一个好的转发模块,首先要低延迟!其次足够稳定灵活、有状态反馈机制、资源占用低,跨平台,最好以接口形式提供,便于第三方系统集成。

以Windows平台为例,我们的考虑的点如下

1. 拉流: 通过RTSP直播播放SDK的数据回调接口,拿到音视频数据;

2. 转推: 通过RTMP直播推送SDK的编码后数据输入接口,把回调上来的数据,传给RTMP直播推送模块,实现RTSP数据流到RTMP服务器的转发;

3. 录像: 如果需要录像,借助RTSP直播播放SDK,拉到音视频数据后,直接存储MP4文件即可;

4. 快照: 如果需要实时快照,拉流后,解码调用播放端快照接口,生成快照,因为快照涉及到video数据解码,如无必要,可不必开启,不然会额外消耗性能。

5. 拉流预览: 如需预览拉流数据,只要调用播放端的播放接口,即可实现拉流数据预览;

6. 数据转AAC后转发: 考虑到好多监控设备出来的音频可能是PCMA/PCMU的,如需要更通用的音频格式,可以转AAC后,在通过RTMP推送;

7. 转推RTMP实时静音: 只需要在传audio数据的地方,加个判断即可;

8. 拉流速度反馈: 通过RTSP播放端的实时码率反馈event,拿到实时带宽占用即可;

9. 整体网络状态反馈: 考虑到有些摄像头可能会临时或异常关闭,RTMP服务器亦是,可以通过推拉流的event回调状态,查看那整体网络情况,如此界定:是拉不到流,还是推不到RTMP服务器。

系统设计架构图

海康推流isupsdk推流到nginx_数据

Windows转发demo分析

大牛直播SDK的转发demo,Windows平台,对应C++ demo工程:WIN-RelaySDK-CPP-Demo,如需下载demo源码,参看 Github

1. 拉流: 拉流和播放有些类似,但不需要播放(也就是说不要解码,资源消耗非常低),在做过基础的参数配置之后(对应demo里面OpenPullHandle()),设置音视频数据回调,然后调用StartPullStream()即可:

1.1 基础参数设置:

bool nt_stream_relay_wrapper::OpenPullHandle(const std::string& url, bool is_rtsp_tcp_mode, bool is_mute)
{
	if ( pull_handle_ != NULL )
		return true;

	if ( url.empty() )
		return false;

	duration_ = 0;

	NT_HANDLE pull_handle = NULL;

	ASSERT( pull_api_ != NULL );
	if (NT_ERC_OK != pull_api_->Open(&pull_handle, render_wnd_, 0, NULL))
	{
		return false;
	}

	ASSERT(pull_handle != NULL);

	pull_api_->SetEventCallBack(pull_handle, this, &NT_Pull_SDKEventHandle);

	pull_api_->SetBuffer(pull_handle, 0);
	pull_api_->SetFastStartup(pull_handle, 1);
	pull_api_->SetRTSPTcpMode(pull_handle, is_rtsp_tcp_mode ? 1 : 0);
	pull_api_->SetMute(pull_handle, is_mute ? 1 : 0);

	if ( NT_ERC_OK != pull_api_->SetURL(pull_handle, url.c_str()) )
	{
		pull_api_->Close(pull_handle);
		pull_handle = NULL;
		return false;
	}

	if ( setting_pos_ >= 0ll )
	{
		pull_api_->SetPos(pull_handle, setting_pos_);
	}

	pull_handle_ = pull_handle;

	return true;
}

1.2 设置音视频数据回调:

pull_api_->SetPullStreamVideoDataCallBack(pull_handle_, this, &SP_SDKPullStreamVideoDataHandle);

	pull_api_->SetPullStreamAudioDataCallBack(pull_handle_, this, &SP_SDKPullStreamAudioDataHandle);

1.3 开始拉流:

auto ret = pull_api_->StartPullStream(pull_handle_);
	if ( NT_ERC_OK != ret )
	{
		if ( !is_playing_ )
		{
			pull_api_->Close(pull_handle_);
			pull_handle_ = NULL;
		}
		
		return false;
	}

拉流整体代码如下:

bool nt_stream_relay_wrapper::StartPull(const std::string& url, bool is_rtsp_tcp_mode, bool is_transcode_aac)
{
	if ( is_pulling_ )
		return false;

	if ( !OpenPullHandle(url, is_rtsp_tcp_mode) )
		return false;

	pull_api_->SetPullStreamVideoDataCallBack(pull_handle_, this, &SP_SDKPullStreamVideoDataHandle);

	pull_api_->SetPullStreamAudioDataCallBack(pull_handle_, this, &SP_SDKPullStreamAudioDataHandle);

	pull_api_->SetPullStreamAudioTranscodeAAC(pull_handle_, is_transcode_aac? 1: 0);

	auto ret = pull_api_->StartPullStream(pull_handle_);
	if ( NT_ERC_OK != ret )
	{
		if ( !is_playing_ )
		{
			pull_api_->Close(pull_handle_);
			pull_handle_ = NULL;
		}
		
		return false;
	}

	is_pulling_ = true;

	return true;
}

2. 停止拉流:

停止拉流流程比较简单,先判断是否在拉流状态,如果拉流,调用StopPullStream() 即可,如没有预览画面,调用Close()接口关闭拉流实例。

void nt_stream_relay_wrapper::StopPull()
{
	if ( !is_pulling_ )
		return;

	pull_api_->StopPullStream(pull_handle_);

	if ( !is_playing_ )
	{
		pull_api_->Close(pull_handle_);
		pull_handle_ = NULL;
	}

	is_pulling_ = false;
}

3. 拉流端预览:

