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Diffstat (limited to 'src/ccitt-adpcm/g721.c')
| -rw-r--r-- | src/ccitt-adpcm/g721.c | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/src/ccitt-adpcm/g721.c b/src/ccitt-adpcm/g721.c new file mode 100644 index 0000000..445f177 --- /dev/null +++ b/src/ccitt-adpcm/g721.c @@ -0,0 +1,173 @@ +/* + * 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 + */ + +/* + * g721.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. + * + */ +#include "g72x.h" + +static short 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 +g721_encoder( + int sl, + int in_coding, + struct g72x_state *state_ptr) +{ + short sezi, se, sez; /* ACCUM */ + short d; /* SUBTA */ + short sr; /* ADDB */ + short y; /* MIX */ + short dqsez; /* ADDC */ + short dq, i; + + 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 +g721_decoder( + int i, + int out_coding, + struct g72x_state *state_ptr) +{ + short sezi, sei, sez, se; /* ACCUM */ + short y; /* MIX */ + short sr; /* ADDB */ + short dq; + short dqsez; + + 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: + return (sr << 2); /* sr was 14-bit dynamic range */ + default: + return (-1); + } +} |