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FFmpeg/libavcodec/gsmdec.c
Reimar Döffinger 6f2c05f307 Document how the ref_buf is used. 
Originally committed as revision 24551 to svn://svn.ffmpeg.org/ffmpeg/trunk
2010-07-27 17:11:13 +00:00

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/*
* gsm 06.10 decoder
* Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
*
* 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
*/
/**
* @file
* GSM decoder
*/
#define ALT_BITSTREAM_READER_LE
#include "avcodec.h"
#include "get_bits.h"
// input and output sizes in byte
#define GSM_BLOCK_SIZE 33
#define GSM_MS_BLOCK_SIZE 65
#define GSM_FRAME_SIZE 160
typedef struct {
// Contains first 120 elements from the previous frame
// (used by long_term_synth according to the "lag"),
// then in the following 160 elements the current
// frame is constructed.
int16_t ref_buf[280];
int v[9];
int lar[2][8];
int lar_idx;
int msr;
} GSMContext;
static av_cold int gsm_init(AVCodecContext *avctx)
{
avctx->channels = 1;
if (!avctx->sample_rate)
avctx->sample_rate = 8000;
avctx->sample_fmt = SAMPLE_FMT_S16;
switch (avctx->codec_id) {
case CODEC_ID_GSM:
avctx->frame_size = GSM_FRAME_SIZE;
avctx->block_align = GSM_BLOCK_SIZE;
break;
case CODEC_ID_GSM_MS:
avctx->frame_size = 2 * GSM_FRAME_SIZE;
avctx->block_align = GSM_MS_BLOCK_SIZE;
}
return 0;
}
static const int16_t dequant_tab[64][8] = {
{ -28, -20, -12, -4, 4, 12, 20, 28},
{ -56, -40, -24, -8, 8, 24, 40, 56},
{ -84, -60, -36, -12, 12, 36, 60, 84},
{ -112, -80, -48, -16, 16, 48, 80, 112},
{ -140, -100, -60, -20, 20, 60, 100, 140},
{ -168, -120, -72, -24, 24, 72, 120, 168},
{ -196, -140, -84, -28, 28, 84, 140, 196},
{ -224, -160, -96, -32, 32, 96, 160, 224},
{ -252, -180, -108, -36, 36, 108, 180, 252},
{ -280, -200, -120, -40, 40, 120, 200, 280},
{ -308, -220, -132, -44, 44, 132, 220, 308},
{ -336, -240, -144, -48, 48, 144, 240, 336},
{ -364, -260, -156, -52, 52, 156, 260, 364},
{ -392, -280, -168, -56, 56, 168, 280, 392},
{ -420, -300, -180, -60, 60, 180, 300, 420},
{ -448, -320, -192, -64, 64, 192, 320, 448},
{ -504, -360, -216, -72, 72, 216, 360, 504},
{ -560, -400, -240, -80, 80, 240, 400, 560},
{ -616, -440, -264, -88, 88, 264, 440, 616},
{ -672, -480, -288, -96, 96, 288, 480, 672},
{ -728, -520, -312, -104, 104, 312, 520, 728},
{ -784, -560, -336, -112, 112, 336, 560, 784},
{ -840, -600, -360, -120, 120, 360, 600, 840},
{ -896, -640, -384, -128, 128, 384, 640, 896},
{ -1008, -720, -432, -144, 144, 432, 720, 1008},
{ -1120, -800, -480, -160, 160, 480, 800, 1120},
{ -1232, -880, -528, -176, 176, 528, 880, 1232},
{ -1344, -960, -576, -192, 192, 576, 960, 1344},
{ -1456, -1040, -624, -208, 208, 624, 1040, 1456},
{ -1568, -1120, -672, -224, 224, 672, 1120, 1568},
{ -1680, -1200, -720, -240, 240, 720, 1200, 1680},
{ -1792, -1280, -768, -256, 256, 768, 1280, 1792},
{ -2016, -1440, -864, -288, 288, 864, 1440, 2016},
{ -2240, -1600, -960, -320, 320, 960, 1600, 2240},
{ -2464, -1760, -1056, -352, 352, 1056, 1760, 2464},
{ -2688, -1920, -1152, -384, 384, 1152, 1920, 2688},
