123 lines
4.1 KiB
C
Executable File
123 lines
4.1 KiB
C
Executable File
/*
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* This source code is a product of Sun Microsystems, Inc. and is provided
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* for unrestricted use. Users may copy or modify this source code without
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* charge.
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*
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* SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
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* THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
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*
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* Sun source code is provided with no support and without any obligation on
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* the part of Sun Microsystems, Inc. to assist in its use, correction,
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* modification or enhancement.
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*
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* SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
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* INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
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* OR ANY PART THEREOF.
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*
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* In no event will Sun Microsystems, Inc. be liable for any lost revenue
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* or profits or other special, indirect and consequential damages, even if
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* Sun has been advised of the possibility of such damages.
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*
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* Sun Microsystems, Inc.
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* 2550 Garcia Avenue
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* Mountain View, California 94043
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*/
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/*
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* g726_24.c
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*
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* Description:
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*
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* g723_24_encoder(), g723_24_decoder()
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*
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* These routines comprise an implementation of the CCITT G.723 24 Kbps
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* ADPCM coding algorithm. Essentially, this implementation is identical to
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* the bit level description except for a few deviations which take advantage
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* of workstation attributes, such as hardware 2's complement arithmetic.
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*
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* The ITU-T G.726 coder is an adaptive differential pulse code modulation
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* (ADPCM) waveform coding algorithm, suitable for coding of digitized
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* telephone bandwidth (0.3-3.4 kHz) speech or audio signals sampled at 8 kHz.
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* This coder operates on a sample-by-sample basis. Input samples may be
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* represented in linear PCM or companded 8-bit G.711 (m-law/A-law) formats
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* (i.e., 64 kbps). For 32 kbps operation, each sample is converted into a
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* 4-bit quantized difference signal resulting in a compression ratio of
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* 2:1 over the G.711 format. For 24 kbps 40 kbps operation, the quantized
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* difference signal is 3 bits and 5 bits, respectively.
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*
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* $Log: g726_24.c,v $
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* Revision 1.4 2002/11/20 04:29:13 robertj
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* Included optimisations for G.711 and G.726 codecs, thanks Ted Szoczei
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*
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* Revision 1.1 2002/02/11 23:24:23 robertj
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* Updated to openH323 v1.8.0
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*
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* Revision 1.2 2002/02/10 21:14:54 dereks
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* Add cvs log history to head of the file.
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* Ensure file is terminated by a newline.
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*
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*
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*
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*/
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#include "g72x.h"
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#include "private.h"
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/*
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* Maps G.723_24 code word to reconstructed scale factor normalized log
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* magnitude values.
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*/
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static const short _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048};
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/* Maps G.723_24 code word to log of scale factor multiplier. */
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static const short _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128};
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/*
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* Maps G.723_24 code words to a set of values whose long and short
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* term averages are computed and then compared to give an indication
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* how stationary (steady state) the signal is.
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*/
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static const short _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0};
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//static int qtab_723_24[3] = {8, 218, 331};
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/*
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* g723_24_decoder()
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*
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* Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
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* the resulting 16-bit linear PCM, A-law or u-law sample value.
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* -1 is returned if the output coding is unknown.
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*/
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int
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g726_24_decoder(
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int i,
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g726_state *state_ptr)
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{
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int sezi;
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int sez; /* ACCUM */
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int sei;
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int se;
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int y; /* MIX */
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int dq;
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int sr; /* ADDB */
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int dqsez;
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i &= 0x07; /* mask to get proper bits */
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sezi = predictor_zero(state_ptr);
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sez = sezi >> 1;
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sei = sezi + predictor_pole(state_ptr);
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se = sei >> 1; /* se = estimated signal */
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y = step_size(state_ptr); /* adaptive quantizer step size */
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dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
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sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
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dqsez = sr - se + sez; /* pole prediction diff. */
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update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
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return (sr << 2); /* sr was of 14-bit dynamic range */
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}
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