole prediction diff. */ 
 
	update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr); 
 
	return (i); 
} 
 
/* 
 * g721_decoder() 
 * 
 * Description: 
 * 
 * Decodes a 4-bit code of G.721 encoded data of i and 
 * returns the resulting linear PCM, A-law or u-law value. 
 * return -1 for unknown out_coding value. 
 */ 
int 
g726_32_decoder( 
	int		i, 
	int		out_coding, 
	g726_state *state_ptr) 
{ 
	int		sezi; 
	int		sez;			/* ACCUM */ 
	int		sei; 
	int		se; 
	int		y;				/* MIX */ 
	int		dq; 
	int		sr;				/* ADDB */ 
	int		dqsez; 
	long	lino; 
 
	i &= 0x0f;				/* mask to get proper bits */ 
	sezi = predictor_zero(state_ptr); 
	sez = sezi >> 1; 
	sei = sezi + predictor_pole(state_ptr); 
	se = sei >> 1;			/* se = estimated signal */ 
 
	y = step_size(state_ptr);	/* dynamic quantizer step size */ 
 
	dq = reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */ 
 
	sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq;	/* reconst. signal */ 
 
	dqsez = sr - se + sez;			/* pole prediction diff. */ 
 
	update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr); 
 
	switch (out_coding) { 
	case AUDIO_ENCODING_ALAW: 
		return (tandem_adjust_alaw(sr, se, y, i, 8, qtab_721)); 
	case AUDIO_ENCODING_ULAW: 
		return (tandem_adjust_ulaw(sr, se, y, i, 8, qtab_721)); 
	case AUDIO_ENCODING_LINEAR: 
        lino = (long)sr << 2;  /* this seems to overflow a short*/ 
		lino = lino > 32767 ? 32767 : lino; 
		lino = lino < -32768 ? -32768 : lino; 
		return lino;//(sr << 2);	/* sr was 14-bit dynamic range */ 
	default: 
		return (-1); 
	} 
}