PeerStreamer

/*

 * 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 CodecID *codec)

{

    AACADTSHeaderInfo aac_hdr;

    GetBitContext gbc;

    switch (data_type & 0xff) {

    case IEC61937_AC3:

        *offset = AC3_FRAME_SIZE << 2;

        *codec = CODEC_ID_AC3;

        break;

    case IEC61937_MPEG1_LAYER1:

        *offset = spdif_mpeg_pkt_offset[1][0];

        *codec = CODEC_ID_MP1;

        break;

    case IEC61937_MPEG1_LAYER23:

        *offset = spdif_mpeg_pkt_offset[1][0];

        *codec = CODEC_ID_MP3;

        break;

    case IEC61937_MPEG2_EXT:

        *offset = 4608;

        *codec = CODEC_ID_MP3;

        break;

    case IEC61937_MPEG2_AAC:

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

        if (ff_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 = CODEC_ID_AAC;

        break;

    case IEC61937_MPEG2_LAYER1_LSF:

        *offset = spdif_mpeg_pkt_offset[0][0];

        *codec = CODEC_ID_MP1;

        break;

    case IEC61937_MPEG2_LAYER2_LSF:

        *offset = spdif_mpeg_pkt_offset[0][1];

        *codec = CODEC_ID_MP2;

        break;

    case IEC61937_MPEG2_LAYER3_LSF:

        *offset = spdif_mpeg_pkt_offset[0][2];

        *codec = CODEC_ID_MP3;

        break;

    case IEC61937_DTS1:

        *offset = 2048;

        *codec = CODEC_ID_DTS;

        break;

    case IEC61937_DTS2:

        *offset = 4096;

        *codec = CODEC_ID_DTS;

        break;

    case IEC61937_DTS3:

        *offset = 8192;

        *codec = 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 is", 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)

{

    const uint8_t *buf = p->buf;

    const uint8_t *probe_end = p->buf + FFMIN(2 * SPDIF_MAX_OFFSET, p->buf_size - 1);

    const uint8_t *expected_code = buf + 7;

    uint32_t state = 0;

    int sync_codes = 0;

    int consecutive_codes = 0;

    int offset;

    enum CodecID codec;

    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 + p->buf_size)

                break;

            /* continue probing to find more sync codes */

            probe_end = FFMIN(buf + SPDIF_MAX_OFFSET, p->buf + p->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 + p->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, AVFormatParameters *ap)

{

    s->ctx_flags |= AVFMTCTX_NOHEADER;

    return 0;

}

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

{

    AVIOContext *pb = s->pb;

    enum IEC61937DataType data_type;

    enum CodecID 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_seek(pb, offset - pkt->size - BURST_HEADER_SIZE, SEEK_CUR);

    if (!s->nb_streams) {

        /* first packet, create a stream */

        AVStream *st = av_new_stream(s, 0);

        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 = {

    "spdif",

    NULL_IF_CONFIG_SMALL("IEC 61937 (compressed data in S/PDIF)"),

    0,

    spdif_probe,

    spdif_read_header,

    spdif_read_packet,

    .flags = AVFMT_GENERIC_INDEX,

};