/*
  * IEC 61937 demuxer
  * Copyright (c) 2010 Anssi Hannula <anssi.hannula at iki.fi>
  *
  * 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
  */
 
 /**
  * @file
  * IEC 61937 demuxer, used for compressed data in S/PDIF
  * @author Anssi Hannula
  */
 
 #include "avformat.h"
 #include "spdif.h"
 #include "libavcodec/ac3.h"
 #include "libavcodec/aacadtsdec.h"
 
 static int spdif_get_offset_and_codec(AVFormatContext *s,

                                       enum IEC61937DataType data_type,

                                       const char *buf, int *offset,

                                       enum AVCodecID *codec)

 {
     AACADTSHeaderInfo aac_hdr;
     GetBitContext gbc;
 
     switch (data_type & 0xff) {

     case IEC61937_AC3:

         *offset = AC3_FRAME_SIZE << 2;

         *codec = AV_CODEC_ID_AC3;

         break;

     case IEC61937_MPEG1_LAYER1:

         *offset = spdif_mpeg_pkt_offset[1][0];

         *codec = AV_CODEC_ID_MP1;

         break;

     case IEC61937_MPEG1_LAYER23:

         *offset = spdif_mpeg_pkt_offset[1][0];

         *codec = AV_CODEC_ID_MP3;

         break;

     case IEC61937_MPEG2_EXT:

         *offset = 4608;

         *codec = AV_CODEC_ID_MP3;

         break;

     case IEC61937_MPEG2_AAC:

         init_get_bits(&gbc, buf, AAC_ADTS_HEADER_SIZE * 8);

         if (avpriv_aac_parse_header(&gbc, &aac_hdr)) {

             if (s) /* be silent during a probe */
                 av_log(s, AV_LOG_ERROR, "Invalid AAC packet in IEC 61937\n");
             return AVERROR_INVALIDDATA;
         }
         *offset = aac_hdr.samples << 2;

         *codec = AV_CODEC_ID_AAC;

         break;

     case IEC61937_MPEG2_LAYER1_LSF:

         *offset = spdif_mpeg_pkt_offset[0][0];

         *codec = AV_CODEC_ID_MP1;

         break;

     case IEC61937_MPEG2_LAYER2_LSF:

         *offset = spdif_mpeg_pkt_offset[0][1];

         *codec = AV_CODEC_ID_MP2;

         break;

     case IEC61937_MPEG2_LAYER3_LSF:

         *offset = spdif_mpeg_pkt_offset[0][2];

         *codec = AV_CODEC_ID_MP3;

         break;

     case IEC61937_DTS1:

         *offset = 2048;

         *codec = AV_CODEC_ID_DTS;

         break;

     case IEC61937_DTS2:

         *offset = 4096;

         *codec = AV_CODEC_ID_DTS;

         break;

     case IEC61937_DTS3:

         *offset = 8192;

         *codec = AV_CODEC_ID_DTS;

         break;
     default:
         if (s) { /* be silent during a probe */
             av_log(s, AV_LOG_WARNING, "Data type 0x%04x", data_type);

             av_log_missing_feature(s, " in IEC 61937", 1);

         }
         return AVERROR_PATCHWELCOME;
     }
     return 0;
 }
 
 /* Largest offset between bursts we currently handle, i.e. AAC with
    aac_hdr.samples = 4096 */
 #define SPDIF_MAX_OFFSET 16384
 
 static int spdif_probe(AVProbeData *p)
 {

     enum AVCodecID codec;
     return ff_spdif_probe (p->buf, p->buf_size, &codec);
 }
 
 int ff_spdif_probe(const uint8_t *p_buf, int buf_size, enum AVCodecID *codec)
 {
     const uint8_t *buf = p_buf;
     const uint8_t *probe_end = p_buf + FFMIN(2 * SPDIF_MAX_OFFSET, buf_size - 1);

     const uint8_t *expected_code = buf + 7;
     uint32_t state = 0;
     int sync_codes = 0;
     int consecutive_codes = 0;
     int offset;
 
     for (; buf < probe_end; buf++) {
         state = (state << 8) | *buf;
 
         if (state == (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))
                 && buf[1] < 0x37) {
             sync_codes++;
 
             if (buf == expected_code) {
                 if (++consecutive_codes >= 2)
                     return AVPROBE_SCORE_MAX;
             } else
                 consecutive_codes = 0;
 

             if (buf + 4 + AAC_ADTS_HEADER_SIZE > p_buf + buf_size)

                 break;
 
