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
29typedef struct CNGContext {
30    LPCContext lpc;
31    int order;
32    int32_t *samples32;
33    double *ref_coef;
34} CNGContext;
35
36static av_cold int cng_encode_close(AVCodecContext *avctx)
37{
38    CNGContext *p = avctx->priv_data;
39    ff_lpc_end(&p->lpc);
40    av_free(p->samples32);
41    av_free(p->ref_coef);
42    return 0;
43}
44
45static 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        cng_encode_close(avctx);
63        return AVERROR(ENOMEM);
64    }
65
66    return 0;
67}
68
69static int cng_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
70                            const AVFrame *frame, int *got_packet_ptr)
71{
72    CNGContext *p = avctx->priv_data;
73    int ret, i;
74    double energy = 0;
75    int qdbov;
76    int16_t *samples = (int16_t*) frame->data[0];
77
78    if ((ret = ff_alloc_packet(avpkt, 1 + p->order))) {
79        av_log(avctx, AV_LOG_ERROR, "Error getting output packet\n");
80        return ret;
81    }
82
83    for (i = 0; i < frame->nb_samples; i++) {
84        p->samples32[i] = samples[i];
85        energy += samples[i] * samples[i];
86    }
87    energy /= frame->nb_samples;
88    if (energy > 0) {
89        double dbov = 10 * log10(energy / 1081109975);
90        qdbov = av_clip(-floor(dbov), 0, 127);
91    } else {
92        qdbov = 127;
93    }
94    ret = ff_lpc_calc_ref_coefs(&p->lpc, p->samples32, p->order, p->ref_coef);
95    avpkt->data[0] = qdbov;
96    for (i = 0; i < p->order; i++)
97        avpkt->data[1 + i] = p->ref_coef[i] * 127 + 127;
98
99    *got_packet_ptr = 1;
100    avpkt->size = 1 + p->order;
101
102    return 0;
103}
104
105AVCodec ff_comfortnoise_encoder = {
106    .name           = "comfortnoise",
107    .long_name      = NULL_IF_CONFIG_SMALL("RFC 3389 comfort noise generator"),
108    .type           = AVMEDIA_TYPE_AUDIO,
109    .id             = AV_CODEC_ID_COMFORT_NOISE,
110    .priv_data_size = sizeof(CNGContext),
111    .init           = cng_encode_init,
112    .encode2        = cng_encode_frame,
113    .close          = cng_encode_close,
114    .sample_fmts    = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
115                                                     AV_SAMPLE_FMT_NONE },
116};
117