yading@10: /*
yading@10:  * RFC 3389 comfort noise generator
yading@10:  * Copyright (c) 2012 Martin Storsjo
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: #include <math.h>
yading@10: 
yading@10: #include "libavutil/common.h"
yading@10: #include "avcodec.h"
yading@10: #include "celp_filters.h"
yading@10: #include "internal.h"
yading@10: #include "libavutil/lfg.h"
yading@10: 
yading@10: typedef struct CNGContext {
yading@10:     float *refl_coef, *target_refl_coef;
yading@10:     float *lpc_coef;
yading@10:     int order;
yading@10:     int energy, target_energy;
yading@10:     int inited;
yading@10:     float *filter_out;
yading@10:     float *excitation;
yading@10:     AVLFG lfg;
yading@10: } CNGContext;
yading@10: 
yading@10: static av_cold int cng_decode_close(AVCodecContext *avctx)
yading@10: {
yading@10:     CNGContext *p = avctx->priv_data;
yading@10:     av_free(p->refl_coef);
yading@10:     av_free(p->target_refl_coef);
yading@10:     av_free(p->lpc_coef);
yading@10:     av_free(p->filter_out);
yading@10:     av_free(p->excitation);
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static av_cold int cng_decode_init(AVCodecContext *avctx)
yading@10: {
yading@10:     CNGContext *p = avctx->priv_data;
yading@10: 
yading@10:     avctx->sample_fmt  = AV_SAMPLE_FMT_S16;
yading@10:     avctx->channels    = 1;
yading@10:     avctx->sample_rate = 8000;
yading@10: 
yading@10:     p->order            = 12;
yading@10:     avctx->frame_size   = 640;
yading@10:     p->refl_coef        = av_mallocz(p->order * sizeof(*p->refl_coef));
yading@10:     p->target_refl_coef = av_mallocz(p->order * sizeof(*p->target_refl_coef));
yading@10:     p->lpc_coef         = av_mallocz(p->order * sizeof(*p->lpc_coef));
yading@10:     p->filter_out       = av_mallocz((avctx->frame_size + p->order) *
yading@10:                                      sizeof(*p->filter_out));
yading@10:     p->excitation       = av_mallocz(avctx->frame_size * sizeof(*p->excitation));
yading@10:     if (!p->refl_coef || !p->target_refl_coef || !p->lpc_coef ||
yading@10:         !p->filter_out || !p->excitation) {
yading@10:         cng_decode_close(avctx);
yading@10:         return AVERROR(ENOMEM);
yading@10:     }
yading@10: 
yading@10:     av_lfg_init(&p->lfg, 0);
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static void make_lpc_coefs(float *lpc, const float *refl, int order)
yading@10: {
yading@10:     float buf[100];
yading@10:     float *next, *cur;
yading@10:     int m, i;
yading@10:     next = buf;
yading@10:     cur  = lpc;
yading@10:     for (m = 0; m < order; m++) {
yading@10:         next[m] = refl[m];
yading@10:         for (i = 0; i < m; i++)
yading@10:             next[i] = cur[i] + refl[m] * cur[m - i - 1];
yading@10:         FFSWAP(float*, next, cur);
yading@10:     }
yading@10:     if (cur != lpc)
yading@10:         memcpy(lpc, cur, sizeof(*lpc) * order);
yading@10: }
yading@10: 
yading@10: static void cng_decode_flush(AVCodecContext *avctx)
yading@10: {
yading@10:     CNGContext *p = avctx->priv_data;
yading@10:     p->inited = 0;
yading@10: }
yading@10: 
yading@10: static int cng_decode_frame(AVCodecContext *avctx, void *data,
yading@10:                             int *got_frame_ptr, AVPacket *avpkt)
yading@10: {
yading@10:     AVFrame *frame = data;
yading@10:     CNGContext *p = avctx->priv_data;
yading@10:     int buf_size  = avpkt->size;
yading@10:     int ret, i;
yading@10:     int16_t *buf_out;
yading@10:     float e = 1.0;
yading@10:     float scaling;
yading@10: 
yading@10:     if (avpkt->size) {
yading@10:         int dbov = -avpkt->data[0];
yading@10:         p->target_energy = 1081109975 * pow(10, dbov / 10.0) * 0.75;
yading@10:         memset(p->target_refl_coef, 0, p->order * sizeof(*p->target_refl_coef));
yading@10:         for (i = 0; i < FFMIN(avpkt->size - 1, p->order); i++) {
yading@10:             p->target_refl_coef[i] = (avpkt->data[1 + i] - 127) / 128.0;
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     if (p->inited) {
yading@10:         p->energy = p->energy / 2 + p->target_energy / 2;
yading@10:         for (i = 0; i < p->order; i++)
yading@10:             p->refl_coef[i] = 0.6 *p->refl_coef[i] + 0.4 * p->target_refl_coef[i];
yading@10:     } else {
yading@10:         p->energy = p->target_energy;
yading@10:         memcpy(p->refl_coef, p->target_refl_coef, p->order * sizeof(*p->refl_coef));
yading@10:         p->inited = 1;
yading@10:     }
yading@10:     make_lpc_coefs(p->lpc_coef, p->refl_coef, p->order);
yading@10: 
yading@10:     for (i = 0; i < p->order; i++)
yading@10:         e *= 1.0 - p->refl_coef[i]*p->refl_coef[i];
yading@10: 
yading@10:     scaling = sqrt(e * p->energy / 1081109975);
yading@10:     for (i = 0; i < avctx->frame_size; i++) {
yading@10:         int r = (av_lfg_get(&p->lfg) & 0xffff) - 0x8000;
yading@10:         p->excitation[i] = scaling * r;
yading@10:     }
yading@10:     ff_celp_lp_synthesis_filterf(p->filter_out + p->order, p->lpc_coef,
yading@10:                                  p->excitation, avctx->frame_size, p->order);
yading@10: 
yading@10:     frame->nb_samples = avctx->frame_size;
yading@10:     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
yading@10:         return ret;
yading@10:     buf_out = (int16_t *)frame->data[0];
yading@10:     for (i = 0; i < avctx->frame_size; i++)
yading@10:         buf_out[i] = p->filter_out[i + p->order];
yading@10:     memcpy(p->filter_out, p->filter_out + avctx->frame_size,
yading@10:            p->order * sizeof(*p->filter_out));
yading@10: 
yading@10:     *got_frame_ptr = 1;
yading@10: 
yading@10:     return buf_size;
yading@10: }
yading@10: 
yading@10: AVCodec ff_comfortnoise_decoder = {
yading@10:     .name           = "comfortnoise",
yading@10:     .type           = AVMEDIA_TYPE_AUDIO,
yading@10:     .id             = AV_CODEC_ID_COMFORT_NOISE,
yading@10:     .priv_data_size = sizeof(CNGContext),
yading@10:     .init           = cng_decode_init,
yading@10:     .decode         = cng_decode_frame,
yading@10:     .flush          = cng_decode_flush,
yading@10:     .close          = cng_decode_close,
yading@10:     .long_name      = NULL_IF_CONFIG_SMALL("RFC 3389 comfort noise generator"),
yading@10:     .sample_fmts    = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
yading@10:                                                      AV_SAMPLE_FMT_NONE },
yading@10:     .capabilities   = CODEC_CAP_DELAY | CODEC_CAP_DR1,
yading@10: };