ffmpeg是怎么处理rtp时间戳(pts)

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• 在文件rtpdec.c里
• 分两种情况：1、有ntp时间（就是有sr包）；2、没有ntp时间

/**
 * This was the second switch in rtp_parse packet.
 * Normalizes time, if required, sets stream_index, etc.
 */
static void finalize_packet(RTPDemuxContext *s, AVPacket *pkt, uint32_t timestamp)
{
    if (pkt->pts != AV_NOPTS_VALUE || pkt->dts != AV_NOPTS_VALUE)
        return; /* Timestamp already set by depacketizer */
    if (timestamp == RTP_NOTS_VALUE)
        return;

    if (s->last_rtcp_ntp_time != AV_NOPTS_VALUE && s->ic->nb_streams > 1) {
        int64_t addend;
        int delta_timestamp;

        /* compute pts from timestamp with received ntp_time */
        delta_timestamp = timestamp - s->last_rtcp_timestamp;
        /* convert to the PTS timebase */
        addend = av_rescale(s->last_rtcp_ntp_time - s->first_rtcp_ntp_time,
                            s->st->time_base.den,
                            (uint64_t) s->st->time_base.num << 32);
        pkt->pts = s->range_start_offset + s->rtcp_ts_offset + addend +
                   delta_timestamp;
        return;
    }

    if (!s->base_timestamp)
        s->base_timestamp = timestamp;
    /* assume that the difference is INT32_MIN < x < INT32_MAX,
     * but allow the first timestamp to exceed INT32_MAX */
    if (!s->timestamp)
        s->unwrapped_timestamp += timestamp;
    else
        s->unwrapped_timestamp += (int32_t)(timestamp - s->timestamp);
    s->timestamp = timestamp;
    pkt->pts     = s->unwrapped_timestamp + s->range_start_offset -
                   s->base_timestamp;
}

参考：https://www.jianshu.com/p/67d3e6a1d72e