mpeg.c.svn-base

mediastreamer2是开源的网络传输媒体流的库

    /* stuffing */
    for(;;) {
        if (len < 1)
            goto error_redo;
        c = get_byte(s->pb);
        len--;
        /* XXX: for mpeg1, should test only bit 7 */
        if (c != 0xff)
            break;
    }
    if ((c & 0xc0) == 0x40) {
        /* buffer scale & size */
        get_byte(s->pb);
        c = get_byte(s->pb);
        len -= 2;
    }
    if ((c & 0xe0) == 0x20) {
        dts = pts = get_pts(s->pb, c);
        len -= 4;
        if (c & 0x10){
            dts = get_pts(s->pb, -1);
            len -= 5;
        }
    } else if ((c & 0xc0) == 0x80) {
        /* mpeg 2 PES */
#if 0 /* some streams have this field set for no apparent reason */
        if ((c & 0x30) != 0) {
            /* Encrypted multiplex not handled */
            goto redo;
        }
#endif
        flags = get_byte(s->pb);
        header_len = get_byte(s->pb);
        len -= 2;
        if (header_len > len)
            goto error_redo;
        len -= header_len;
        if (flags & 0x80) {
            dts = pts = get_pts(s->pb, -1);
            header_len -= 5;
            if (flags & 0x40) {
                dts = get_pts(s->pb, -1);
                header_len -= 5;
            }
        }
        if (flags & 0x01) { /* PES extension */
            pes_ext = get_byte(s->pb);
            header_len--;
            if (pes_ext & 0x40) { /* pack header - should be zero in PS */
                goto error_redo;
            }
            /* Skip PES private data, program packet sequence counter and P-STD buffer */
            skip = (pes_ext >> 4) & 0xb;
            skip += skip & 0x9;
            url_fskip(s->pb, skip);
            header_len -= skip;

            if (pes_ext & 0x01) { /* PES extension 2 */
                ext2_len = get_byte(s->pb);
                header_len--;
                if ((ext2_len & 0x7f) > 0) {
                    id_ext = get_byte(s->pb);
                    if ((id_ext & 0x80) == 0)
                        startcode = ((startcode & 0xff) << 8) | id_ext;
                    header_len--;
                }
            }
        }
        if(header_len < 0)
            goto error_redo;
        url_fskip(s->pb, header_len);
    }
    else if( c!= 0xf )
        goto redo;

    if (startcode == PRIVATE_STREAM_1 && !m->psm_es_type[startcode & 0xff]) {
        startcode = get_byte(s->pb);
        len--;
        if (startcode >= 0x80 && startcode <= 0xcf) {
            /* audio: skip header */
            get_byte(s->pb);
            get_byte(s->pb);
            get_byte(s->pb);
            len -= 3;
            if (startcode >= 0xb0 && startcode <= 0xbf) {
                /* MLP/TrueHD audio has a 4-byte header */
                get_byte(s->pb);
                len--;
            }
        }
    }
    if(len<0)
        goto error_redo;
    if(dts != AV_NOPTS_VALUE && ppos){
        int i;
        for(i=0; i<s->nb_streams; i++){
            if(startcode == s->streams[i]->id &&
               !url_is_streamed(s->pb) /* index useless on streams anyway */) {
                ff_reduce_index(s, i);
                av_add_index_entry(s->streams[i], *ppos, dts, 0, 0, AVINDEX_KEYFRAME /* FIXME keyframe? */);
            }
        }
    }

    *pstart_code = startcode;
    *ppts = pts;
    *pdts = dts;
    return len;
}

static int mpegps_read_packet(AVFormatContext *s,
                              AVPacket *pkt)
{
    MpegDemuxContext *m = s->priv_data;
    AVStream *st;
    int len, startcode, i, type, codec_id = 0, es_type;
    int64_t pts, dts, dummy_pos; //dummy_pos is needed for the index building to work

 redo:
    len = mpegps_read_pes_header(s, &dummy_pos, &startcode, &pts, &dts);
    if (len < 0)
        return len;

    /* now find stream */
    for(i=0;i<s->nb_streams;i++) {
        st = s->streams[i];
        if (st->id == startcode)
            goto found;
    }

