SRS中RTMP推流RTC播放的实现原理及函数执行流程

RTMP转RTC；或者RTC转RTMP，是通过Bridger实现的。

RTMP转RTC

class SrsRtcFromRtmpBridger : public ISrsLiveSourceBridger

RTMP推流

HTTP回调,类似RTMP module中onpublish回调

创建接收推流的Thread

publishing

http_hooks_on_publish

acquire_publish

do_publishing

创建RtcFromRtmpBridger

在acquire_publish函数中：

    if (rtc_server_enabled && rtc_enabled && !info->edge) {
        if ((err = _srs_rtc_sources->fetch_or_create(req, &rtc)) != srs_success) {
            return srs_error_wrap(err, "create source");
        }

        if (!rtc->can_publish()) {
            return srs_error_new(ERROR_RTC_SOURCE_BUSY, "rtc stream %s busy", req->get_stream_url().c_str());
        }
    }

判断配置文件中是否配置并开启了RTC服务，还需要当前服务不是Edge类型节点的服务。如果条件都满足，会根据RTMP推流的req信息（application和streamname）获取或创建SrsRtcSource对象rtc。

if (rtc) {
        SrsRtcFromRtmpBridger *bridger = new SrsRtcFromRtmpBridger(rtc);
        if ((err = bridger->initialize(req)) != srs_success) {
            srs_freep(bridger);
            return srs_error_wrap(err, "bridger init");
        }

        source->set_bridger(bridger);
    }

创建SrsRtcFromRtmpBridger的桥接对象bridger，使用RTMP推流的req信息初始化bridger，其中包括初始化音频转码，从AAC转Opus。最后将bridger设置进SrsLiveSource* source中，供后续接收到音视频数据时使用。

RTMP接收推流线程

        SrsPublishRecvThread rtrd(rtmp, req, srs_netfd_fileno(stfd), 0, this, source, _srs_context->get_id());
        err = do_publishing(source, &rtrd);

创建接收RTMP推流的线程并启动。
线程创建的过程：

graph TD
SrsPublishRecvThread--构造函数初始化trd-->B[SrsRecvThread trd]
B --创建SrsDummyCoroutine-->C[SrsDummyCoroutine trd]

线程启动

启动隔离接收线程

创建ST协程

实际是创建

_pfn_st_thread_create

开启循环执行SrsFastCoroutine::cycle

即执行传入的接收函数

pumper = SrsPublishRecvThread

存在bridger_

AAC to Opus

for循环 封装SrsRtpPacket

存在bridger_

封装SrsRtpPacket

RTC拉流方SrsRtcConsumer

添加进待发送的SrsRtpPacket队列

SrsRtcPlayStream::cycle

do_publishing

SrsPublishRecvThread rtrd->start

SrsRecvThread trd.start

trd = new SrsSTCoroutine

SrsFastCoroutine

SrsSTCoroutine trd->start

SrsFastCoroutine::start

st_thread_create

SrsFastCoroutine::cycle

SrsRecvThread::cycle

do_cycle

rtmp->recv_message

pumper->consume msg

SrsPublishRecvThread::consume

handle_publish_message

process_publish_message

source->on_audio, on_audio_imp

source->on_video, on_video_imp

bridger_->on_audio

transcode

SrsRtcSource source_->on_rtp

bridger_->on_video

SrsRtcFromRtmpBridger consume_packets

consumer->enqueue

queue.push_back pkt

consumerdump_packet获取队列数据后send_packet

RTC转RTMP

class SrsRtmpFromRtcBridger : public ISrsRtcSourceBridger