Function overflow_heartbeat

fftools/sync_queue.c:272–331

If the queue for the given stream (or all streams when stream_idx=-1) * is overflowing, trigger a fake heartbeat on lagging streams. * * @return 1 if heartbeat triggered, 0 otherwise */

 * @return 1 if heartbeat triggered, 0 otherwise
 */
static int overflow_heartbeat(SyncQueue *sq, int stream_idx)
{
    SyncQueueStream *st;
    SyncQueueFrame frame;
    int64_t tail_ts = AV_NOPTS_VALUE;

    /* if no stream specified, pick the one that is most ahead */
    if (stream_idx < 0) {
        int64_t ts = AV_NOPTS_VALUE;

        for (int i = 0; i < sq->nb_streams; i++) {
            st = &sq->streams[i];
            if (st->head_ts != AV_NOPTS_VALUE &&
                (ts == AV_NOPTS_VALUE ||
                 av_compare_ts(ts, sq->streams[stream_idx].tb,
                               st->head_ts, st->tb) < 0)) {
                ts = st->head_ts;
                stream_idx = i;
            }
        }
        /* no stream has a timestamp yet -> nothing to do */
        if (stream_idx < 0)
            return 0;
    }

    st = &sq->streams[stream_idx];

    /* get the chosen stream's tail timestamp */
    for (size_t i = 0; tail_ts == AV_NOPTS_VALUE &&
                       av_container_fifo_peek(st->fifo, (void**)&frame, i) >= 0; i++)
        tail_ts = frame_end(sq, frame, 0);

    /* overflow triggers when the tail is over specified duration behind the head */
    if (tail_ts == AV_NOPTS_VALUE || tail_ts >= st->head_ts ||
        av_rescale_q(st->head_ts - tail_ts, st->tb, AV_TIME_BASE_Q) < sq->buf_size_us)
        return 0;

    /* signal a fake timestamp for all streams that prevent tail_ts from being output */
    tail_ts++;
    for (unsigned int i = 0; i < sq->nb_streams; i++) {
        const SyncQueueStream *st1 = &sq->streams[i];
        int64_t ts;

        if (st == st1 || st1->finished ||
            (st1->head_ts != AV_NOPTS_VALUE &&
             av_compare_ts(tail_ts, st->tb, st1->head_ts, st1->tb) <= 0))
            continue;

        ts = av_rescale_q(tail_ts, st->tb, st1->tb);
        if (st1->head_ts != AV_NOPTS_VALUE)
            ts = FFMAX(st1->head_ts + 1, ts);

        av_log(sq->logctx, AV_LOG_DEBUG, "sq: %u overflow heardbeat %s -> %s\n",
               i, av_ts2timestr(st1->head_ts, &st1->tb), av_ts2timestr(ts, &st1->tb));

        stream_update_ts(sq, i, ts);
    }