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FFmpeg/libavcodec/g726.c

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/*
* G.726 ADPCM audio codec
* Copyright (c) 2004 Roman Shaposhnik.
*
* This is a very straightforward rendition of the G.726
* Section 4 "Computational Details".
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <limits.h>
#include "avcodec.h"
#include "bitstream.h"
/**
* G.726 11bit float.
* G.726 Standard uses rather odd 11bit floating point arithmentic for
* numerous occasions. It's a mistery to me why they did it this way
* instead of simply using 32bit integer arithmetic.
*/
typedef struct Float11 {
int sign; /**< 1bit sign */
int exp; /**< 4bit exponent */
int mant; /**< 6bit mantissa */
} Float11;
static inline Float11* i2f(int16_t i, Float11* f)
{
f->sign = (i < 0);
if (f->sign)
i = -i;
f->exp = av_log2_16bit(i) + !!i;
f->mant = i? (i<<6) >> f->exp : 1<<5;
return f;
}
static inline int16_t mult(Float11* f1, Float11* f2)
{
int res, exp;
exp = f1->exp + f2->exp;
res = (((f1->mant * f2->mant) + 0x30) >> 4) << 7;
res = exp > 26 ? res << (exp - 26) : res >> (26 - exp);
return (f1->sign ^ f2->sign) ? -res : res;
}
static inline int sgn(int value)
{
return (value < 0) ? -1 : 1;
}
typedef struct G726Tables {
int bits; /**< bits per sample */
const int* quant; /**< quantization table */
const int* iquant; /**< inverse quantization table */
const int* W; /**< special table #1 ;-) */
const int* F; /**< special table #2 */
} G726Tables;
typedef struct G726Context {
const G726Tables* tbls; /**< static tables needed for computation */
Float11 sr[2]; /**< prev. reconstructed samples */
Float11 dq[6]; /**< prev. difference */
int a[2]; /**< second order predictor coeffs */
int b[6]; /**< sixth order predictor coeffs */
int pk[2]; /**< signs of prev. 2 sez + dq */
int ap; /**< scale factor control */
int yu; /**< fast scale factor */
int yl; /**< slow scale factor */
int dms; /**< short average magnitude of F[i] */
int dml; /**< long average magnitude of F[i] */
int td; /**< tone detect */
int se; /**< estimated signal for the next iteration */
int sez; /**< estimated second order prediction */
int y; /**< quantizer scaling factor for the next iteration */
} G726Context;
static const int quant_tbl16[] = /**< 16kbit/s 2bits per sample */
{ 260, INT_MAX };
static const int iquant_tbl16[] =
{ 116, 365, 365, 116 };
static const int W_tbl16[] =
{ -22, 439, 439, -22 };
static const int F_tbl16[] =
{ 0, 7, 7, 0 };
static const int quant_tbl24[] = /**< 24kbit/s 3bits per sample */
{ 7, 217, 330, INT_MAX };
static const int iquant_tbl24[] =
{ INT_MIN, 135, 273, 373, 373, 273, 135, INT_MIN };
static const int W_tbl24[] =
{ -4, 30, 137, 582, 582, 137, 30, -4 };
static const int F_tbl24[] =
{ 0, 1, 2, 7, 7, 2, 1, 0 };
static const int quant_tbl32[] = /**< 32kbit/s 4bits per sample */
{ -125, 79, 177, 245, 299, 348, 399, INT_MAX };
static const int iquant_tbl32[] =
{ INT_MIN, 4, 135, 213, 273, 323, 373, 425,
425, 373, 323, 273, 213, 135, 4, INT_MIN };
static const int W_tbl32[] =
{ -12, 18, 41, 64, 112, 198, 355, 1122,
1122, 355, 198, 112, 64, 41, 18, -12};
static const int F_tbl32[] =
{ 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
static const int quant_tbl40[] = /**< 40kbit/s 5bits per sample */
{ -122, -16, 67, 138, 197, 249, 297, 338,
377, 412, 444, 474, 501, 527, 552, INT_MAX };
static const int iquant_tbl40[] =
{ INT_MIN, -66, 28, 104, 169, 224, 274, 318,
358, 395, 429, 459, 488, 514, 539, 566,
566, 539, 514, 488, 459, 429, 395, 358,
318, 274, 224, 169, 104, 28, -66, INT_MIN };
static const int W_tbl40[] =
{ 14, 14, 24, 39, 40, 41, 58, 100,
141, 179, 219, 280, 358, 440, 529, 696,
696, 529, 440, 358, 280, 219, 179, 141,
100, 58, 41, 40, 39, 24, 14, 14 };
static const int F_tbl40[] =
{ 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
static const G726Tables G726Tables_pool[] =
{{ 2, quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 },
{ 3, quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 },
{ 4, quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
{ 5, quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};
/**
* Para 4.2.2 page 18: Adaptive quantizer.