{ -2912, -2080, -1248, -416, 416, 1248, 2080, 2912},
{ -3136, -2240, -1344, -448, 448, 1344, 2240, 3136},
{ -3360, -2400, -1440, -480, 480, 1440, 2400, 3360},
{ -3584, -2560, -1536, -512, 512, 1536, 2560, 3584},
{ -4032, -2880, -1728, -576, 576, 1728, 2880, 4032},
{ -4480, -3200, -1920, -640, 640, 1920, 3200, 4480},
{ -4928, -3520, -2112, -704, 704, 2112, 3520, 4928},
{ -5376, -3840, -2304, -768, 768, 2304, 3840, 5376},
{ -5824, -4160, -2496, -832, 832, 2496, 4160, 5824},
{ -6272, -4480, -2688, -896, 896, 2688, 4480, 6272},
{ -6720, -4800, -2880, -960, 960, 2880, 4800, 6720},
{ -7168, -5120, -3072, -1024, 1024, 3072, 5120, 7168},
{ -8063, -5759, -3456, -1152, 1152, 3456, 5760, 8064},
{ -8959, -6399, -3840, -1280, 1280, 3840, 6400, 8960},
{ -9855, -7039, -4224, -1408, 1408, 4224, 7040, 9856},
{-10751, -7679, -4608, -1536, 1536, 4608, 7680, 10752},
{-11647, -8319, -4992, -1664, 1664, 4992, 8320, 11648},
{-12543, -8959, -5376, -1792, 1792, 5376, 8960, 12544},
{-13439, -9599, -5760, -1920, 1920, 5760, 9600, 13440},
{-14335, -10239, -6144, -2048, 2048, 6144, 10240, 14336},
{-16127, -11519, -6912, -2304, 2304, 6912, 11519, 16127},
{-17919, -12799, -7680, -2560, 2560, 7680, 12799, 17919},
{-19711, -14079, -8448, -2816, 2816, 8448, 14079, 19711},
{-21503, -15359, -9216, -3072, 3072, 9216, 15359, 21503},
{-23295, -16639, -9984, -3328, 3328, 9984, 16639, 23295},
{-25087, -17919, -10752, -3584, 3584, 10752, 17919, 25087},
{-26879, -19199, -11520, -3840, 3840, 11520, 19199, 26879},
{-28671, -20479, -12288, -4096, 4096, 12288, 20479, 28671}
};
static void apcm_dequant_add(GetBitContext *gb, int16_t *dst)
{
int i;
int maxidx = get_bits(gb, 6);
const int16_t *tab = dequant_tab[maxidx];
for (i = 0; i < 13; i++)
dst[3*i] += tab[get_bits(gb, 3)];
}
static inline int gsm_mult(int a, int b)
{
return (a * b + (1 << 14)) >> 15;
}
static const uint16_t long_term_gain_tab[4] = {
3277, 11469, 21299, 32767
};
static void long_term_synth(int16_t *dst, int lag, int gain_idx)
{
int i;
const int16_t *src = dst - lag;
uint16_t gain = long_term_gain_tab[gain_idx];
for (i = 0; i < 40; i++)
dst[i] = gsm_mult(gain, src[i]);
}
static inline int decode_log_area(int coded, int factor, int offset)
{
coded <<= 10;
coded -= offset;
return gsm_mult(coded, factor) << 1;
}
static av_noinline int get_rrp(int filtered)
{
int abs = FFABS(filtered);
if (abs < 11059) abs <<= 1;
else if (abs < 20070) abs += 11059;
else abs = (abs >> 2) + 26112;
return filtered < 0 ? -abs : abs;
}
static int filter_value(int in, int rrp[8], int v[9])
{
int i;
for (i = 7; i >= 0; i--) {
in -= gsm_mult(rrp[i], v[i]);
v[i + 1] = v[i] + gsm_mult(rrp[i], in);
}
v[0] = in;
return in;
}
static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)
{
int i;
int rrp[8];
int *lar = ctx->lar[ctx->lar_idx];
int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];
for (i = 0; i < 8; i++)
rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));
for (i = 0; i < 13; i++)
dst[i] = filter_value(src[i], rrp, ctx->v);
for (i = 0; i < 8; i++)
rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar [i] >> 1));
