/*
  * RAW AC-3 and E-AC-3 demuxer
  * Copyright (c) 2007 Justin Ruggles <justin.ruggles@gmail.com>
  *
  * 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/avassert.h"

 #include "libavutil/crc.h"
 #include "libavcodec/ac3_parser.h"
 #include "avformat.h"

 #include "rawdec.h"

 static int ac3_eac3_probe(AVProbeData *p, enum AVCodecID expected_codec_id)

 {
     int max_frames, first_frames = 0, frames;

     const uint8_t *buf, *buf2, *end;

     enum AVCodecID codec_id = AV_CODEC_ID_AC3;

 
     max_frames = 0;
     buf = p->buf;
     end = buf + p->buf_size;
 
     for(; buf < end; buf++) {

         if(buf > p->buf && !(buf[0] == 0x0B && buf[1] == 0x77)
                         && !(buf[0] == 0x77 && buf[1] == 0x0B) )

             continue;

         buf2 = buf;
 
         for(frames = 0; buf2 < end; frames++) {

             uint8_t buf3[4096];

             uint8_t bitstream_id;
             uint16_t frame_size;

             int i, ret;

             if(!memcmp(buf2, "\x1\x10\0\0\0\0\0\0", 8)) {
                 if (buf2 + 16 > end)
                     break;

                 buf2+=16;

             }

             if (buf[0] == 0x77 && buf[1] == 0x0B) {
                 for(i=0; i<8; i+=2) {

                     buf3[i  ] = buf2[i+1];
                     buf3[i+1] = buf2[i  ];

                 }

                 ret = av_ac3_parse_header(buf3, 8, &bitstream_id,
                                           &frame_size);

             }else

                 ret = av_ac3_parse_header(buf2, end - buf2, &bitstream_id,
                                           &frame_size);

             if (ret < 0)

                 break;

             if(buf2 + frame_size > end)

                 break;
             if (buf[0] == 0x77 && buf[1] == 0x0B) {

                 av_assert0(frame_size <= sizeof(buf3));
                 for(i = 8; i < frame_size; i += 2) {

                     buf3[i  ] = buf2[i+1];
                     buf3[i+1] = buf2[i  ];

                 }

                 if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf3 + 2, frame_size - 2))
                     break;
             } else {
                 if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf2 + 2, frame_size - 2))
                     break;

             }

             if (bitstream_id > 10)

                 codec_id = AV_CODEC_ID_EAC3;

             buf2 += frame_size;

         }
         max_frames = FFMAX(max_frames, frames);
         if(buf == p->buf)
             first_frames = frames;
     }
     if(codec_id != expected_codec_id) return 0;
     // keep this in sync with mp3 probe, both need to avoid
     // issues with MPEG-files!

     if   (first_frames>=7) return AVPROBE_SCORE_EXTENSION + 1;

     else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
     else if(max_frames>=4) return AVPROBE_SCORE_EXTENSION/2;

     else if(max_frames>=1) return 1;
     else                   return 0;
 }
 
 #if CONFIG_AC3_DEMUXER
 static int ac3_probe(AVProbeData *p)
 {

     return ac3_eac3_probe(p, AV_CODEC_ID_AC3);

 }
 

 AVInputFormat ff_ac3_demuxer = {

     .name           = "ac3",
     .long_name      = NULL_IF_CONFIG_SMALL("raw AC-3"),
     .read_probe     = ac3_probe,
     .read_header    = ff_raw_audio_read_header,
     .read_packet    = ff_raw_read_partial_packet,

     .flags= AVFMT_GENERIC_INDEX,
     .extensions = "ac3",

     .raw_codec_id   = AV_CODEC_ID_AC3,

 };
 #endif
 
 #if CONFIG_EAC3_DEMUXER
 static int eac3_probe(AVProbeData *p)
 {

     return ac3_eac3_probe(p, AV_CODEC_ID_EAC3);

 }
 

 AVInputFormat ff_eac3_demuxer = {

     .name           = "eac3",
     .long_name      = NULL_IF_CONFIG_SMALL("raw E-AC-3"),
     .read_probe     = eac3_probe,
     .read_header    = ff_raw_audio_read_header,
     .read_packet    = ff_raw_read_partial_packet,

     .flags          = AVFMT_GENERIC_INDEX,
     .extensions     = "eac3",

     .raw_codec_id   = AV_CODEC_ID_EAC3,

 };
 #endif