拉流端预览,说白了就是播放拉流数据,流程比较简单,demo调用如下,如不需要播放声音,调用SetMute(),实时打开/关闭即可:

bool nt_stream_relay_wrapper::StartPlay(const std::string& url, bool is_rtsp_tcp_mode, bool is_mute)
{
	if ( is_playing_ )
		return false;

	if ( !OpenPullHandle(url, is_rtsp_tcp_mode, is_mute) )
		return false;

	pull_api_->SetMute(pull_handle_, is_mute ? 1 : 0);

	auto ret = pull_api_->StartPlay(pull_handle_);
	if ( NT_ERC_OK != ret )
	{
		if ( !is_pulling_ )
		{
			pull_api_->Close(pull_handle_);
			pull_handle_ = NULL;
		}

		return false;
	}

	is_playing_ = true;

	return true;
}

4. 拉流端关闭预览:

void nt_stream_relay_wrapper::StopPlay()
{
	if ( !is_playing_ )
		return;

	pull_api_->StopPlay(pull_handle_);

	if ( !is_pulling_ )
	{
		pull_api_->Close(pull_handle_);
		pull_handle_ = NULL;
	}

	is_playing_ = false;
}

5. 开始推流到RTMP服务器:

推流的流程,如之前所述,调用RTMP推送模块,然后数据源传编码后的音视频数据即可,下图的demo源码,同时展示了,RTSP流获取到后,转推RTMP的时候,数据解密的处理:

bool nt_stream_relay_wrapper::StartPush(const std::string& url)
{
	if ( is_pushing_ )
		return false;

	if ( url.empty() )
		return false;

	if ( !OpenPushHandle() )
		return false;

	auto push_handle = GetPushHandle();
	ASSERT(push_handle != nullptr);

	ASSERT(push_api_ != NULL);
	if ( NT_ERC_OK != push_api_->SetURL(push_handle, url.c_str(), NULL) )
	{
		if ( !is_started_rtsp_stream_ )
		{
			push_api_->Close(push_handle);
			SetPushHandle(nullptr);
		}

		return false;
	}

	// 加密测试 +++

	// push_api_->SetRtmpEncryptionOption(push_handle, url.c_str(), 1, 1);

	// NT_BYTE test_key[16] = {'1', '2', '3'};

	// push_api_->SetRtmpEncryptionKey(push_handle, url.c_str(), test_key, 16);

	// 加密测试 --

	if ( NT_ERC_OK != push_api_->StartPublisher(push_handle, NULL) )
	{
		if ( !is_started_rtsp_stream_ )
		{
			push_api_->Close(push_handle);
			SetPushHandle(nullptr);
		}

		return false;
	}


	// // test push rtsp ++

	// push_api_->SetPushRtspTransportProtocol(push_handle, 1);
	// // push_api_->SetPushRtspTransportProtocol(push_handle, 2);

	// push_api_->SetPushRtspURL(push_handle, "rtsp://player.daniulive.com:554/liverelay111.sdp");

	// push_api_->StartPushRtsp(push_handle, 0);

	// // test push rtsp--

	is_pushing_ = true;

	return true;
}

6. 传递转推RTMP数据:

void nt_stream_relay_wrapper::OnVideoDataHandle(NT_HANDLE handle, NT_UINT32 video_codec_id, 
	NT_BYTE* data, NT_UINT32 size, NT_SP_PullStreamVideoDataInfo* info)
{
	if (!is_pushing_ && !is_started_rtsp_stream_)
		return;

	if ( pull_handle_ != handle )
		return;

	if (data == NULL)
		return;

	if (size < 1)
		return;

	if (info == NULL)
		return;

	std::unique_lock<std::recursive_mutex> lock(push_handle_mutex_);

	if (!is_pushing_ && !is_started_rtsp_stream_)
		return;

	if (push_handle_ == NULL)
		return;

	push_api_->PostVideoEncodedDataV2(push_handle_, video_codec_id,
		data, size, info->is_key_frame_, info->timestamp_, info->presentation_timestamp_);
}

void nt_stream_relay_wrapper::OnAudioDataHandle(NT_HANDLE handle, NT_UINT32 auido_codec_id,
	NT_BYTE* data, NT_UINT32 size, NT_SP_PullStreamAuidoDataInfo* info)
{
	if (!is_pushing_ && !is_started_rtsp_stream_)
		return;

	if (pull_handle_ != handle)
		return;

	if (data == NULL)
		return;

	if (size < 1)
		return;

	if (info == NULL)
		return;

	std::unique_lock<std::recursive_mutex> lock(push_handle_mutex_);

	if (!is_pushing_ && !is_started_rtsp_stream_)
		return;

	if (push_handle_ == NULL)
		return;

	push_api_->PostAudioEncodedData(push_handle_, auido_codec_id, data, size,
		info->is_key_frame_, info->timestamp_, 
		info->parameter_info_, info->parameter_info_size_);
}

7. 关闭实时RTMP转推

void nt_stream_relay_wrapper::StopPush()
{
	if ( !is_pushing_ )
		return;

	is_pushing_ = false;

	std::unique_lock<std::recursive_mutex> lock(push_handle_mutex_);

	if ( nullptr == push_handle_ )
		return;

	push_api_->StopPublisher(push_handle_);

	// // test push rtsp ++
	// push_api_->StopPushRtsp(push_handle_);
	// // test push rtsp--


	if ( !is_started_rtsp_stream_ )
	{
		push_api_->Close(push_handle_);

		push_handle_ = nullptr;
	}
}

以上就是RTSP或RTMP流转RTMP推送的流程,感兴趣的开发者,可做设计参考。