    es_type = m->psm_es_type[startcode & 0xff];
    if(es_type > 0){
        if(es_type == STREAM_TYPE_VIDEO_MPEG1){
            codec_id = CODEC_ID_MPEG2VIDEO;
            type = CODEC_TYPE_VIDEO;
        } else if(es_type == STREAM_TYPE_VIDEO_MPEG2){
            codec_id = CODEC_ID_MPEG2VIDEO;
            type = CODEC_TYPE_VIDEO;
        } else if(es_type == STREAM_TYPE_AUDIO_MPEG1 ||
                  es_type == STREAM_TYPE_AUDIO_MPEG2){
            codec_id = CODEC_ID_MP3;
            type = CODEC_TYPE_AUDIO;
        } else if(es_type == STREAM_TYPE_AUDIO_AAC){
            codec_id = CODEC_ID_AAC;
            type = CODEC_TYPE_AUDIO;
        } else if(es_type == STREAM_TYPE_VIDEO_MPEG4){
            codec_id = CODEC_ID_MPEG4;
            type = CODEC_TYPE_VIDEO;
        } else if(es_type == STREAM_TYPE_VIDEO_H264){
            codec_id = CODEC_ID_H264;
            type = CODEC_TYPE_VIDEO;
        } else if(es_type == STREAM_TYPE_AUDIO_AC3){
            codec_id = CODEC_ID_AC3;
            type = CODEC_TYPE_AUDIO;
        } else {
            goto skip;
        }
    } else if (startcode >= 0x1e0 && startcode <= 0x1ef) {
        static const unsigned char avs_seqh[4] = { 0, 0, 1, 0xb0 };
        unsigned char buf[8];
        get_buffer(s->pb, buf, 8);
        url_fseek(s->pb, -8, SEEK_CUR);
        if(!memcmp(buf, avs_seqh, 4) && (buf[6] != 0 || buf[7] != 1))
            codec_id = CODEC_ID_CAVS;
        else
            codec_id = CODEC_ID_MPEG2VIDEO;
        type = CODEC_TYPE_VIDEO;
    } else if (startcode >= 0x1c0 && startcode <= 0x1df) {
        type = CODEC_TYPE_AUDIO;
        codec_id = m->sofdec > 0 ? CODEC_ID_ADPCM_ADX : CODEC_ID_MP2;
    } else if (startcode >= 0x80 && startcode <= 0x87) {
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_AC3;
    } else if ((startcode >= 0x88 && startcode <= 0x8f)
               ||( startcode >= 0x98 && startcode <= 0x9f)) {
        /* 0x90 - 0x97 is reserved for SDDS in DVD specs */
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_DTS;
    } else if (startcode >= 0xa0 && startcode <= 0xaf) {
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_PCM_S16BE;
    } else if (startcode >= 0xb0 && startcode <= 0xbf) {
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_MLP;
    } else if (startcode >= 0xc0 && startcode <= 0xcf) {
        /* Used for both AC-3 and E-AC-3 in EVOB files */
        type = CODEC_TYPE_AUDIO;
        codec_id = CODEC_ID_AC3;
    } else if (startcode >= 0x20 && startcode <= 0x3f) {
        type = CODEC_TYPE_SUBTITLE;
        codec_id = CODEC_ID_DVD_SUBTITLE;
    } else if (startcode >= 0xfd55 && startcode <= 0xfd5f) {
        type = CODEC_TYPE_VIDEO;
        codec_id = CODEC_ID_VC1;
    } else {
    skip:
        /* skip packet */
        url_fskip(s->pb, len);
        goto redo;
    }
    /* no stream found: add a new stream */
    st = av_new_stream(s, startcode);
    if (!st)
        goto skip;
    st->codec->codec_type = type;
    st->codec->codec_id = codec_id;
    if (codec_id != CODEC_ID_PCM_S16BE)
        st->need_parsing = AVSTREAM_PARSE_FULL;
 found:
    if(st->discard >= AVDISCARD_ALL)
        goto skip;
    if (startcode >= 0xa0 && startcode <= 0xaf) {
        int b1, freq;

        /* for LPCM, we just skip the header and consider it is raw
           audio data */
        if (len <= 3)
            goto skip;
        get_byte(s->pb); /* emphasis (1), muse(1), reserved(1), frame number(5) */
        b1 = get_byte(s->pb); /* quant (2), freq(2), reserved(1), channels(3) */
        get_byte(s->pb); /* dynamic range control (0x80 = off) */
        len -= 3;
        freq = (b1 >> 4) & 3;
        st->codec->sample_rate = lpcm_freq_tab[freq];
        st->codec->channels = 1 + (b1 & 7);
        st->codec->bit_rate = st->codec->channels * st->codec->sample_rate * 2;
    }
    av_new_packet(pkt, len);
    get_buffer(s->pb, pkt->data, pkt->size);
    pkt->pts = pts;
    pkt->dts = dts;
    pkt->stream_index = st->index;
#if 0
    av_log(s, AV_LOG_DEBUG, "%d: pts=%0.3f dts=%0.3f size=%d\n",
           pkt->stream_index, pkt->pts / 90000.0, pkt->dts / 90000.0, pkt->size);
#endif

    return 0;
}

static int mpegps_read_close(AVFormatContext *s)
{
    return 0;
}

static int64_t mpegps_read_dts(AVFormatContext *s, int stream_index,
                               int64_t *ppos, int64_t pos_limit)
{
    int len, startcode;
    int64_t pos, pts, dts;

    pos = *ppos;
#ifdef DEBUG_SEEK
    printf("read_dts: pos=0x%"PRIx64" next=%d -> ", pos, find_next);
#endif
    url_fseek(s->pb, pos, SEEK_SET);
    for(;;) {
        len = mpegps_read_pes_header(s, &pos, &startcode, &pts, &dts);
        if (len < 0) {
#ifdef DEBUG_SEEK
            printf("none (ret=%d)\n", len);
#endif
            return AV_NOPTS_VALUE;
        }
        if (startcode == s->streams[stream_index]->id &&
            dts != AV_NOPTS_VALUE) {
            break;
        }
        url_fskip(s->pb, len);
    }
#ifdef DEBUG_SEEK
    printf("pos=0x%"PRIx64" dts=0x%"PRIx64" %0.3f\n", pos, dts, dts / 90000.0);
#endif
    *ppos = pos;
    return dts;
}

AVInputFormat mpegps_demuxer = {
    "mpeg",
    "MPEG PS format",
    sizeof(MpegDemuxContext),
    mpegps_probe,
    mpegps_read_header,
    mpegps_read_packet,
    mpegps_read_close,
    NULL, //mpegps_read_seek,
    mpegps_read_dts,
    .flags = AVFMT_SHOW_IDS,
};