1 /*
2 * RFC 3389 comfort noise generator
3 * Copyright (c) 2012 Martin Storsjo
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
20 */
21
22 #include <math.h>
23
24 #include "libavutil/common.h"
25 #include "avcodec.h"
26 #include "internal.h"
27 #include "lpc.h"
28
29 typedef struct CNGContext {
30 LPCContext lpc;
31 int order;
32 int32_t *samples32;
33 double *ref_coef;
34 } CNGContext;
35
cng_encode_close(AVCodecContext * avctx)36 static av_cold int cng_encode_close(AVCodecContext *avctx)
37 {
38 CNGContext *p = avctx->priv_data;
39 ff_lpc_end(&p->lpc);
40 av_freep(&p->samples32);
41 av_freep(&p->ref_coef);
42 return 0;
43 }
44
cng_encode_init(AVCodecContext * avctx)45 static av_cold int cng_encode_init(AVCodecContext *avctx)
46 {
47 CNGContext *p = avctx->priv_data;
48 int ret;
49
50 if (avctx->channels != 1) {
51 av_log(avctx, AV_LOG_ERROR, "Only mono supported\n");
52 return AVERROR(EINVAL);
53 }
54
55 avctx->frame_size = 640;
56 p->order = 10;
57 if ((ret = ff_lpc_init(&p->lpc, avctx->frame_size, p->order, FF_LPC_TYPE_LEVINSON)) < 0)
58 return ret;
59 p->samples32 = av_malloc_array(avctx->frame_size, sizeof(*p->samples32));
60 p->ref_coef = av_malloc_array(p->order, sizeof(*p->ref_coef));
61 if (!p->samples32 || !p->ref_coef)
62 return AVERROR(ENOMEM);
63
64 return 0;
65 }
66
cng_encode_frame(AVCodecContext * avctx,AVPacket * avpkt,const AVFrame * frame,int * got_packet_ptr)67 static int cng_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
68 const AVFrame *frame, int *got_packet_ptr)
69 {
70 CNGContext *p = avctx->priv_data;
71 int ret, i;
72 double energy = 0;
73 int qdbov;
74 int16_t *samples = (int16_t*) frame->data[0];
75
76 if ((ret = ff_alloc_packet2(avctx, avpkt, 1 + p->order, 1 + p->order))) {
77 av_log(avctx, AV_LOG_ERROR, "Error getting output packet\n");
78 return ret;
79 }
80
81 for (i = 0; i < frame->nb_samples; i++) {
82 p->samples32[i] = samples[i];
83 energy += samples[i] * samples[i];
84 }
85 energy /= frame->nb_samples;
86 if (energy > 0) {
87 double dbov = 10 * log10(energy / 1081109975);
88 qdbov = av_clip_uintp2(-floor(dbov), 7);
89 } else {
90 qdbov = 127;
91 }
92 ff_lpc_calc_ref_coefs(&p->lpc, p->samples32, p->order, p->ref_coef);
93 avpkt->data[0] = qdbov;
94 for (i = 0; i < p->order; i++)
95 avpkt->data[1 + i] = p->ref_coef[i] * 127 + 127;
96
97 *got_packet_ptr = 1;
98 av_assert1(avpkt->size == 1 + p->order);
99
100 return 0;
101 }
102
103 AVCodec ff_comfortnoise_encoder = {
104 .name = "comfortnoise",
105 .long_name = NULL_IF_CONFIG_SMALL("RFC 3389 comfort noise generator"),
106 .type = AVMEDIA_TYPE_AUDIO,
107 .id = AV_CODEC_ID_COMFORT_NOISE,
108 .priv_data_size = sizeof(CNGContext),
109 .init = cng_encode_init,
110 .encode2 = cng_encode_frame,
111 .close = cng_encode_close,
112 .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
113 AV_SAMPLE_FMT_NONE },
114 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
115 };
116