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。