rtp_parse_one_packet_rtpparse-优快云博客

本文深入探讨了RTP协议中一个包的解析过程，包括如何处理RTCP包，如何更新jitter统计，以及如何处理包序列和重排序。通过详细的代码分析，展示了RTP包解析的内部机制。

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static int rtp_parse_one_packet(RTPDemuxContext *s, AVPacket *pkt,
                                uint8_t **bufptr, int len)
{
    uint8_t *buf = bufptr ? *bufptr : NULL;
    int flags = 0;
    uint32_t timestamp;
    int rv = 0;

    if (!buf) {
        /* If parsing of the previous packet actually returned 0 or an error,
         * there's nothing more to be parsed from that packet, but we may have
         * indicated that we can return the next enqueued packet. */
        if (s->prev_ret <= 0)
            return rtp_parse_queued_packet(s, pkt);
        /* return the next packets, if any */
        if (s->handler && s->handler->parse_packet) {
            /* timestamp should be overwritten by parse_packet, if not,
             * the packet is left with pts == AV_NOPTS_VALUE */
            timestamp = RTP_NOTS_VALUE;
            rv        = s->handler->parse_packet(s->ic, s->dynamic_protocol_context,
                                                 s->st, pkt, &timestamp, NULL, 0, 0,
                                                 flags);
            finalize_packet(s, pkt, timestamp);
            return rv;
        }
    }

    if (len < 12)
        return -1;

    if ((buf[0] & 0xc0) != (RTP_VERSION << 6))
        return -1;
    if (RTP_PT_IS_RTCP(buf[1])) {
		av_log(NULL, AV_LOG_ERROR, "%s:%d============!!!\n",__func__,__LINE__);//
        return rtcp_parse_packet(s, buf, len);
    }

    if (s->st) {
		av_log(NULL, AV_LOG_ERROR, "%s:%d============!!!\n",__func__,__LINE__);//
        int64_t received = av_gettime_relative();
        uint32_t arrival_ts = av_rescale_q(received, AV_TIME_BASE_Q,
                                           s->st->time_base);
        timestamp = AV_RB32(buf + 4);
        // Calculate the jitter immediately, before queueing the packet
        // into the reordering queue.
        rtcp_update_jitter(&s->statistics, timestamp, arrival_ts);
    }

    if ((s->seq == 0 && !s->queue) || s->queue_size <= 1) {
		av_log(NULL, AV_LOG_ERROR, "%s:%d============!!!\n",__func__,__LINE__);//
        /* First packet, or no reordering */
        return rtp_parse_packet_internal(s, pkt, buf, len);
    } else {
		av_log(NULL, AV_LOG_ERROR, "%s:%d============!!!\n",__func__,__LINE__);//
        uint16_t seq = AV_RB16(buf + 2);
        int16_t diff = seq - s->seq;
        if (diff < 0) {
            /* Packet older than the previously emitted one, drop */
            av_log(s->ic, AV_LOG_WARNING,
                   "RTP: dropping old packet received too late\n");
            return -1;
        } else if (diff <= 1) {
			av_log(NULL, AV_LOG_ERROR, "%s:%d============!!!\n",__func__,__LINE__);//
            /* Correct packet */
            rv = rtp_parse_packet_internal(s, pkt, buf, len);
            return rv;
        } else {
            /* Still missing some packet, enqueue this one. */
            rv = enqueue_packet(s, buf, len);
            if (rv < 0)
                return rv;
            *bufptr = NULL;
            /* Return the first enqueued packet if the queue is full,
             * even if we're missing something */
            if (s->queue_len >= s->queue_size) {
                av_log(s->ic, AV_LOG_WARNING, "jitter buffer full\n");
                return rtp_parse_queued_packet(s, pkt);
            }
            return -1;
        }
    }
}