/*
  * 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 "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(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) {

         av_packet_unref(pkt);

         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    = s->iformat->raw_codec_id;
     st->codecpar->channels    = 1;
     st->codecpar->channel_layout = AV_CH_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,
 };
 
 AVInputFormat ff_gsm_demuxer = {
     .name           = "gsm",
     .long_name      = NULL_IF_CONFIG_SMALL("raw GSM"),
     .priv_data_size = sizeof(GSMDemuxerContext),

     .read_probe     = gsm_probe,

     .read_header    = gsm_read_header,
     .read_packet    = gsm_read_packet,

     .flags          = AVFMT_GENERIC_INDEX,

     .extensions     = "gsm",

     .raw_codec_id   = AV_CODEC_ID_GSM,

     .priv_class     = &gsm_class,

 };