asterisk/codecs/codec_adpcm.c

360 lines
7.7 KiB
C

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