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
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。