g726_40.c

sloedgy open sip stack source code

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 * Sun Microsystems, Inc.
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/*
 * g726_40.c
 *
 * Description:
 *
 * g723_40_encoder(), g723_40_decoder()
 *
 * These routines comprise an implementation of the CCITT G.723 40Kbps
 * ADPCM coding algorithm.  Essentially, this implementation is identical to
 * the bit level description except for a few deviations which
 * take advantage of workstation attributes, such as hardware 2's
 * complement arithmetic.
 *
 * The deviation from the bit level specification (lookup tables),
 * preserves the bit level performance specifications.
 *
 * As outlined in the G.723 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_40.c,v $
 * Revision 1.1  2006/06/26 03:02:36  joegenbaclor
 * I have decided to include the latest development realease  of OPAL tagged Deimos Devel 1 (June 8 2006) as inegrated classes to opensipstack to avoid future version conflicts due to the fast pace in OPAL development.   This move is also aimed to reduce the size of projects using OPAL componets such as the soon to be relased OpenSIPPhone.
 *
 * Revision 1.2  2002/11/20 04:53:16  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"

/*
 * Maps G.723_40 code word to ructeconstructed scale factor normalized log
 * magnitude values.
 */
static short	_dqlntab[32] = {-2048, -66, 28, 104, 169, 224, 274, 318,
				358, 395, 429, 459, 488, 514, 539, 566,
				566, 539, 514, 488, 459, 429, 395, 358,
				318, 274, 224, 169, 104, 28, -66, -2048};

/* Maps G.723_40 code word to log of scale factor multiplier. */
static short	_witab[32] = {448, 448, 768, 1248, 1280, 1312, 1856, 3200,
			4512, 5728, 7008, 8960, 11456, 14080, 16928, 22272,
			22272, 16928, 14080, 11456, 8960, 7008, 5728, 4512,
			3200, 1856, 1312, 1280, 1248, 768, 448, 448};

/*
 * Maps G.723_40 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[32] = {0, 0, 0, 0, 0, 0x200, 0x200, 0x200,
			0x200, 0x200, 0x400, 0x600, 0x800, 0xA00, 0xC00, 0xC00,
			0xC00, 0xC00, 0xA00, 0x800, 0x600, 0x400, 0x200, 0x200,
			0x200, 0x200, 0x200, 0, 0, 0, 0, 0};

static int qtab_723_40[15] = {-122, -16, 68, 139, 198, 250, 298, 339,
				378, 413, 445, 475, 502, 528, 553};

/*
 * g723_40_encoder()
 *
 * Encodes a 16-bit linear PCM, A-law or u-law input sample and returns
 * the resulting 5-bit CCITT G.723 40Kbps code.
 * Returns -1 if the input coding value is invalid.
 */
int
g726_40_encoder(
	int		sl,
	int		in_coding,
	g726_state *state_ptr)
{
	int		sezi;
	int		sez;			/* ACCUM */
	int		sei;
	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;		/* sl of 14-bit dynamic range */
		break;
	default:
		return (-1);
	}

	sezi = predictor_zero(state_ptr);
	sez = sezi >> 1;
	sei = sezi + predictor_pole(state_ptr);
	se = sei >> 1;			/* se = estimated signal */

	d = sl - se;			/* d = estimation difference */

	/* quantize prediction difference */
	y = step_size(state_ptr);	/* adaptive quantizer step size */
	i = quantize(d, y, qtab_723_40, 15);	/* i = ADPCM code */

	dq = reconstruct(i & 0x10, _dqlntab[i], y);	/* quantized diff */

	sr = (dq < 0) ? se - (dq & 0x7FFF) : se + dq; /* reconstructed signal */

	dqsez = sr + sez - se;		/* dqsez = pole prediction diff. */

	update(5, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);

	return (i);
}

/*
 * g723_40_decoder()
 *
 * Decodes a 5-bit CCITT G.723 40Kbps code and returns
 * the resulting 16-bit linear PCM, A-law or u-law sample value.
 * -1 is returned if the output coding is unknown.
 */
int
g726_40_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;

	i &= 0x1f;				/* 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);	/* adaptive quantizer step size */
	dq = reconstruct(i & 0x10, _dqlntab[i], y);	/* estimation diff. */

	sr = (dq < 0) ? (se - (dq & 0x7FFF)) : (se + dq); /* reconst. signal */

	dqsez = sr - se + sez;		/* pole prediction diff. */

	update(5, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);

	switch (out_coding) {
	case AUDIO_ENCODING_ALAW:
		return (tandem_adjust_alaw(sr, se, y, i, 0x10, qtab_723_40));
	case AUDIO_ENCODING_ULAW:
		return (tandem_adjust_ulaw(sr, se, y, i, 0x10, qtab_723_40));
	case AUDIO_ENCODING_LINEAR:
		return (sr << 2);	/* sr was of 14-bit dynamic range */
	default:
		return (-1);
	}
}