360 lines
7.7 KiB
C
360 lines
7.7 KiB
C
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/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Based on frompcm.c and topcm.c from the Emiliano MIPL browser/
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* interpreter. See http://www.bsdtelephony.com.mx
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*
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* Copyright (c) 2001 - 2005 Digium, Inc.
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* All rights reserved.
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*
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* Karl Sackett <krs@linux-support.net>, 2001-03-21
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief codec_adpcm.c - translate between signed linear and Dialogic ADPCM
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*
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* \ingroup codecs
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*/
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/*** MODULEINFO
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<support_level>core</support_level>
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***/
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#include "asterisk.h"
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#include "asterisk/lock.h"
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#include "asterisk/linkedlists.h"
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#include "asterisk/module.h"
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#include "asterisk/config.h"
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#include "asterisk/translate.h"
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#include "asterisk/utils.h"
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/* define NOT_BLI to use a faster but not bit-level identical version */
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/* #define NOT_BLI */
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#define BUFFER_SAMPLES 8096 /* size for the translation buffers */
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/* Sample frame data */
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#include "asterisk/slin.h"
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#include "ex_adpcm.h"
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/*
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* Step size index shift table
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*/
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static int indsft[8] = { -1, -1, -1, -1, 2, 4, 6, 8 };
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/*
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* Step size table, where stpsz[i]=floor[16*(11/10)^i]
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*/
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static int stpsz[49] = {
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16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45, 50, 55, 60, 66, 73,
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80, 88, 97, 107, 118, 130, 143, 157, 173, 190, 209, 230, 253, 279,
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307, 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, 876, 963,
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1060, 1166, 1282, 1411, 1552
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};
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/*
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* Decoder/Encoder state
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* States for both encoder and decoder are synchronized
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*/
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struct adpcm_state {
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int ssindex;
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int signal;
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int zero_count;
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int next_flag;
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};
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/*
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* Decode(encoded)
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* Decodes the encoded nibble from the adpcm file.
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*
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* Results:
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* Returns the encoded difference.
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*
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* Side effects:
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* Sets the index to the step size table for the next encode.
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*/
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static inline short decode(int encoded, struct adpcm_state *state)
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{
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int diff;
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int step;
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int sign;
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step = stpsz[state->ssindex];
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sign = encoded & 0x08;
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encoded &= 0x07;
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#ifdef NOT_BLI
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diff = (((encoded << 1) + 1) * step) >> 3;
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#else /* BLI code */
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diff = step >> 3;
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if (encoded & 4)
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diff += step;
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if (encoded & 2)
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diff += step >> 1;
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if (encoded & 1)
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diff += step >> 2;
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if ((encoded >> 1) & step & 0x1)
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diff++;
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#endif
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if (sign)
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diff = -diff;
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if (state->next_flag & 0x1)
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state->signal -= 8;
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else if (state->next_flag & 0x2)
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state->signal += 8;
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state->signal += diff;
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if (state->signal > 2047)
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state->signal = 2047;
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else if (state->signal < -2047)
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state->signal = -2047;
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state->next_flag = 0;
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#ifdef AUTO_RETURN
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if (encoded)
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state->zero_count = 0;
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else if (++(state->zero_count) == 24) {
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state->zero_count = 0;
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if (state->signal > 0)
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state->next_flag = 0x1;
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else if (state->signal < 0)
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state->next_flag = 0x2;
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}
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#endif
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state->ssindex += indsft[encoded];
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if (state->ssindex < 0)
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state->ssindex = 0;
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else if (state->ssindex > 48)
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state->ssindex = 48;
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return state->signal << 4;
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}
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/*
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* Adpcm
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* Takes a signed linear signal and encodes it as ADPCM
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* For more information see http://en.wikipedia.org/wiki/Dialogic_ADPCM
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*
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* Results:
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* Foo.
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*
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* Side effects:
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* signal gets updated with each pass.
