2 * RFC 3389 comfort noise generator
3 * Copyright (c) 2012 Martin Storsjo
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 #include "libavutil/common.h"
26 #include "celp_filters.h"
27 #include "libavutil/lfg.h"
29 typedef struct CNGContext {
31 float *refl_coef, *target_refl_coef;
34 int energy, target_energy;
41 static av_cold int cng_decode_close(AVCodecContext *avctx)
43 CNGContext *p = avctx->priv_data;
44 av_free(p->refl_coef);
45 av_free(p->target_refl_coef);
47 av_free(p->filter_out);
48 av_free(p->excitation);
52 static av_cold int cng_decode_init(AVCodecContext *avctx)
54 CNGContext *p = avctx->priv_data;
56 avctx->sample_fmt = AV_SAMPLE_FMT_S16;
58 avctx->sample_rate = 8000;
60 avcodec_get_frame_defaults(&p->avframe);
61 avctx->coded_frame = &p->avframe;
63 avctx->frame_size = 640;
64 p->refl_coef = av_mallocz(p->order * sizeof(*p->refl_coef));
65 p->target_refl_coef = av_mallocz(p->order * sizeof(*p->target_refl_coef));
66 p->lpc_coef = av_mallocz(p->order * sizeof(*p->lpc_coef));
67 p->filter_out = av_mallocz((avctx->frame_size + p->order) *
68 sizeof(*p->filter_out));
69 p->excitation = av_mallocz(avctx->frame_size * sizeof(*p->excitation));
70 if (!p->refl_coef || !p->target_refl_coef || !p->lpc_coef ||
71 !p->filter_out || !p->excitation) {
72 cng_decode_close(avctx);
73 return AVERROR(ENOMEM);
76 av_lfg_init(&p->lfg, 0);
81 static void make_lpc_coefs(float *lpc, const float *refl, int order)
88 for (m = 0; m < order; m++) {
90 for (i = 0; i < m; i++)
91 next[i] = cur[i] + refl[m] * cur[m - i - 1];
92 FFSWAP(float*, next, cur);
95 memcpy(lpc, cur, sizeof(*lpc) * order);
98 static void cng_decode_flush(AVCodecContext *avctx)
100 CNGContext *p = avctx->priv_data;
104 static int cng_decode_frame(AVCodecContext *avctx, void *data,
105 int *got_frame_ptr, AVPacket *avpkt)
108 CNGContext *p = avctx->priv_data;
109 int buf_size = avpkt->size;
116 int dbov = -avpkt->data[0];
117 p->target_energy = 1081109975 * pow(10, dbov / 10.0) * 0.75;
118 memset(p->target_refl_coef, 0, p->order * sizeof(*p->target_refl_coef));
119 for (i = 0; i < FFMIN(avpkt->size - 1, p->order); i++) {
120 p->target_refl_coef[i] = (avpkt->data[1 + i] - 127) / 128.0;
125 p->energy = p->energy / 2 + p->target_energy / 2;
126 for (i = 0; i < p->order; i++)
127 p->refl_coef[i] = 0.6 *p->refl_coef[i] + 0.4 * p->target_refl_coef[i];
129 p->energy = p->target_energy;
130 memcpy(p->refl_coef, p->target_refl_coef, p->order * sizeof(*p->refl_coef));
133 make_lpc_coefs(p->lpc_coef, p->refl_coef, p->order);
135 for (i = 0; i < p->order; i++)
136 e *= 1.0 - p->refl_coef[i]*p->refl_coef[i];
138 scaling = sqrt(e * p->energy / 1081109975);
139 for (i = 0; i < avctx->frame_size; i++) {
140 int r = (av_lfg_get(&p->lfg) & 0xffff) - 0x8000;
141 p->excitation[i] = scaling * r;
143 ff_celp_lp_synthesis_filterf(p->filter_out + p->order, p->lpc_coef,
144 p->excitation, avctx->frame_size, p->order);
146 p->avframe.nb_samples = avctx->frame_size;
147 if ((ret = avctx->get_buffer(avctx, &p->avframe)) < 0) {
148 av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
151 buf_out = (int16_t *)p->avframe.data[0];
152 for (i = 0; i < avctx->frame_size; i++)
153 buf_out[i] = p->filter_out[i + p->order];
154 memcpy(p->filter_out, p->filter_out + avctx->frame_size,
155 p->order * sizeof(*p->filter_out));
158 *(AVFrame *)data = p->avframe;
163 AVCodec ff_comfortnoise_decoder = {
164 .name = "comfortnoise",
165 .type = AVMEDIA_TYPE_AUDIO,
166 .id = AV_CODEC_ID_COMFORT_NOISE,
167 .priv_data_size = sizeof(CNGContext),
168 .init = cng_decode_init,
169 .decode = cng_decode_frame,
170 .flush = cng_decode_flush,
171 .close = cng_decode_close,
172 .long_name = NULL_IF_CONFIG_SMALL("RFC 3389 comfort noise generator"),
173 .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
174 AV_SAMPLE_FMT_NONE },
175 .capabilities = CODEC_CAP_DELAY | CODEC_CAP_DR1,