metartc5_jz源码阅读-yang_rtcpush_on_rtcp_nack

//发送端收到接收端发来的rtcp nack命令，需要丢包重传
int32_t yang_rtcpush_on_rtcp_nack(YangRtcContext *context,
		YangRtcPushStream *pub, YangRtcpCommon *rtcp) {
	//容错处理
	if (context == NULL || pub == NULL||rtcp==NULL)
		return ERROR_RTC_PUBLISH;
	int32_t err = Yang_Ok;

	//根据rtcp->nack->mediaSsrc判断是音频包丢失还是视频包丢失，拿到保存发送音视频包的queue
	YangPublishNackBuffer *que = NULL;
    uint32_t ssrc = rtcp->nack->mediaSsrc;
	if (ssrc == pub->audioSsrc)		que = pub->audio_queue;
	if (ssrc == pub->videoSsrc)		que = pub->video_queue;

	if (!ssrc)	return yang_error_wrap(err, "track response nack  ssrc=%u", ssrc);

	//将存放发送音视频包的quque传入yang_rtcpush_on_recv_nack中。
	if (que && (err = yang_rtcpush_on_recv_nack(context, pub, que,rtcp->nack)) != Yang_Ok) {
		return yang_error_wrap(err, "track response nack.  ssrc=%u", ssrc);
	}
	return err;
}

//从发送音视频包的队列中取出对应的包进行发送。
int32_t yang_rtcpush_on_recv_nack(YangRtcContext *context,
		YangRtcPushStream *pub, YangPublishNackBuffer *que,
		YangRtcpNack *nack) {
	if (context == NULL || pub == NULL)
		return ERROR_RTC_PUBLISH;
	int32_t err = Yang_Ok;

	//遍历nack->nacks数组
	for (int32_t i = 0; i < nack->vsize; ++i) {

		//拿到丢包对应的sequence
		uint16_t seq = nack->nacks[i];

		//根据sequence从que队列中取出对应的rtp包。
		YangSendNackBuffer *pkt = yang_rtcpush_fetch_rtp_packet(context, pub,
				que, seq);
		if (pkt == NULL) {
			continue;
		}
		yang_trace("\nsendlostsn=%hu,", seq);

		//nackCount统计加一
		context->stats.sendStats.nackCount++;

		//调用yang_send_nackpacket方法发送rtp包的payload.
		if ((err = yang_send_nackpacket(context, pkt->payload, pkt->nb))!= Yang_Ok) {
			return yang_error_wrap(err, "raw send");
		}
	}

	return err;
}