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/*
* RFC 3389 comfort noise generator
* Copyright (c) 2012 Martin Storsjo
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <math.h>
#include "libavutil/common.h"
#include "avcodec.h"
#include "celp_filters.h"
#include "libavutil/lfg.h"
typedef struct CNGContext {
AVFrame avframe;
float *refl_coef, *target_refl_coef;
float *lpc_coef;
int order;
int energy, target_energy;
float *filter_out;
float *excitation;
AVLFG lfg;
} CNGContext;
static av_cold int cng_decode_close(AVCodecContext *avctx)
{
CNGContext *p = avctx->priv_data;
av_free(p->refl_coef);
av_free(p->target_refl_coef);
av_free(p->lpc_coef);
av_free(p->filter_out);
av_free(p->excitation);
return 0;
}
static av_cold int cng_decode_init(AVCodecContext *avctx)
{
CNGContext *p = avctx->priv_data;
avctx->sample_fmt = AV_SAMPLE_FMT_S16;
avctx->channels = 1;
avctx->sample_rate = 8000;
avcodec_get_frame_defaults(&p->avframe);
avctx->coded_frame = &p->avframe;
p->order = 12;
avctx->frame_size = 640;
p->refl_coef = av_mallocz(p->order * sizeof(*p->refl_coef));
p->target_refl_coef = av_mallocz(p->order * sizeof(*p->target_refl_coef));
p->lpc_coef = av_mallocz(p->order * sizeof(*p->lpc_coef));
p->filter_out = av_mallocz((avctx->frame_size + p->order) *
sizeof(*p->filter_out));
p->excitation = av_mallocz(avctx->frame_size * sizeof(*p->excitation));
if (!p->refl_coef || !p->target_refl_coef || !p->lpc_coef ||
!p->filter_out || !p->excitation) {
cng_decode_close(avctx);
return AVERROR(ENOMEM);
}
av_lfg_init(&p->lfg, 0);
return 0;
}
static void make_lpc_coefs(float *lpc, const float *refl, int order)
{
float buf[100];
float *next, *cur;
int m, i;
next = buf;
cur = lpc;
for (m = 0; m < order; m++) {
next[m] = refl[m];
for (i = 0; i < m; i++)
next[i] = cur[i] + refl[m] * cur[m - i - 1];
FFSWAP(float*, next, cur);
}
if (cur != lpc)
memcpy(lpc, cur, sizeof(*lpc) * order);
}
static int cng_decode_frame(AVCodecContext *avctx, void *data,
int *got_frame_ptr, AVPacket *avpkt)
{
CNGContext *p = avctx->priv_data;
int buf_size = avpkt->size;
int ret, i;
int16_t *buf_out;
float e = 1.0;
float scaling;
if (avpkt->size) {
float dbov = -avpkt->data[0] / 10.0;
p->target_energy = 1081109975 * pow(10, dbov) * 0.75;
memset(p->target_refl_coef, 0, p->order * sizeof(*p->target_refl_coef));
for (i = 0; i < FFMIN(avpkt->size - 1, p->order); i++) {
p->target_refl_coef[i] = (avpkt->data[1 + i] - 127) / 128.0;
}
}
p->energy = p->energy / 2 + p->target_energy / 2;
for (i = 0; i < p->order; i++)
p->refl_coef[i] = 0.6 *p->refl_coef[i] + 0.4 * p->target_refl_coef[i];
make_lpc_coefs(p->lpc_coef, p->refl_coef, p->order);
for (i = 0; i < p->order; i++)
e *= 1.0 - p->refl_coef[i]*p->refl_coef[i];
scaling = sqrt(e * p->energy / 1081109975);
for (i = 0; i < avctx->frame_size; i++) {
int r = (av_lfg_get(&p->lfg) & 0xffff) - 0x8000;
p->excitation[i] = scaling * r;
}
ff_celp_lp_synthesis_filterf(p->filter_out + p->order, p->lpc_coef,
p->excitation, avctx->frame_size, p->order);
p->avframe.nb_samples = avctx->frame_size;
if ((ret = avctx->get_buffer(avctx, &p->avframe)) < 0) {
av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
return ret;
}
buf_out = (int16_t *)p->avframe.data[0];
for (i = 0; i < avctx->frame_size; i++)
buf_out[i] = p->filter_out[i + p->order];
memcpy(p->filter_out, p->filter_out + avctx->frame_size,
p->order * sizeof(*p->filter_out));
*got_frame_ptr = 1;
*(AVFrame *)data = p->avframe;
return buf_size;
}
AVCodec ff_comfortnoise_decoder = {
.name = "comfortnoise",
.type = AVMEDIA_TYPE_AUDIO,
.id = AV_CODEC_ID_COMFORT_NOISE,
.priv_data_size = sizeof(CNGContext),
.init = cng_decode_init,
.decode = cng_decode_frame,
.close = cng_decode_close,
.long_name = NULL_IF_CONFIG_SMALL("RFC 3389 comfort noise generator"),
.sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
AV_SAMPLE_FMT_NONE },
.capabilities = CODEC_CAP_DELAY | CODEC_CAP_DR1,
};
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