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 "internal.h"
yading@10: #include "lpc.h"
yading@10: 
yading@10: typedef struct CNGContext {
yading@10:     LPCContext lpc;
yading@10:     int order;
yading@10:     int32_t *samples32;
yading@10:     double *ref_coef;
yading@10: } CNGContext;
yading@10: 
yading@10: static av_cold int cng_encode_close(AVCodecContext *avctx)
yading@10: {
yading@10:     CNGContext *p = avctx->priv_data;
yading@10:     ff_lpc_end(&p->lpc);
yading@10:     av_free(p->samples32);
yading@10:     av_free(p->ref_coef);
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static av_cold int cng_encode_init(AVCodecContext *avctx)
yading@10: {
yading@10:     CNGContext *p = avctx->priv_data;
yading@10:     int ret;
yading@10: 
yading@10:     if (avctx->channels != 1) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Only mono supported\n");
yading@10:         return AVERROR(EINVAL);
yading@10:     }
yading@10: 
yading@10:     avctx->frame_size = 640;
yading@10:     p->order = 10;
yading@10:     if ((ret = ff_lpc_init(&p->lpc, avctx->frame_size, p->order, FF_LPC_TYPE_LEVINSON)) < 0)
yading@10:         return ret;
yading@10:     p->samples32 = av_malloc(avctx->frame_size * sizeof(*p->samples32));
yading@10:     p->ref_coef = av_malloc(p->order * sizeof(*p->ref_coef));
yading@10:     if (!p->samples32 || !p->ref_coef) {
yading@10:         cng_encode_close(avctx);
yading@10:         return AVERROR(ENOMEM);
yading@10:     }
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: static int cng_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
yading@10:                             const AVFrame *frame, int *got_packet_ptr)
yading@10: {
yading@10:     CNGContext *p = avctx->priv_data;
yading@10:     int ret, i;
yading@10:     double energy = 0;
yading@10:     int qdbov;
yading@10:     int16_t *samples = (int16_t*) frame->data[0];
yading@10: 
yading@10:     if ((ret = ff_alloc_packet(avpkt, 1 + p->order))) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Error getting output packet\n");
yading@10:         return ret;
yading@10:     }
yading@10: 
yading@10:     for (i = 0; i < frame->nb_samples; i++) {
yading@10:         p->samples32[i] = samples[i];
yading@10:         energy += samples[i] * samples[i];
yading@10:     }
yading@10:     energy /= frame->nb_samples;
yading@10:     if (energy > 0) {
yading@10:         double dbov = 10 * log10(energy / 1081109975);
yading@10:         qdbov = av_clip(-floor(dbov), 0, 127);
yading@10:     } else {
yading@10:         qdbov = 127;
yading@10:     }
yading@10:     ret = ff_lpc_calc_ref_coefs(&p->lpc, p->samples32, p->order, p->ref_coef);
yading@10:     avpkt->data[0] = qdbov;
yading@10:     for (i = 0; i < p->order; i++)
yading@10:         avpkt->data[1 + i] = p->ref_coef[i] * 127 + 127;
yading@10: 
yading@10:     *got_packet_ptr = 1;
yading@10:     avpkt->size = 1 + p->order;
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: AVCodec ff_comfortnoise_encoder = {
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_encode_init,
yading@10:     .encode2        = cng_encode_frame,
yading@10:     .close          = cng_encode_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: };