2 * RFC 3389 comfort noise generator
3 * Copyright (c) 2012 Martin Storsjo
5 * This file is part of Libav.
7 * Libav 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 * Libav 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 Libav; 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;
40 static av_cold int cng_decode_close(AVCodecContext *avctx)
42 CNGContext *p = avctx->priv_data;
43 av_free(p->refl_coef);
44 av_free(p->target_refl_coef);
46 av_free(p->filter_out);
47 av_free(p->excitation);
51 static av_cold int cng_decode_init(AVCodecContext *avctx)
53 CNGContext *p = avctx->priv_data;
55 avctx->sample_fmt = AV_SAMPLE_FMT_S16;
57 avctx->sample_rate = 8000;
59 avcodec_get_frame_defaults(&p->avframe);
60 avctx->coded_frame = &p->avframe;
62 avctx->frame_size = 640;
63 p->refl_coef = av_mallocz(p->order * sizeof(*p->refl_coef));
64 p->target_refl_coef = av_mallocz(p->order * sizeof(*p->target_refl_coef));
65 p->lpc_coef = av_mallocz(p->order * sizeof(*p->lpc_coef));
66 p->filter_out = av_mallocz((avctx->frame_size + p->order) *
67 sizeof(*p->filter_out));
68 p->excitation = av_mallocz(avctx->frame_size * sizeof(*p->excitation));
69 if (!p->refl_coef || !p->target_refl_coef || !p->lpc_coef ||
70 !p->filter_out || !p->excitation) {
71 cng_decode_close(avctx);
72 return AVERROR(ENOMEM);
75 av_lfg_init(&p->lfg, 0);
80 static void make_lpc_coefs(float *lpc, const float *refl, int order)
87 for (m = 0; m < order; m++) {
89 for (i = 0; i < m; i++)
90 next[i] = cur[i] + refl[m] * cur[m - i - 1];
91 FFSWAP(float*, next, cur);
94 memcpy(lpc, cur, sizeof(*lpc) * order);
97 static int cng_decode_frame(AVCodecContext *avctx, void *data,
98 int *got_frame_ptr, AVPacket *avpkt)
101 CNGContext *p = avctx->priv_data;
102 int buf_size = avpkt->size;
109 int dbov = -avpkt->data[0];
110 p->target_energy = 1081109975 * pow(10, dbov / 10.0) * 0.75;
111 memset(p->target_refl_coef, 0, p->order * sizeof(*p->target_refl_coef));
112 for (i = 0; i < FFMIN(avpkt->size - 1, p->order); i++) {
113 p->target_refl_coef[i] = (avpkt->data[1 + i] - 127) / 128.0;
117 p->energy = p->energy / 2 + p->target_energy / 2;
118 for (i = 0; i < p->order; i++)
119 p->refl_coef[i] = 0.6 *p->refl_coef[i] + 0.4 * p->target_refl_coef[i];
120 make_lpc_coefs(p->lpc_coef, p->refl_coef, p->order);
122 for (i = 0; i < p->order; i++)
123 e *= 1.0 - p->refl_coef[i]*p->refl_coef[i];
125 scaling = sqrt(e * p->energy / 1081109975);
126 for (i = 0; i < avctx->frame_size; i++) {
127 int r = (av_lfg_get(&p->lfg) & 0xffff) - 0x8000;
128 p->excitation[i] = scaling * r;
130 ff_celp_lp_synthesis_filterf(p->filter_out + p->order, p->lpc_coef,
131 p->excitation, avctx->frame_size, p->order);
133 p->avframe.nb_samples = avctx->frame_size;
134 if ((ret = avctx->get_buffer(avctx, &p->avframe)) < 0) {
135 av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
138 buf_out = (int16_t *)p->avframe.data[0];
139 for (i = 0; i < avctx->frame_size; i++)
140 buf_out[i] = p->filter_out[i + p->order];
141 memcpy(p->filter_out, p->filter_out + avctx->frame_size,
142 p->order * sizeof(*p->filter_out));
145 *(AVFrame *)data = p->avframe;
150 AVCodec ff_comfortnoise_decoder = {
151 .name = "comfortnoise",
152 .type = AVMEDIA_TYPE_AUDIO,
153 .id = AV_CODEC_ID_COMFORT_NOISE,
154 .priv_data_size = sizeof(CNGContext),
155 .init = cng_decode_init,
156 .decode = cng_decode_frame,
157 .close = cng_decode_close,
158 .long_name = NULL_IF_CONFIG_SMALL("RFC 3389 comfort noise generator"),
159 .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
160 AV_SAMPLE_FMT_NONE },
161 .capabilities = CODEC_CAP_DELAY | CODEC_CAP_DR1,