/*

 * 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/mem.h"

#include "avcodec.h"

#include "celp_filters.h"

#include "codec_internal.h"

#include "decode.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;

    av_channel_layout_uninit(&avctx->ch_layout);

    avctx->ch_layout   = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;

    avctx->sample_rate = 8000;

    p->order            = 12;

    avctx->frame_size   = 640;

    p->refl_coef        = av_calloc(p->order, sizeof(*p->refl_coef));

    p->target_refl_coef = av_calloc(p->order, sizeof(*p->target_refl_coef));

    p->lpc_coef         = av_calloc(p->order, sizeof(*p->lpc_coef));

    p->filter_out       = av_calloc(avctx->frame_size + p->order,

                                     sizeof(*p->filter_out));

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

    if (!p->refl_coef || !p->target_refl_coef || !p->lpc_coef ||

        !p->filter_out || !p->excitation) {

        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 av_cold void cng_decode_flush(AVCodecContext *avctx)

{

    CNGContext *p = avctx->priv_data;

    p->inited = 0;

}

static int cng_decode_frame(AVCodecContext *avctx, AVFrame *frame,

                            int *got_frame_ptr, AVPacket *avpkt)

{

    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;

}

const FFCodec ff_comfortnoise_decoder = {

    .p.name         = "comfortnoise",

    CODEC_LONG_NAME("RFC 3389 comfort noise generator"),

    .p.type         = AVMEDIA_TYPE_AUDIO,

    .p.id           = AV_CODEC_ID_COMFORT_NOISE,

    .priv_data_size = sizeof(CNGContext),

    .init           = cng_decode_init,

    FF_CODEC_DECODE_CB(cng_decode_frame),

    .flush          = cng_decode_flush,

    .close          = cng_decode_close,

    CODEC_SAMPLEFMTS(AV_SAMPLE_FMT_S16),

    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_CHANNEL_CONF,

    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,

};