FFmpeg: libavcodec/cngdec.c Source File

FFmpeg
cngdec.c
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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 "celp_filters.h"
27 #include "internal.h"
28 #include "libavutil/lfg.h"
29 
30  typedef struct CNGContext {
31   float *refl_coef, *target_refl_coef;
32   float *lpc_coef;
33   int order;
34   int energy, target_energy;
35   int inited;
36   float *filter_out;
37   float *excitation;
38   AVLFG lfg;
39 } CNGContext;
40 
41  static av_cold int cng_decode_close(AVCodecContext *avctx)
42 {
43  CNGContext *p = avctx->priv_data;
44  av_freep(&p->refl_coef);
45  av_freep(&p->target_refl_coef);
46  av_freep(&p->lpc_coef);
47  av_freep(&p->filter_out);
48  av_freep(&p->excitation);
49  return 0;
50 }
51 
52  static av_cold int cng_decode_init(AVCodecContext *avctx)
53 {
54  CNGContext *p = avctx->priv_data;
55 
56  avctx->sample_fmt = AV_SAMPLE_FMT_S16;
57  avctx->channels = 1;
58  avctx->sample_rate = 8000;
59 
60  p->order = 12;
61  avctx->frame_size = 640;
62  p->refl_coef = av_mallocz_array(p->order, sizeof(*p->refl_coef));
63  p->target_refl_coef = av_mallocz_array(p->order, sizeof(*p->target_refl_coef));
64  p->lpc_coef = av_mallocz_array(p->order, sizeof(*p->lpc_coef));
65  p->filter_out = av_mallocz_array(avctx->frame_size + p->order,
66  sizeof(*p->filter_out));
67  p->excitation = av_mallocz_array(avctx->frame_size, sizeof(*p->excitation));
68  if (!p->refl_coef || !p->target_refl_coef || !p->lpc_coef ||
69  !p->filter_out || !p->excitation) {
70  cng_decode_close(avctx);
71  return AVERROR(ENOMEM);
72  }
73 
74  av_lfg_init(&p->lfg, 0);
75 
76  return 0;
77 }
78 
79  static void make_lpc_coefs(float *lpc, const float *refl, int order)
80 {
81  float buf[100];
82  float *next, *cur;
83  int m, i;
84  next = buf;
85  cur = lpc;
86  for (m = 0; m < order; m++) {
87  next[m] = refl[m];
88  for (i = 0; i < m; i++)
89  next[i] = cur[i] + refl[m] * cur[m - i - 1];
90  FFSWAP(float*, next, cur);
91  }
92  if (cur != lpc)
93  memcpy(lpc, cur, sizeof(*lpc) * order);
94 }
95 
96  static void cng_decode_flush(AVCodecContext *avctx)
97 {
98  CNGContext *p = avctx->priv_data;
99  p->inited = 0;
100 }
101 
102  static int cng_decode_frame(AVCodecContext *avctx, void *data,
103  int *got_frame_ptr, AVPacket *avpkt)
104 {
105  AVFrame *frame = data;
106  CNGContext *p = avctx->priv_data;
107  int buf_size = avpkt->size;
108  int ret, i;
109  int16_t *buf_out;
110  float e = 1.0;
111  float scaling;
112 
113  if (avpkt->size) {
114  int dbov = -avpkt->data[0];
115  p->target_energy = 1081109975 * pow(10, dbov / 10.0) * 0.75;
116  memset(p->target_refl_coef, 0, p->order * sizeof(*p->target_refl_coef));
117  for (i = 0; i < FFMIN(avpkt->size - 1, p->order); i++) {
118  p->target_refl_coef[i] = (avpkt->data[1 + i] - 127) / 128.0;
119  }
120  }
121 
122  if (p->inited) {
123  p->energy = p->energy / 2 + p->target_energy / 2;
124  for (i = 0; i < p->order; i++)
125  p->refl_coef[i] = 0.6 *p->refl_coef[i] + 0.4 * p->target_refl_coef[i];
126  } else {
127  p->energy = p->target_energy;
128  memcpy(p->refl_coef, p->target_refl_coef, p->order * sizeof(*p->refl_coef));
129  p->inited = 1;
130  }
131  make_lpc_coefs(p->lpc_coef, p->refl_coef, p->order);
132 
133  for (i = 0; i < p->order; i++)
134  e *= 1.0 - p->refl_coef[i]*p->refl_coef[i];
135 
136  scaling = sqrt(e * p->energy / 1081109975);
137  for (i = 0; i < avctx->frame_size; i++) {
138  int r = (av_lfg_get(&p->lfg) & 0xffff) - 0x8000;
139  p->excitation[i] = scaling * r;
140  }
141  ff_celp_lp_synthesis_filterf(p->filter_out + p->order, p->lpc_coef,
142  p->excitation, avctx->frame_size, p->order);
143 
144  frame->nb_samples = avctx->frame_size;
145  if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
146  return ret;
147  buf_out = (int16_t *)frame->data[0];
148  for (i = 0; i < avctx->frame_size; i++)
149  buf_out[i] = p->filter_out[i + p->order];
150  memcpy(p->filter_out, p->filter_out + avctx->frame_size,
151  p->order * sizeof(*p->filter_out));
152 
153  *got_frame_ptr = 1;
154 
155  return buf_size;
156 }
157 
158  AVCodec ff_comfortnoise_decoder = {
159  .name = "comfortnoise",
160  .long_name = NULL_IF_CONFIG_SMALL("RFC 3389 comfort noise generator"),
161  .type = AVMEDIA_TYPE_AUDIO,
162  .id = AV_CODEC_ID_COMFORT_NOISE,
163  .priv_data_size = sizeof(CNGContext),
164  .init = cng_decode_init,
165  .decode = cng_decode_frame,
166  .flush = cng_decode_flush,
167  .close = cng_decode_close,
168  .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
169  AV_SAMPLE_FMT_NONE },
170  .capabilities = CODEC_CAP_DELAY | CODEC_CAP_DR1,
171 };
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