/*
  * 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 "libavutil/ffmath.h"

 #include "libavutil/intreadwrite.h"

 #include "avcodec.h"
 #include "celp_filters.h"

 #include "internal.h"

 #include "libavutil/lfg.h"
 
 typedef struct CNGContext {
     float *refl_coef, *target_refl_coef;
     float *lpc_coef;
     int order;
     int energy, target_energy;

     int inited;

     float *filter_out;
     float *excitation;
     AVLFG lfg;
 } CNGContext;
 
 static av_cold int cng_decode_close(AVCodecContext *avctx)
 {
     CNGContext *p = avctx->priv_data;

     av_freep(&p->refl_coef);
     av_freep(&p->target_refl_coef);
     av_freep(&p->lpc_coef);
     av_freep(&p->filter_out);
     av_freep(&p->excitation);

     return 0;
 }
 
 static av_cold int cng_decode_init(AVCodecContext *avctx)
 {
     CNGContext *p = avctx->priv_data;
 
     avctx->sample_fmt  = AV_SAMPLE_FMT_S16;
     avctx->channels    = 1;
     avctx->sample_rate = 8000;
 
     p->order            = 12;
     avctx->frame_size   = 640;

     p->refl_coef        = av_mallocz_array(p->order, sizeof(*p->refl_coef));
     p->target_refl_coef = av_mallocz_array(p->order, sizeof(*p->target_refl_coef));
     p->lpc_coef         = av_mallocz_array(p->order, sizeof(*p->lpc_coef));
     p->filter_out       = av_mallocz_array(avctx->frame_size + p->order,

                                      sizeof(*p->filter_out));

     p->excitation       = av_mallocz_array(avctx->frame_size, sizeof(*p->excitation));

     if (!p->refl_coef || !p->target_refl_coef || !p->lpc_coef ||
         !p->filter_out || !p->excitation) {
         cng_decode_close(avctx);
         return AVERROR(ENOMEM);
     }
 
     av_lfg_init(&p->lfg, 0);
 
     return 0;
 }
 
 static void make_lpc_coefs(float *lpc, const float *refl, int order)
 {
     float buf[100];
     float *next, *cur;
     int m, i;
     next = buf;
     cur  = lpc;
     for (m = 0; m < order; m++) {
         next[m] = refl[m];
         for (i = 0; i < m; i++)
             next[i] = cur[i] + refl[m] * cur[m - i - 1];
         FFSWAP(float*, next, cur);
     }
     if (cur != lpc)
         memcpy(lpc, cur, sizeof(*lpc) * order);
 }
 

 static void cng_decode_flush(AVCodecContext *avctx)
 {
     CNGContext *p = avctx->priv_data;
     p->inited = 0;
 }
 

 static int cng_decode_frame(AVCodecContext *avctx, void *data,

                             int *got_frame_ptr, AVPacket *avpkt)

 {

     AVFrame *frame = data;

     CNGContext *p = avctx->priv_data;
     int buf_size  = avpkt->size;
     int ret, i;
     int16_t *buf_out;
     float e = 1.0;
     float scaling;
 
     if (avpkt->size) {

         int dbov = -avpkt->data[0];

         p->target_energy = 1081109975 * ff_exp10(dbov / 10.0) * 0.75;

         memset(p->target_refl_coef, 0, p->order * sizeof(*p->target_refl_coef));

         for (i = 0; i < FFMIN(avpkt->size - 1, p->order); i++) {
             p->target_refl_coef[i] = (avpkt->data[1 + i] - 127) / 128.0;
         }
     }
 

     if (avctx->internal->skip_samples > 10 * avctx->frame_size) {
         avctx->internal->skip_samples = 0;
         return AVERROR_INVALIDDATA;
     }
 

     if (p->inited) {
         p->energy = p->energy / 2 + p->target_energy / 2;
         for (i = 0; i < p->order; i++)
             p->refl_coef[i] = 0.6 *p->refl_coef[i] + 0.4 * p->target_refl_coef[i];
     } else {
         p->energy = p->target_energy;
         memcpy(p->refl_coef, p->target_refl_coef, p->order * sizeof(*p->refl_coef));
         p->inited = 1;
     }

     make_lpc_coefs(p->lpc_coef, p->refl_coef, p->order);

 
     for (i = 0; i < p->order; i++)
         e *= 1.0 - p->refl_coef[i]*p->refl_coef[i];
 
     scaling = sqrt(e * p->energy / 1081109975);
     for (i = 0; i < avctx->frame_size; i++) {
         int r = (av_lfg_get(&p->lfg) & 0xffff) - 0x8000;
         p->excitation[i] = scaling * r;
     }
     ff_celp_lp_synthesis_filterf(p->filter_out + p->order, p->lpc_coef,
                                  p->excitation, avctx->frame_size, p->order);
 

     frame->nb_samples = avctx->frame_size;

     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)

         return ret;

     buf_out = (int16_t *)frame->data[0];

     for (i = 0; i < avctx->frame_size; i++)

         buf_out[i] = av_clip_int16(p->filter_out[i + p->order]);

     memcpy(p->filter_out, p->filter_out + avctx->frame_size,
            p->order * sizeof(*p->filter_out));
 

     *got_frame_ptr = 1;

 
     return buf_size;
 }
 
 AVCodec ff_comfortnoise_decoder = {
     .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_decode_init,
     .decode         = cng_decode_frame,

     .flush          = cng_decode_flush,

     .close          = cng_decode_close,
     .sample_fmts    = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16,
                                                      AV_SAMPLE_FMT_NONE },

     .capabilities   = AV_CODEC_CAP_DR1,

 };