mpegts.c

static int mpegts_read_header(AVFormatContext *s,
                              AVFormatParameters *ap)
{
    MpegTSContext *ts = s->priv_data;
    ByteIOContext *pb = &s->pb;
    uint8_t buf[1024];
    int len, sid;
    int64_t pos;
    MpegTSService *service;
    
    if (ap) {
        ts->mpeg2ts_raw = ap->mpeg2ts_raw;
        ts->mpeg2ts_compute_pcr = ap->mpeg2ts_compute_pcr;
    }

    /* read the first 1024 bytes to get packet size */
    pos = url_ftell(pb);
    len = get_buffer(pb, buf, sizeof(buf));
    if (len != sizeof(buf))
        goto fail;
    ts->raw_packet_size = get_packet_size(buf, sizeof(buf));
    if (ts->raw_packet_size <= 0)
        goto fail;
    ts->stream = s;
    ts->auto_guess = 0;

    if (!ts->mpeg2ts_raw) {
        /* normal demux */

        if (!ts->auto_guess) {
            ts->set_service_ret = -1;

            /* first do a scaning to get all the services */
            url_fseek(pb, pos, SEEK_SET);
            mpegts_scan_sdt(ts);
            
            handle_packets(ts, MAX_SCAN_PACKETS);
            
            if (ts->nb_services <= 0) {
                /* no SDT found, we try to look at the PAT */
                
                /* First remove the SDT filters from each PID */
                int i;
                for (i=0; i < NB_PID_MAX; i++) {
                    if (ts->pids[i])
                        mpegts_close_filter(ts, ts->pids[i]);
                }
                url_fseek(pb, pos, SEEK_SET);
                mpegts_scan_pat(ts);
                
                handle_packets(ts, MAX_SCAN_PACKETS);
            }
            
            if (ts->nb_services <= 0)
                return -1;
            
            /* tune to first service found */
            service = ts->services[0];
            sid = service->sid;
#ifdef DEBUG_SI
            printf("tuning to '%s'\n", service->name);
#endif
            
            /* now find the info for the first service if we found any,
               otherwise try to filter all PATs */
            
            url_fseek(pb, pos, SEEK_SET);
            mpegts_set_service(ts, sid, set_service_cb, ts);
            
            handle_packets(ts, MAX_SCAN_PACKETS);
            
            /* if could not find service, exit */
            if (ts->set_service_ret != 0)
                return -1;
            
#ifdef DEBUG_SI
            printf("tuning done\n");
#endif
        }
        s->ctx_flags |= AVFMTCTX_NOHEADER;
    } else {
        AVStream *st;
        int pcr_pid, pid, nb_packets, nb_pcrs, ret, pcr_l;
        int64_t pcrs[2], pcr_h;
        int packet_count[2];
        uint8_t packet[TS_PACKET_SIZE];
        
        /* only read packets */

        s->pts_num = 1;
        s->pts_den = 27000000;
        
        st = av_new_stream(s, 0);
        if (!st)
            goto fail;
        st->codec.codec_type = CODEC_TYPE_DATA;
        st->codec.codec_id = CODEC_ID_MPEG2TS;
        
        /* we iterate until we find two PCRs to estimate the bitrate */
        pcr_pid = -1;
        nb_pcrs = 0;
        nb_packets = 0;
        for(;;) {
            ret = read_packet(&s->pb, packet, ts->raw_packet_size);
            if (ret < 0)
                return -1;
            pid = ((packet[1] & 0x1f) << 8) | packet[2];
            if ((pcr_pid == -1 || pcr_pid == pid) &&
                parse_pcr(&pcr_h, &pcr_l, packet) == 0) {
                pcr_pid = pid;
                packet_count[nb_pcrs] = nb_packets;
                pcrs[nb_pcrs] = pcr_h * 300 + pcr_l;
                nb_pcrs++;
                if (nb_pcrs >= 2)
                    break;
            }
            nb_packets++;
        }

