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/project/jni/sndfile/src/G72x/g721.c

https://github.com/aichunyu/FFPlayer
C | 155 lines | 55 code | 23 blank | 77 comment | 0 complexity | bf846c15c5a48a6709f0b0285a007520 MD5 | raw file
  1/*
  2 * This source code is a product of Sun Microsystems, Inc. and is provided
  3 * for unrestricted use.  Users may copy or modify this source code without
  4 * charge.
  5 *
  6 * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
  7 * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
  8 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
  9 *
 10 * Sun source code is provided with no support and without any obligation on
 11 * the part of Sun Microsystems, Inc. to assist in its use, correction,
 12 * modification or enhancement.
 13 *
 14 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
 15 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
 16 * OR ANY PART THEREOF.
 17 *
 18 * In no event will Sun Microsystems, Inc. be liable for any lost revenue
 19 * or profits or other special, indirect and consequential damages, even if
 20 * Sun has been advised of the possibility of such damages.
 21 *
 22 * Sun Microsystems, Inc.
 23 * 2550 Garcia Avenue
 24 * Mountain View, California  94043
 25 */
 26
 27/*
 28 * g721.c
 29 *
 30 * Description:
 31 *
 32 * g721_encoder(), g721_decoder()
 33 *
 34 * These routines comprise an implementation of the CCITT G.721 ADPCM
 35 * coding algorithm.  Essentially, this implementation is identical to
 36 * the bit level description except for a few deviations which
 37 * take advantage of work station attributes, such as hardware 2's
 38 * complement arithmetic and large memory.  Specifically, certain time
 39 * consuming operations such as multiplications are replaced
 40 * with lookup tables and software 2's complement operations are
 41 * replaced with hardware 2's complement.
 42 *
 43 * The deviation from the bit level specification (lookup tables)
 44 * preserves the bit level performance specifications.
 45 *
 46 * As outlined in the G.721 Recommendation, the algorithm is broken
 47 * down into modules.  Each section of code below is preceded by
 48 * the name of the module which it is implementing.
 49 *
 50 */
 51
 52#include "g72x.h"
 53#include "g72x_priv.h"
 54
 55static short qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400};
 56/*
 57 * Maps G.721 code word to reconstructed scale factor normalized log
 58 * magnitude values.
 59 */
 60static short	_dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425,
 61				425, 373, 323, 273, 213, 135, 4, -2048};
 62
 63/* Maps G.721 code word to log of scale factor multiplier. */
 64static short	_witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122,
 65				1122, 355, 198, 112, 64, 41, 18, -12};
 66/*
 67 * Maps G.721 code words to a set of values whose long and short
 68 * term averages are computed and then compared to give an indication
 69 * how stationary (steady state) the signal is.
 70 */
 71static short	_fitab[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
 72				0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};
 73
 74/*
 75 * g721_encoder()
 76 *
 77 * Encodes the input vale of linear PCM, A-law or u-law data sl and returns
 78 * the resulting code. -1 is returned for unknown input coding value.
 79 */
 80int
 81g721_encoder(
 82	int		sl,
 83	G72x_STATE *state_ptr)
 84{
 85	short		sezi, se, sez;		/* ACCUM */
 86	short		d;			/* SUBTA */
 87	short		sr;			/* ADDB */
 88	short		y;			/* MIX */
 89	short		dqsez;			/* ADDC */
 90	short		dq, i;
 91
 92	/* linearize input sample to 14-bit PCM */
 93	sl >>= 2;			/* 14-bit dynamic range */
 94
 95	sezi = predictor_zero(state_ptr);
 96	sez = sezi >> 1;
 97	se = (sezi + predictor_pole(state_ptr)) >> 1;	/* estimated signal */
 98
 99	d = sl - se;				/* estimation difference */
100
101	/* quantize the prediction difference */
102	y = step_size(state_ptr);		/* quantizer step size */
103	i = quantize(d, y, qtab_721, 7);	/* i = ADPCM code */
104
105	dq = reconstruct(i & 8, _dqlntab[i], y);	/* quantized est diff */
106
107	sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq;	/* reconst. signal */
108
109	dqsez = sr + sez - se;			/* pole prediction diff. */
110
111	update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
112
113	return (i);
114}
115
116/*
117 * g721_decoder()
118 *
119 * Description:
120 *
121 * Decodes a 4-bit code of G.721 encoded data of i and
122 * returns the resulting linear PCM, A-law or u-law value.
123 * return -1 for unknown out_coding value.
124 */
125int
126g721_decoder(
127	int		i,
128	G72x_STATE *state_ptr)
129{
130	short		sezi, sei, sez, se;	/* ACCUM */
131	short		y;			/* MIX */
132	short		sr;			/* ADDB */
133	short		dq;
134	short		dqsez;
135
136	i &= 0x0f;			/* mask to get proper bits */
137	sezi = predictor_zero(state_ptr);
138	sez = sezi >> 1;
139	sei = sezi + predictor_pole(state_ptr);
140	se = sei >> 1;			/* se = estimated signal */
141
142	y = step_size(state_ptr);	/* dynamic quantizer step size */
143
144	dq = reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */
145
146	sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq;	/* reconst. signal */
147
148	dqsez = sr - se + sez;			/* pole prediction diff. */
149
150	update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
151
152	/* sr was 14-bit dynamic range */
153	return (sr << 2);	
154}
155