153 lines
4.3 KiB
C
153 lines
4.3 KiB
C
/*
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* iaxclient: a cross-platform IAX softphone library
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*
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* Copyrights:
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* Copyright (C) 2003-2006, Horizon Wimba, Inc.
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* Copyright (C) 2007, Wimba, Inc.
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*
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* Contributors:
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* Steve Kann <stevek@stevek.com>
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*
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* This program is free software, distributed under the terms of
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* the GNU Lesser (Library) General Public License.
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*/
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#include "codec_ulaw.h"
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#include "iaxclient_lib.h"
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struct state {
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plc_state_t plc;
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};
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static short ulaw_2lin [256];
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static unsigned char lin_2ulaw [16384];
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static int initialized=0;
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/* this looks similar to asterisk, but comes from public domain code by craig reese
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I've just followed asterisk's table sizes for lin_2u, and also too lazy to do binary arith to decide which
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iterations to skip -- this way we get the same result.. */
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static void initialize() {
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int i;
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/* ulaw_2lin */
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for(i=0;i<256;i++) {
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int b = ~i;
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int exp_lut[8] = {0,132,396,924,1980,4092,8316,16764};
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int sign, exponent, mantissa, sample;
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sign = (b & 0x80);
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exponent = (b >> 4) & 0x07;
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mantissa = b & 0x0F;
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sample = exp_lut[exponent] + (mantissa << (exponent + 3));
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if (sign != 0) sample = -sample;
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ulaw_2lin[i] = sample;
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}
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/* lin_2ulaw */
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for(i=-32767;i<32768;i+=4) {
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int sample = i;
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int exp_lut[256] = {0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
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4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
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5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7};
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int sign, exponent, mantissa;
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unsigned char ulawbyte;
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/* Get the sample into sign-magnitude. */
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sign = (sample >> 8) & 0x80; /* set aside the sign */
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if (sign != 0) sample = -sample; /* get magnitude */
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if (sample > 32635) sample = 32635; /* clip the magnitude */
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/* Convert from 16 bit linear to ulaw. */
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sample = sample + 0x84;
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exponent = exp_lut[(sample >> 7) & 0xFF];
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mantissa = (sample >> (exponent + 3)) & 0x0F;
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ulawbyte = ~(sign | (exponent << 4) | mantissa);
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if (ulawbyte == 0) ulawbyte = 0x02; /* optional CCITT trap */
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lin_2ulaw[((unsigned short)i) >> 2] = ulawbyte;
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}
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initialized = 1;
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}
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static void destroy ( struct iaxc_audio_codec *c) {
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if ( c->decstate )
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free(c->decstate);
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free(c);
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}
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static int decode ( struct iaxc_audio_codec *c,
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int *inlen, unsigned char *in, int *outlen, short *out ) {
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struct state *state = (struct state *)c->decstate;
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short *orig_out = out;
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short sample;
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if(*inlen == 0) {
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int interp_len = 160;
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if(*outlen < interp_len) interp_len = *outlen;
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plc_fillin(&state->plc,out,interp_len);
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*outlen -= interp_len;
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return 0;
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}
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while ((*inlen > 0) && (*outlen > 0)) {
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sample = ulaw_2lin[(unsigned char)*(in++)];
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*(out++) = sample;
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(*inlen)--; (*outlen)--;
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}
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plc_rx(&state->plc, orig_out, (int)(out - orig_out));
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return 0;
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}
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static int encode ( struct iaxc_audio_codec *c,
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int *inlen, short *in, int *outlen, unsigned char *out ) {
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while ((*inlen > 0) && (*outlen > 0)) {
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*(out++) = lin_2ulaw[((unsigned short)*(in++)) >> 2];
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(*inlen)--; (*outlen)--;
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}
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return 0;
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}
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struct iaxc_audio_codec *codec_audio_ulaw_new() {
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struct iaxc_audio_codec *c = (struct iaxc_audio_codec *)calloc(sizeof(struct iaxc_audio_codec),1);
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if(!c) return c;
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if(!initialized) initialize();
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strcpy(c->name,"ulaw");
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c->format = IAXC_FORMAT_ULAW;
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c->encode = encode;
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c->decode = decode;
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c->destroy = destroy;
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/* really, we can use less, but don't want to */
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c->minimum_frame_size = 160;
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/* decoder state, used for interpolation */
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c->decstate = calloc(sizeof(struct state),1);
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plc_init(&((struct state *)c->decstate)->plc);
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return c;
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}
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