        /* NOTE1: the bitrate is computed without the FEC */
        /* NOTE2: it is only the bitrate of the start of the stream */
        ts->pcr_incr = (pcrs[1] - pcrs[0]) / (packet_count[1] - packet_count[0]);
        ts->cur_pcr = pcrs[0] - ts->pcr_incr * packet_count[0];
        s->bit_rate = (TS_PACKET_SIZE * 8) * 27e6 / ts->pcr_incr;
        st->codec.bit_rate = s->bit_rate;
        st->start_time = ts->cur_pcr * 1000000.0 / 27.0e6;
#if 0
        printf("start=%0.3f pcr=%0.3f incr=%d\n",
               st->start_time / 1000000.0, pcrs[0] / 27e6, ts->pcr_incr);
#endif
    }

    url_fseek(pb, pos, SEEK_SET);
    return 0;
 fail:
    return -1;
}

#define MAX_PACKET_READAHEAD ((128 * 1024) / 188)

static int mpegts_raw_read_packet(AVFormatContext *s,
                                  AVPacket *pkt)
{
    MpegTSContext *ts = s->priv_data;
    int ret, i;
    int64_t pcr_h, next_pcr_h, pos;
    int pcr_l, next_pcr_l;
    uint8_t pcr_buf[12];

    if (av_new_packet(pkt, TS_PACKET_SIZE) < 0)
        return -ENOMEM;
    ret = read_packet(&s->pb, pkt->data, ts->raw_packet_size);
    if (ret < 0) {
        av_free_packet(pkt);
        return ret;
    }
    if (ts->mpeg2ts_compute_pcr) {
        /* compute exact PCR for each packet */
        if (parse_pcr(&pcr_h, &pcr_l, pkt->data) == 0) {
            /* we read the next PCR (XXX: optimize it by using a bigger buffer */
            pos = url_ftell(&s->pb);
            for(i = 0; i < MAX_PACKET_READAHEAD; i++) {
                url_fseek(&s->pb, pos + i * ts->raw_packet_size, SEEK_SET);
                get_buffer(&s->pb, pcr_buf, 12);
                if (parse_pcr(&next_pcr_h, &next_pcr_l, pcr_buf) == 0) {
                    /* XXX: not precise enough */
                    ts->pcr_incr = ((next_pcr_h - pcr_h) * 300 + (next_pcr_l - pcr_l)) / 
                        (i + 1);
                    break;
                }
            }
            url_fseek(&s->pb, pos, SEEK_SET);
            /* no next PCR found: we use previous increment */
            ts->cur_pcr = pcr_h * 300 + pcr_l;
        }
        pkt->pts = ts->cur_pcr;
        pkt->duration = ts->pcr_incr;
        ts->cur_pcr += ts->pcr_incr;
    }
    pkt->stream_index = 0;
    return 0;
}

static int mpegts_read_packet(AVFormatContext *s,
                              AVPacket *pkt)
{
    MpegTSContext *ts = s->priv_data;

    if (!ts->mpeg2ts_raw) {
        ts->pkt = pkt;
        return handle_packets(ts, 0);
    } else {
        return mpegts_raw_read_packet(s, pkt);
    }
}

static int mpegts_read_close(AVFormatContext *s)
{
    MpegTSContext *ts = s->priv_data;
    int i;
    for(i=0;i<NB_PID_MAX;i++)
        av_free(ts->pids[i]);
    return 0;
}

/**************************************************************/
/* parsing functions - called from other demuxers such as RTP */

MpegTSContext *mpegts_parse_open(AVFormatContext *s)
{
    MpegTSContext *ts;
    
    ts = av_mallocz(sizeof(MpegTSContext));
    if (!ts)
        return NULL;
    /* no stream case, currently used by RTP */
    ts->raw_packet_size = TS_PACKET_SIZE;
    ts->stream = s;
    ts->auto_guess = 1;
    return ts;
}

/* return the consumed length if a packet was output, or -1 if no
   packet is output */
int mpegts_parse_packet(MpegTSContext *ts, AVPacket *pkt,
                        const uint8_t *buf, int len)
{
    int len1;

    len1 = len;
    ts->pkt = pkt;
    ts->stop_parse = 0;
    for(;;) {
        if (ts->stop_parse)
            break;
        if (len < TS_PACKET_SIZE)
            return -1;
        if (buf[0] != 0x47) {
            buf--;
            len--;
        } else {
            handle_packet(ts, buf);
            buf += TS_PACKET_SIZE;
            len -= TS_PACKET_SIZE;
        }
    }
    return len1 - len;
}

void mpegts_parse_close(MpegTSContext *ts)
{
    int i;

    for(i=0;i<NB_PID_MAX;i++)
        av_free(ts->pids[i]);
    av_free(ts);
}

AVInputFormat mpegts_demux = {
    "mpegts",
    "MPEG2 transport stream format",
    sizeof(MpegTSContext),
    mpegts_probe,
    mpegts_read_header,
    mpegts_read_packet,
    mpegts_read_close,
    .flags = AVFMT_SHOW_IDS,
};

int mpegts_init(void)
{
    av_register_input_format(&mpegts_demux);
#ifdef CONFIG_ENCODERS
    av_register_output_format(&mpegts_mux);
#endif
    return 0;
}