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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_free(p->refl_coef);
  45.     av_free(p->target_refl_coef);
  46.     av_free(p->lpc_coef);
  47.     av_free(p->filter_out);
  48.     av_free(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(p->order * sizeof(*p->refl_coef));
  63.     p->target_refl_coef = av_mallocz(p->order * sizeof(*p->target_refl_coef));
  64.     p->lpc_coef         = av_mallocz(p->order * sizeof(*p->lpc_coef));
  65.     p->filter_out       = av_mallocz((avctx->frame_size + p->order) *
  66.                                      sizeof(*p->filter_out));
  67.     p->excitation       = av_mallocz(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. };
  172.