*/
static inline uint8_t quant(G726Context* c, int d)
{
int sign, exp, i, dln;
sign = i = 0;
if (d < 0) {
sign = 1;
d = -d;
}
exp = av_log2_16bit(d);
dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
while (c->tbls->quant[i] < INT_MAX && c->tbls->quant[i] < dln)
++i;
if (sign)
i = ~i;
if (c->tbls->bits != 2 && i == 0) /* I'm not sure this is a good idea */
i = 0xff;
return i;
}
/**
* Para 4.2.3 page 22: Inverse adaptive quantizer.
*/
static inline int16_t inverse_quant(G726Context* c, int i)
{
int dql, dex, dqt;
dql = c->tbls->iquant[i] + (c->y >> 2);
dex = (dql>>7) & 0xf; /* 4bit exponent */
dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
return (dql < 0) ? 0 : ((dqt<<7) >> (14-dex));
}
static inline int16_t g726_iterate(G726Context* c, int16_t I)
{
int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
Float11 f;
dq = inverse_quant(c, I);
if (I >> (c->tbls->bits - 1)) /* get the sign */
dq = -dq;
re_signal = c->se + dq;
/* Transition detect */
ylint = (c->yl >> 15);
ylfrac = (c->yl >> 10) & 0x1f;
thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
if (c->td == 1 && abs(dq) > ((thr2+(thr2>>1))>>1))
tr = 1;
else
tr = 0;
/* Update second order predictor coefficient A2 and A1 */
pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
dq0 = dq ? sgn(dq) : 0;
if (tr) {
c->a[0] = 0;
c->a[1] = 0;
for (i=0; i<6; i++)
c->b[i] = 0;
} else {
/* This is a bit crazy, but it really is +255 not +256 */
fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
c->a[1] = av_clip(c->a[1], -12288, 12288);
c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
for (i=0; i<6; i++)
c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
}
/* Update Dq and Sr and Pk */
c->pk[1] = c->pk[0];
c->pk[0] = pk0 ? pk0 : 1;
c->sr[1] = c->sr[0];
i2f(re_signal, &c->sr[0]);
for (i=5; i>0; i--)
c->dq[i] = c->dq[i-1];
i2f(dq, &c->dq[0]);
c->dq[0].sign = I >> (c->tbls->bits - 1); /* Isn't it crazy ?!?! */
/* Update tone detect [I'm not sure 'tr == 0' is really needed] */
c->td = (tr == 0 && c->a[1] < -11776);
/* Update Ap */
c->dms += ((c->tbls->F[I]<<9) - c->dms) >> 5;
c->dml += ((c->tbls->F[I]<<11) - c->dml) >> 7;
if (tr)
c->ap = 256;
else if (c->y > 1535 && !c->td && (abs((c->dms << 2) - c->dml) < (c->dml >> 3)))
c->ap += (-c->ap) >> 4;
else
c->ap += (0x200 - c->ap) >> 4;
/* Update Yu and Yl */
c->yu = av_clip(c->y + (((c->tbls->W[I] << 5) - c->y) >> 5), 544, 5120);
c->yl += c->yu + ((-c->yl)>>6);
/* Next iteration for Y */
al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
/* Next iteration for SE and SEZ */
c->se = 0;
for (i=0; i<6; i++)
c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
c->sez = c->se >> 1;
for (i=0; i<2; i++)
c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
c->se >>= 1;
return av_clip(re_signal << 2, -0xffff, 0xffff);
}
static int g726_reset(G726Context* c, int bit_rate)
{
int i;
c->tbls = &G726Tables_pool[bit_rate/8000 - 2];
for (i=0; i<2; i++) {
i2f(0, &c->sr[i]);