             /* continue probing to find more sync codes */

             probe_end = FFMIN(buf + SPDIF_MAX_OFFSET, p_buf + buf_size - 1);

 
             /* skip directly to the next sync code */
             if (!spdif_get_offset_and_codec(NULL, (buf[2] << 8) | buf[1],

                                             &buf[5], &offset, codec)) {
                 if (buf + offset >= p_buf + buf_size)

                     break;
                 expected_code = buf + offset;
                 buf = expected_code - 7;
             }
         }
     }
 
     if (!sync_codes)
         return 0;
 
     if (sync_codes >= 6)
         /* good amount of sync codes but with unexpected offsets */
         return AVPROBE_SCORE_MAX / 2;
 
     /* some sync codes were found */
     return AVPROBE_SCORE_MAX / 8;
 }
 

 static int spdif_read_header(AVFormatContext *s)

 {
     s->ctx_flags |= AVFMTCTX_NOHEADER;
     return 0;
 }
 

 int ff_spdif_read_packet(AVFormatContext *s, AVPacket *pkt)

 {

     AVIOContext *pb = s->pb;

     enum IEC61937DataType data_type;

     enum AVCodecID codec_id;

     uint32_t state = 0;
     int pkt_size_bits, offset, ret;
 
     while (state != (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))) {

         state = (state << 8) | avio_r8(pb);

         if (url_feof(pb))
             return AVERROR_EOF;
     }
 

     data_type = avio_rl16(pb);
     pkt_size_bits = avio_rl16(pb);

 
     if (pkt_size_bits % 16)
         av_log_ask_for_sample(s, "Packet does not end to a 16-bit boundary.");
 
     ret = av_new_packet(pkt, FFALIGN(pkt_size_bits, 16) >> 3);
     if (ret)
         return ret;
 

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

     if (avio_read(pb, pkt->data, pkt->size) < pkt->size) {

         av_free_packet(pkt);
         return AVERROR_EOF;
     }
     ff_spdif_bswap_buf16((uint16_t *)pkt->data, (uint16_t *)pkt->data, pkt->size >> 1);
 
     ret = spdif_get_offset_and_codec(s, data_type, pkt->data,
                                      &offset, &codec_id);
     if (ret) {
         av_free_packet(pkt);
         return ret;
     }
 
     /* skip over the padding to the beginning of the next frame */

     avio_skip(pb, offset - pkt->size - BURST_HEADER_SIZE);

 
     if (!s->nb_streams) {
         /* first packet, create a stream */

         AVStream *st = avformat_new_stream(s, NULL);

         if (!st) {
             av_free_packet(pkt);
             return AVERROR(ENOMEM);
         }
         st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
         st->codec->codec_id = codec_id;
     } else if (codec_id != s->streams[0]->codec->codec_id) {

         av_log_missing_feature(s, "Codec change in IEC 61937", 0);

         return AVERROR_PATCHWELCOME;
     }
 
     if (!s->bit_rate && s->streams[0]->codec->sample_rate)
         /* stream bitrate matches 16-bit stereo PCM bitrate for currently
            supported codecs */
         s->bit_rate = 2 * 16 * s->streams[0]->codec->sample_rate;
 
     return 0;
 }
 

 AVInputFormat ff_spdif_demuxer = {

     .name           = "spdif",
     .long_name      = NULL_IF_CONFIG_SMALL("IEC 61937 (compressed data in S/PDIF)"),
     .read_probe     = spdif_probe,
     .read_header    = spdif_read_header,

     .read_packet    = ff_spdif_read_packet,

     .flags          = AVFMT_GENERIC_INDEX,

 };