/*
  * RFC 3389 comfort noise generator
  * Copyright (c) 2012 Martin Storsjo
  *

  * This file is part of FFmpeg.

  *

  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *

  * FFmpeg is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include <math.h>
 
 #include "libavutil/common.h"
 #include "avcodec.h"
 #include "internal.h"
 #include "lpc.h"
 
 typedef struct CNGContext {
     LPCContext lpc;
     int order;
     int32_t *samples32;
     double *ref_coef;
 } CNGContext;
 
 static av_cold int cng_encode_close(AVCodecContext *avctx)
 {
     CNGContext *p = avctx->priv_data;
     ff_lpc_end(&p->lpc);
     av_free(p->samples32);
     av_free(p->ref_coef);
     return 0;
 }
 
 static av_cold int cng_encode_init(AVCodecContext *avctx)
 {
     CNGContext *p = avctx->priv_data;
     int ret;
 
     if (avctx->channels != 1) {
         av_log(avctx, AV_LOG_ERROR, "Only mono supported\n");
         return AVERROR(EINVAL);
     }
 
     avctx->frame_size = 640;
     p->order = 10;
     if ((ret = ff_lpc_init(&p->lpc, avctx->frame_size, p->order, FF_LPC_TYPE_LEVINSON)) < 0)
         return ret;

     p->samples32 = av_malloc_array(avctx->frame_size, sizeof(*p->samples32));
     p->ref_coef = av_malloc_array(p->order, sizeof(*p->ref_coef));

     if (!p->samples32 || !p->ref_coef) {
         cng_encode_close(avctx);
         return AVERROR(ENOMEM);
     }
 
     return 0;
 }
 
 static int cng_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,

                             const AVFrame *frame, int *got_packet_ptr)

 {
     CNGContext *p = avctx->priv_data;
     int ret, i;
     double energy = 0;
     int qdbov;
     int16_t *samples = (int16_t*) frame->data[0];
 
     if ((ret = ff_alloc_packet(avpkt, 1 + p->order))) {
         av_log(avctx, AV_LOG_ERROR, "Error getting output packet\n");
         return ret;
     }
 
     for (i = 0; i < frame->nb_samples; i++) {
         p->samples32[i] = samples[i];
         energy += samples[i] * samples[i];
     }
     energy /= frame->nb_samples;
     if (energy > 0) {
         double dbov = 10 * log10(energy / 1081109975);
         qdbov = av_clip(-floor(dbov), 0, 127);
     } else {
         qdbov = 127;
     }
     ret = ff_lpc_calc_ref_coefs(&p->lpc, p->samples32, p->order, p->ref_coef);
     avpkt->data[0] = qdbov;
     for (i = 0; i < p->order; i++)
         avpkt->data[1 + i] = p->ref_coef[i] * 127 + 127;
 
     *got_packet_ptr = 1;
     avpkt->size = 1 + p->order;
 
     return 0;
 }
 
 AVCodec ff_comfortnoise_encoder = {
     .name           = "comfortnoise",

     .long_name      = NULL_IF_CONFIG_SMALL("RFC 3389 comfort noise generator"),

     .type           = AVMEDIA_TYPE_AUDIO,
     .id             = AV_CODEC_ID_COMFORT_NOISE,
     .priv_data_size = sizeof(CNGContext),
     .init           = cng_encode_init,
     .encode2        = cng_encode_frame,
     .close          = cng_encode_close,
     .sample_fmts    = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
                                                      AV_SAMPLE_FMT_NONE },
 };