c->a[i] = 0;
c->pk[i] = 1;
}
for (i=0; i<6; i++) {
i2f(0, &c->dq[i]);
c->b[i] = 0;
}
c->ap = 0;
c->dms = 0;
c->dml = 0;
c->yu = 544;
c->yl = 34816;
c->td = 0;
c->se = 0;
c->sez = 0;
c->y = 544;
return 0;
}
static int16_t g726_decode(G726Context* c, int16_t i)
{
return g726_iterate(c, i);
}
#ifdef CONFIG_ENCODERS
static int16_t g726_encode(G726Context* c, int16_t sig)
{
uint8_t i;
i = quant(c, sig/4 - c->se) & ((1<<c->tbls->bits) - 1);
g726_iterate(c, i);
return i;
}
#endif
/* Interfacing to the libavcodec */
typedef struct AVG726Context {
G726Context c;
int bits_left;
int bit_buffer;
int code_size;
} AVG726Context;
static int g726_init(AVCodecContext * avctx)
{
AVG726Context* c = (AVG726Context*)avctx->priv_data;
if (avctx->channels != 1 ||
(avctx->bit_rate != 16000 && avctx->bit_rate != 24000 &&
avctx->bit_rate != 32000 && avctx->bit_rate != 40000)) {
av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
return -1;
}
if (avctx->sample_rate != 8000 && avctx->strict_std_compliance>FF_COMPLIANCE_INOFFICIAL) {
av_log(avctx, AV_LOG_ERROR, "G726: unsupported audio format\n");
return -1;
}
g726_reset(&c->c, avctx->bit_rate);
c->code_size = c->c.tbls->bits;
c->bit_buffer = 0;
c->bits_left = 0;
avctx->coded_frame = avcodec_alloc_frame();
if (!avctx->coded_frame)
return AVERROR(ENOMEM);
avctx->coded_frame->key_frame = 1;
return 0;
}
static int g726_close(AVCodecContext *avctx)
{
av_freep(&avctx->coded_frame);
return 0;
}
#ifdef CONFIG_ENCODERS
static int g726_encode_frame(AVCodecContext *avctx,
uint8_t *dst, int buf_size, void *data)
{
AVG726Context *c = avctx->priv_data;
short *samples = data;
PutBitContext pb;
init_put_bits(&pb, dst, 1024*1024);
for (; buf_size; buf_size--)
put_bits(&pb, c->code_size, g726_encode(&c->c, *samples++));
flush_put_bits(&pb);
return put_bits_count(&pb)>>3;
}
#endif
static int g726_decode_frame(AVCodecContext *avctx,
void *data, int *data_size,
uint8_t *buf, int buf_size)
{
AVG726Context *c = avctx->priv_data;
short *samples = data;
uint8_t code;
uint8_t mask;
GetBitContext gb;
if (!buf_size)
goto out;
mask = (1<<c->code_size) - 1;
init_get_bits(&gb, buf, buf_size * 8);
if (c->bits_left) {
int s = c->code_size - c->bits_left;;
code = (c->bit_buffer << s) | get_bits(&gb, s);
*samples++ = g726_decode(&c->c, code & mask);
}
while (get_bits_count(&gb) + c->code_size <= buf_size*8)
*samples++ = g726_decode(&c->c, get_bits(&gb, c->code_size) & mask);
c->bits_left = buf_size*8 - get_bits_count(&gb);
c->bit_buffer = get_bits(&gb, c->bits_left);
out:
*data_size = (uint8_t*)samples - (uint8_t*)data;
return buf_size;
}
#ifdef CONFIG_ENCODERS
AVCodec adpcm_g726_encoder = {
"g726",
CODEC_TYPE_AUDIO,
CODEC_ID_ADPCM_G726,
sizeof(AVG726Context),
g726_init,
g726_encode_frame,
g726_close,
NULL,
};
#endif //CONFIG_ENCODERS
AVCodec adpcm_g726_decoder = {
"g726",
CODEC_TYPE_AUDIO,
CODEC_ID_ADPCM_G726,
sizeof(AVG726Context),
g726_init,
NULL,
g726_close,
g726_decode_frame,
};