libavformat/spdifdec.c

   1 /*
   2  * IEC 61937 demuxer
   3  * Copyright (c) 2010 Anssi Hannula <anssi.hannula at iki.fi>
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * IEC 61937 demuxer, used for compressed data in S/PDIF
  25  * @author Anssi Hannula
  26  */
  27
  28 #include "libavutil/bswap.h"
  29
  30 #include "libavcodec/ac3.h"
  31 #include "libavcodec/adts_parser.h"
  32
  33 #include "avformat.h"
  34 #include "spdif.h"
  35
  36 static int spdif_get_offset_and_codec(AVFormatContext *s,
  37                                       enum IEC61937DataType data_type,
  38                                       const char *buf, int *offset,
  39                                       enum AVCodecID *codec)
  40 {
  41     uint32_t samples;
  42     uint8_t frames;
  43     int ret;
  44
  45     switch (data_type & 0xff) {
  46     case IEC61937_AC3:
  47         *offset = AC3_FRAME_SIZE << 2;
  48         *codec = AV_CODEC_ID_AC3;
  49         break;
  50     case IEC61937_MPEG1_LAYER1:
  51         *offset = spdif_mpeg_pkt_offset[1][0];
  52         *codec = AV_CODEC_ID_MP1;
  53         break;
  54     case IEC61937_MPEG1_LAYER23:
  55         *offset = spdif_mpeg_pkt_offset[1][0];
  56         *codec = AV_CODEC_ID_MP3;
  57         break;
  58     case IEC61937_MPEG2_EXT:
  59         *offset = 4608;
  60         *codec = AV_CODEC_ID_MP3;
  61         break;
  62     case IEC61937_MPEG2_AAC:
  63         ret = av_adts_header_parse(buf, &samples, &frames);
  64         if (ret < 0) {
  65             if (s) /* be silent during a probe */
  66                 av_log(s, AV_LOG_ERROR, "Invalid AAC packet in IEC 61937\n");
  67             return ret;
  68         }
  69         *offset = samples << 2;
  70         *codec = AV_CODEC_ID_AAC;
  71         break;
  72     case IEC61937_MPEG2_LAYER1_LSF:
  73         *offset = spdif_mpeg_pkt_offset[0][0];
  74         *codec = AV_CODEC_ID_MP1;
  75         break;
  76     case IEC61937_MPEG2_LAYER2_LSF:
  77         *offset = spdif_mpeg_pkt_offset[0][1];
  78         *codec = AV_CODEC_ID_MP2;
  79         break;
  80     case IEC61937_MPEG2_LAYER3_LSF:
  81         *offset = spdif_mpeg_pkt_offset[0][2];
  82         *codec = AV_CODEC_ID_MP3;
  83         break;
  84     case IEC61937_DTS1:
  85         *offset = 2048;
  86         *codec = AV_CODEC_ID_DTS;
  87         break;
  88     case IEC61937_DTS2:
  89         *offset = 4096;
  90         *codec = AV_CODEC_ID_DTS;
  91         break;
  92     case IEC61937_DTS3:
  93         *offset = 8192;
  94         *codec = AV_CODEC_ID_DTS;
  95         break;
  96     default:
  97         if (s) { /* be silent during a probe */
  98             avpriv_request_sample(s, "Data type 0x%04x in IEC 61937",
  99                                   data_type);
 100         }
 101         return AVERROR_PATCHWELCOME;
 102     }
 103     return 0;
 104 }
 105
 106 /* Largest offset between bursts we currently handle, i.e. AAC with
 107    samples = 4096 */
 108 #define SPDIF_MAX_OFFSET 16384
 109
 110 static int spdif_probe(const AVProbeData *p)
 111 {
 112     enum AVCodecID codec;
 113     return ff_spdif_probe (p->buf, p->buf_size, &codec);
 114 }
 115
 116 int ff_spdif_probe(const uint8_t *p_buf, int buf_size, enum AVCodecID *codec)
 117 {
 118     const uint8_t *buf = p_buf;
 119     const uint8_t *probe_end = p_buf + FFMIN(2 * SPDIF_MAX_OFFSET, buf_size - 1);
 120     const uint8_t *expected_code = buf + 7;
 121     uint32_t state = 0;
 122     int sync_codes = 0;
 123     int consecutive_codes = 0;
 124     int offset;
 125
 126     for (; buf < probe_end; buf++) {
 127         state = (state << 8) | *buf;
 128
 129         if (state == (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))
 130                 && buf[1] < 0x37) {
 131             sync_codes++;
 132
 133             if (buf == expected_code) {
