/*

 * RAW GSM demuxer

 * Copyright (c) 2011 Justin Ruggles

 *

 * 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 "libavutil/channel_layout.h"

#include "libavutil/mathematics.h"

#include "libavutil/opt.h"

#include "avformat.h"

#include "demux.h"

#include "internal.h"

#define GSM_BLOCK_SIZE    33

#define GSM_BLOCK_SAMPLES 160

#define GSM_SAMPLE_RATE   8000

typedef struct GSMDemuxerContext {

    AVClass *class;

    int sample_rate;

} GSMDemuxerContext;

static int gsm_probe(const AVProbeData *p)

{

    int valid = 0, invalid = 0;

    uint8_t *b = p->buf;

    while (b < p->buf + p->buf_size - 32) {

        if ((*b & 0xf0) == 0xd0) {

            valid++;

        } else {

            invalid++;

        }

        b += 33;

    }

    if (valid >> 5 > invalid)

        return AVPROBE_SCORE_EXTENSION + 1;

    return 0;

}

static int gsm_read_packet(AVFormatContext *s, AVPacket *pkt)

{

    int ret, size;

    size = GSM_BLOCK_SIZE;

    pkt->pos = avio_tell(s->pb);

    pkt->stream_index = 0;

    ret = av_get_packet(s->pb, pkt, size);

    if (ret < GSM_BLOCK_SIZE) {

        return ret < 0 ? ret : AVERROR(EIO);

    }

    pkt->duration = 1;

    pkt->pts      = pkt->pos / GSM_BLOCK_SIZE;

    return 0;

}

static int gsm_read_header(AVFormatContext *s)

{

    GSMDemuxerContext *c = s->priv_data;

    AVStream *st = avformat_new_stream(s, NULL);

    if (!st)

        return AVERROR(ENOMEM);

    st->codecpar->codec_type  = AVMEDIA_TYPE_AUDIO;

    st->codecpar->codec_id    = AV_CODEC_ID_GSM;

    st->codecpar->ch_layout   = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;

    st->codecpar->sample_rate = c->sample_rate;

    st->codecpar->bit_rate    = GSM_BLOCK_SIZE * 8 * c->sample_rate / GSM_BLOCK_SAMPLES;

    avpriv_set_pts_info(st, 64, GSM_BLOCK_SAMPLES, GSM_SAMPLE_RATE);

    return 0;

}

static const AVOption options[] = {

    { "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),

       AV_OPT_TYPE_INT, {.i64 = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,

       AV_OPT_FLAG_DECODING_PARAM },

    { NULL },

};

static const AVClass gsm_class = {

    .class_name = "gsm demuxer",

    .item_name  = av_default_item_name,

    .option     = options,

    .version    = LIBAVUTIL_VERSION_INT,

};

const FFInputFormat ff_gsm_demuxer = {

    .p.name         = "gsm",

    .p.long_name    = NULL_IF_CONFIG_SMALL("raw GSM"),

    .p.flags        = AVFMT_GENERIC_INDEX,

    .p.extensions   = "gsm",

    .p.priv_class   = &gsm_class,

    .priv_data_size = sizeof(GSMDemuxerContext),

    .read_probe     = gsm_probe,

    .read_header    = gsm_read_header,

    .read_packet    = gsm_read_packet,

    .raw_codec_id   = AV_CODEC_ID_GSM,

};