libavcodec/cngenc.c

   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/avassert.h"
  25 #include "libavutil/common.h"
  26 #include "libavutil/mem.h"
  27 #include "avcodec.h"
  28 #include "codec_internal.h"
  29 #include "encode.h"
  30 #include "lpc.h"
  31
  32 typedef struct CNGContext {
  33     LPCContext lpc;
  34     int order;
  35     int32_t *samples32;
  36     double *ref_coef;
  37 } CNGContext;
  38
  39 static av_cold int cng_encode_close(AVCodecContext *avctx)
  40 {
  41     CNGContext *p = avctx->priv_data;
  42     ff_lpc_end(&p->lpc);
  43     av_freep(&p->samples32);
  44     av_freep(&p->ref_coef);
  45     return 0;
  46 }
  47
  48 static av_cold int cng_encode_init(AVCodecContext *avctx)
  49 {
  50     CNGContext *p = avctx->priv_data;
  51     int ret;
  52
  53     avctx->frame_size = 640;
  54     p->order = 10;
  55     if ((ret = ff_lpc_init(&p->lpc, avctx->frame_size, p->order, FF_LPC_TYPE_LEVINSON)) < 0)
  56         return ret;
  57     p->samples32 = av_malloc_array(avctx->frame_size, sizeof(*p->samples32));
  58     p->ref_coef = av_malloc_array(p->order, sizeof(*p->ref_coef));
  59     if (!p->samples32 || !p->ref_coef)
  60         return AVERROR(ENOMEM);
  61
  62     return 0;
  63 }
  64
  65 static int cng_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
  66                             const AVFrame *frame, int *got_packet_ptr)
  67 {
  68     CNGContext *p = avctx->priv_data;
  69     int ret, i;
  70     double energy = 0;
  71     int qdbov;
  72     const int16_t *samples = (const int16_t*) frame->data[0];
  73
  74     if ((ret = ff_get_encode_buffer(avctx, avpkt, 1 + p->order, 0))) {
  75         av_log(avctx, AV_LOG_ERROR, "Error getting output packet\n");
  76         return ret;
  77     }
  78
  79     for (i = 0; i < frame->nb_samples; i++) {
  80         p->samples32[i] = samples[i];
  81         energy += samples[i] * samples[i];
  82     }
  83     energy /= frame->nb_samples;
  84     if (energy > 0) {
  85         double dbov = 10 * log10(energy / 1081109975);
  86         qdbov = av_clip_uintp2(-floor(dbov), 7);
  87     } else {
  88         qdbov = 127;
  89     }
  90     ff_lpc_calc_ref_coefs(&p->lpc, p->samples32, p->order, p->ref_coef);
  91     avpkt->data[0] = qdbov;
  92     for (i = 0; i < p->order; i++)
  93         avpkt->data[1 + i] = p->ref_coef[i] * 127 + 127;
  94
  95     *got_packet_ptr = 1;
  96     av_assert1(avpkt->size == 1 + p->order);
  97
  98     return 0;
  99 }
 100
 101 const FFCodec ff_comfortnoise_encoder = {
 102     .p.name         = "comfortnoise",
 103     CODEC_LONG_NAME("RFC 3389 comfort noise generator"),
 104     .p.type         = AVMEDIA_TYPE_AUDIO,
 105     .p.id           = AV_CODEC_ID_COMFORT_NOISE,
 106     .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,
 107     .priv_data_size = sizeof(CNGContext),
 108     .init           = cng_encode_init,
 109     FF_CODEC_ENCODE_CB(cng_encode_frame),
 110     .close          = cng_encode_close,
 111     .p.sample_fmts  = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
 112                                                      AV_SAMPLE_FMT_NONE },
 113     .p.ch_layouts   = (const AVChannelLayout[]){ AV_CHANNEL_LAYOUT_MONO, { 0 } },
 114     .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
 115 };