 134                 if (++consecutive_codes >= 2)
 135                     return AVPROBE_SCORE_MAX;
 136             } else
 137                 consecutive_codes = 0;
 138
 139             if (buf + 4 + AV_AAC_ADTS_HEADER_SIZE > p_buf + buf_size)
 140                 break;
 141
 142             /* continue probing to find more sync codes */
 143             probe_end = FFMIN(buf + SPDIF_MAX_OFFSET, p_buf + buf_size - 1);
 144
 145             /* skip directly to the next sync code */
 146             if (!spdif_get_offset_and_codec(NULL, (buf[2] << 8) | buf[1],
 147                                             &buf[5], &offset, codec)) {
 148                 if (buf + offset >= p_buf + buf_size)
 149                     break;
 150                 expected_code = buf + offset;
 151                 buf = expected_code - 7;
 152             }
 153         }
 154     }
 155
 156     if (!sync_codes)
 157         return 0;
 158
 159     if (sync_codes >= 6)
 160         /* good amount of sync codes but with unexpected offsets */
 161         return AVPROBE_SCORE_EXTENSION;
 162
 163     /* some sync codes were found */
 164     return AVPROBE_SCORE_EXTENSION / 4;
 165 }
 166
 167 static int spdif_read_header(AVFormatContext *s)
 168 {
 169     s->ctx_flags |= AVFMTCTX_NOHEADER;
 170     return 0;
 171 }
 172
 173 int ff_spdif_read_packet(AVFormatContext *s, AVPacket *pkt)
 174 {
 175     AVIOContext *pb = s->pb;
 176     enum IEC61937DataType data_type;
 177     enum AVCodecID codec_id;
 178     uint32_t state = 0;
 179     int pkt_size_bits, offset, ret;
 180
 181     while (state != (AV_BSWAP16C(SYNCWORD1) << 16 | AV_BSWAP16C(SYNCWORD2))) {
 182         state = (state << 8) | avio_r8(pb);
 183         if (avio_feof(pb))
 184             return AVERROR_EOF;
 185     }
 186
 187     data_type = avio_rl16(pb);
 188     pkt_size_bits = avio_rl16(pb);
 189
 190     if (pkt_size_bits % 16)
 191         avpriv_request_sample(s, "Packet not ending at a 16-bit boundary");
 192
 193     ret = av_new_packet(pkt, FFALIGN(pkt_size_bits, 16) >> 3);
 194     if (ret)
 195         return ret;
 196
 197     pkt->pos = avio_tell(pb) - BURST_HEADER_SIZE;
 198
 199     if (avio_read(pb, pkt->data, pkt->size) < pkt->size) {
 200         return AVERROR_EOF;
 201     }
 202     ff_spdif_bswap_buf16((uint16_t *)pkt->data, (uint16_t *)pkt->data, pkt->size >> 1);
 203
 204     ret = spdif_get_offset_and_codec(s, data_type, pkt->data,
 205                                      &offset, &codec_id);
 206     if (ret < 0) {
 207         return ret;
 208     }
 209
 210     /* skip over the padding to the beginning of the next frame */
 211     avio_skip(pb, offset - pkt->size - BURST_HEADER_SIZE);
 212
 213     if (!s->nb_streams) {
 214         /* first packet, create a stream */
 215         AVStream *st = avformat_new_stream(s, NULL);
 216         if (!st) {
 217             return AVERROR(ENOMEM);
 218         }
 219         st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
 220         st->codecpar->codec_id = codec_id;
 221     } else if (codec_id != s->streams[0]->codecpar->codec_id) {
 222         avpriv_report_missing_feature(s, "Codec change in IEC 61937");
 223         return AVERROR_PATCHWELCOME;
 224     }
 225
 226     if (!s->bit_rate && s->streams[0]->codecpar->sample_rate)
 227         /* stream bitrate matches 16-bit stereo PCM bitrate for currently
 228            supported codecs */
 229         s->bit_rate = 2 * 16LL * s->streams[0]->codecpar->sample_rate;
 230
 231     return 0;
 232 }
 233
 234 AVInputFormat ff_spdif_demuxer = {
 235     .name           = "spdif",
 236     .long_name      = NULL_IF_CONFIG_SMALL("IEC 61937 (compressed data in S/PDIF)"),
 237     .read_probe     = spdif_probe,
 238     .read_header    = spdif_read_header,
 239     .read_packet    = ff_spdif_read_packet,
 240     .flags          = AVFMT_GENERIC_INDEX,
 241 };