Function dash_write_packet

libavformat/dashenc.c:1941–2165

}

static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    DASHContext *c = s->priv_data;
    AVStream *st = s->streams[pkt->stream_index];
    OutputStream *os = &c->streams[pkt->stream_index];
    AdaptationSet *as = &c->as[os->as_idx - 1];
    int64_t seg_end_duration, elapsed_duration;
    int ret;

    ret = update_stream_extradata(s, os, pkt, &st->avg_frame_rate);
    if (ret < 0)
        return ret;

    // Fill in a heuristic guess of the packet duration, if none is available.
    // The mp4 muxer will do something similar (for the last packet in a fragment)
    // if nothing is set (setting it for the other packets doesn't hurt).
    // By setting a nonzero duration here, we can be sure that the mp4 muxer won't
    // invoke its heuristic (this doesn't have to be identical to that algorithm),
    // so that we know the exact timestamps of fragments.
    if (!pkt->duration && os->last_dts != AV_NOPTS_VALUE)
        pkt->duration = pkt->dts - os->last_dts;
    os->last_dts = pkt->dts;

    // If forcing the stream to start at 0, the mp4 muxer will set the start
    // timestamps to 0. Do the same here, to avoid mismatches in duration/timestamps.
    if (os->first_pts == AV_NOPTS_VALUE &&
        s->avoid_negative_ts == AVFMT_AVOID_NEG_TS_MAKE_ZERO) {
        pkt->pts -= pkt->dts;
        pkt->dts  = 0;
    }

    if (c->write_prft) {
        ret = dash_parse_prft(c, pkt);
        if (ret < 0)
            return ret;
    }

    if (os->first_pts == AV_NOPTS_VALUE) {
        os->first_pts = pkt->pts;
    }
    os->last_pts = pkt->pts;

    if (!c->availability_start_time[0]) {
        int64_t start_time_us = av_gettime();
        c->start_time_s = start_time_us / 1000000;
        format_date(c->availability_start_time,
                    sizeof(c->availability_start_time), start_time_us);
    }

    if (!os->packets_written)
        os->availability_time_offset = 0;

    if (!os->availability_time_offset &&
        ((os->frag_type == FRAG_TYPE_DURATION && os->seg_duration != os->frag_duration) ||
         (os->frag_type == FRAG_TYPE_EVERY_FRAME && pkt->duration))) {
        AdaptationSet *as = &c->as[os->as_idx - 1];
        int64_t frame_duration = 0;