for (i = 13; i < 27; i++)
dst[i] = filter_value(src[i], rrp, ctx->v);
for (i = 0; i < 8; i++)
rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar [i] >> 1) + (lar[i] >> 2));
for (i = 27; i < 40; i++)
dst[i] = filter_value(src[i], rrp, ctx->v);
for (i = 0; i < 8; i++)
rrp[i] = get_rrp(lar[i]);
for (i = 40; i < 160; i++)
dst[i] = filter_value(src[i], rrp, ctx->v);
ctx->lar_idx ^= 1;
}
static int postprocess(int16_t *data, int msr)
{
int i;
for (i = 0; i < 160; i++) {
msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));
data[i] = av_clip_int16(msr << 1) & ~7;
}
return msr;
}
static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,
GetBitContext *gb)
{
GSMContext *ctx = avctx->priv_data;
int i;
int16_t *ref_dst = ctx->ref_buf + 120;
int *lar = ctx->lar[ctx->lar_idx];
lar[0] = decode_log_area(get_bits(gb, 6), 13107, 1 << 15);
lar[1] = decode_log_area(get_bits(gb, 6), 13107, 1 << 15);
lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);
lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);
lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) + 94*2);
lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);
lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) - 341*2);
lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);
for (i = 0; i < 4; i++) {
int lag = get_bits(gb, 7);
int gain_idx = get_bits(gb, 2);
int offset = get_bits(gb, 2);
lag = av_clip(lag, 40, 120);
long_term_synth(ref_dst, lag, gain_idx);
apcm_dequant_add(gb, ref_dst + offset);
ref_dst += 40;
}
memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));
short_term_synth(ctx, samples, ctx->ref_buf + 120);
// for optimal speed this could be merged with short_term_synth,
// not done yet because it is a bit ugly
ctx->msr = postprocess(samples, ctx->msr);
return 0;
}
static int gsm_decode_frame(AVCodecContext *avctx, void *data,
int *data_size, AVPacket *avpkt)
{
int res;
GetBitContext gb;
const uint8_t *buf = avpkt->data;
int buf_size = avpkt->size;
int16_t *samples = data;
int frame_bytes = 2 * avctx->frame_size;
if (*data_size < frame_bytes)
return -1;
*data_size = 0;
if(buf_size < avctx->block_align)
return AVERROR_INVALIDDATA;
init_get_bits(&gb, buf, buf_size * 8);
switch (avctx->codec_id) {
case CODEC_ID_GSM:
if (get_bits(&gb, 4) != 0xd)
av_log(avctx, AV_LOG_WARNING, "Missing GSM magic!\n");
res = gsm_decode_block(avctx, samples, &gb);
if (res < 0)
return res;
break;
case CODEC_ID_GSM_MS:
res = gsm_decode_block(avctx, samples, &gb);
if (res < 0)
return res;
res = gsm_decode_block(avctx, samples + GSM_FRAME_SIZE, &gb);
if (res < 0)
return res;
}
*data_size = frame_bytes;
return avctx->block_align;
}
AVCodec gsm_decoder = {
"gsm",
AVMEDIA_TYPE_AUDIO,
CODEC_ID_GSM,
sizeof(GSMContext),
gsm_init,
NULL,
NULL,
gsm_decode_frame,
.long_name = NULL_IF_CONFIG_SMALL("GSM"),
};
AVCodec gsm_ms_decoder = {
"gsm_ms",
AVMEDIA_TYPE_AUDIO,
CODEC_ID_GSM_MS,
sizeof(GSMContext),
gsm_init,
NULL,
NULL,
gsm_decode_frame,
.long_name = NULL_IF_CONFIG_SMALL("GSM Microsoft variant"),
};
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