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*/
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static inline int adpcm(short csig, struct adpcm_state *state)
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{
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int diff;
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int step;
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int encoded;
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/*
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* Clip csig if too large or too small
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*/
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csig >>= 4;
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step = stpsz[state->ssindex];
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diff = csig - state->signal;
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#ifdef NOT_BLI
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if (diff < 0) {
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encoded = (-diff << 2) / step;
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if (encoded > 7)
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encoded = 7;
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encoded |= 0x08;
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} else {
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encoded = (diff << 2) / step;
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if (encoded > 7)
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encoded = 7;
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}
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#else /* BLI code */
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if (diff < 0) {
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encoded = 8;
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diff = -diff;
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} else
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encoded = 0;
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if (diff >= step) {
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encoded |= 4;
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diff -= step;
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}
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step >>= 1;
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if (diff >= step) {
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encoded |= 2;
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diff -= step;
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}
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step >>= 1;
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if (diff >= step)
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encoded |= 1;
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#endif /* NOT_BLI */
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/* feedback to state */
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decode(encoded, state);
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return encoded;
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}
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/*----------------- Asterisk-codec glue ------------*/
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/*! \brief Workspace for translating signed linear signals to ADPCM. */
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struct adpcm_encoder_pvt {
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struct adpcm_state state;
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int16_t inbuf[BUFFER_SAMPLES]; /* Unencoded signed linear values */
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};
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/*! \brief Workspace for translating ADPCM signals to signed linear. */
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struct adpcm_decoder_pvt {
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struct adpcm_state state;
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};
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/*! \brief decode 4-bit adpcm frame data and store in output buffer */
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static int adpcmtolin_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
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{
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struct adpcm_decoder_pvt *tmp = pvt->pvt;
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int x = f->datalen;
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unsigned char *src = f->data.ptr;
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int16_t *dst = pvt->outbuf.i16 + pvt->samples;
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while (x--) {
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*dst++ = decode((*src >> 4) & 0xf, &tmp->state);
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*dst++ = decode(*src++ & 0x0f, &tmp->state);
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}
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pvt->samples += f->samples;
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pvt->datalen += 2*f->samples;
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return 0;
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}
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/*! \brief fill input buffer with 16-bit signed linear PCM values. */
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static int lintoadpcm_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
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{
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struct adpcm_encoder_pvt *tmp = pvt->pvt;
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memcpy(&tmp->inbuf[pvt->samples], f->data.ptr, f->datalen);
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pvt->samples += f->samples;
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return 0;
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}
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/*! \brief convert inbuf and store into frame */
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static struct ast_frame *lintoadpcm_frameout(struct ast_trans_pvt *pvt)
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{
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struct adpcm_encoder_pvt *tmp = pvt->pvt;
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struct ast_frame *f;
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int i;
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int samples = pvt->samples; /* save original number */
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if (samples < 2)
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return NULL;
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pvt->samples &= ~1; /* atomic size is 2 samples */
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for (i = 0; i < pvt->samples; i += 2) {
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pvt->outbuf.c[i/2] =
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(adpcm(tmp->inbuf[i ], &tmp->state) << 4) |
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(adpcm(tmp->inbuf[i+1], &tmp->state) );
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};
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f = ast_trans_frameout(pvt, pvt->samples/2, 0);
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/*
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* If there is a left over sample, move it to the beginning
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* of the input buffer.
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*/
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if (samples & 1) { /* move the leftover sample at beginning */
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tmp->inbuf[0] = tmp->inbuf[samples - 1];
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pvt->samples = 1;
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}
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return f;
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}
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static struct ast_translator adpcmtolin = {
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.name = "adpcmtolin",
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.src_codec = {
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.name = "adpcm",
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.type = AST_MEDIA_TYPE_AUDIO,
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.sample_rate = 8000,
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},
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.dst_codec = {
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.name = "slin",
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.type = AST_MEDIA_TYPE_AUDIO,
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.sample_rate = 8000,
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},
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.format = "slin",
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.framein = adpcmtolin_framein,
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.sample = adpcm_sample,
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.desc_size = sizeof(struct adpcm_decoder_pvt),
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.buffer_samples = BUFFER_SAMPLES,
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.buf_size = BUFFER_SAMPLES * 2,
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};
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static struct ast_translator lintoadpcm = {
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.name = "lintoadpcm",
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.src_codec = {
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.name = "slin",
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.type = AST_MEDIA_TYPE_AUDIO,
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.sample_rate = 8000,
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},
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.dst_codec = {
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.name = "adpcm",
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.type = AST_MEDIA_TYPE_AUDIO,
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.sample_rate = 8000,
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},
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.format = "adpcm",
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.framein = lintoadpcm_framein,
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.frameout = lintoadpcm_frameout,
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.sample = slin8_sample,
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.desc_size = sizeof (struct adpcm_encoder_pvt),
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.buffer_samples = BUFFER_SAMPLES,
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.buf_size = BUFFER_SAMPLES/ 2, /* 2 samples per byte */
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};
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static int unload_module(void)
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{
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int res;
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res = ast_unregister_translator(&lintoadpcm);
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res |= ast_unregister_translator(&adpcmtolin);
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return res;
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}
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static int load_module(void)
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{
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int res = 0;
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res = ast_register_translator(&adpcmtolin);
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res |= ast_register_translator(&lintoadpcm);
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if (res) {
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unload_module();
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return AST_MODULE_LOAD_DECLINE;
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}
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return AST_MODULE_LOAD_SUCCESS;
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}
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AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "Adaptive Differential PCM Coder/Decoder",
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.support_level = AST_MODULE_SUPPORT_CORE,
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.load = load_module,
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.unload = unload_module,
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);
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