159 lines
3.1 KiB
C
159 lines
3.1 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) 2004 Cyril VELTER
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*
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* Contributors:
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* Cyril VELTER <cyril.velter@metadys.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_alaw.h"
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#include "iaxclient_lib.h"
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#if defined(_MSC_VER)
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#define INLINE __inline
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#else
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#define INLINE inline
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#endif
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struct state {
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plc_state_t plc;
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};
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static INLINE short int alawdecode (unsigned char alaw)
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{
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int value;
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int segment;
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/* Mask value */
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alaw ^= 0x55;
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/* Extract and scale value */
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value = (alaw & 0x0f) << 4;
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/* Extract segment number */
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segment = (alaw & 0x70) >> 4;
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/* Compute value */
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switch (segment) {
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case 0:
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break;
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case 1:
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value += 0x100;
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break;
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default:
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value += 0x100;
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value <<= segment - 1;
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}
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/* Extract sign */
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return (alaw & 0x80) ? value : -value;
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}
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static INLINE unsigned char alawencode (short int linear)
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{
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int mask = 0x55;
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int segment;
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unsigned char alaw;
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static int segments[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};
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if (linear >= 0)
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{
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/* Sign (7th) bit = 1 */
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mask |= 0x80;
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}
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else
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{
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/* Sign (7th) bit = 0 */
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linear = -linear;
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}
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/* Find the segment */
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for (segment = 0;segment < 8;segment++)
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if (linear <= segments[segment])
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break;
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/* Combine the sign, segment, and quantization bits. */
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if (segment < 8)
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{
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if (segment < 2)
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alaw = (linear >> 4) & 0x0F;
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else
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alaw = (linear >> (segment + 3)) & 0x0F;
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return ((alaw | (segment << 4)) ^ mask);
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}
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else
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/* out of range, return maximum value. */
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return (0x7F ^ mask);
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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 = alawdecode((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++) = alawencode(*(in++));
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(*inlen)--; (*outlen)--;
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}
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return 0;
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}
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static void destroy ( struct iaxc_audio_codec *c) {
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free(c);
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}
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struct iaxc_audio_codec *codec_audio_alaw_new() {
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struct iaxc_audio_codec *c = (struct iaxc_audio_codec *)calloc(1, sizeof(struct iaxc_audio_codec));
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if(!c) return c;
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strcpy(c->name,"alaw");
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c->format = IAXC_FORMAT_ALAW;
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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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