背景

盡管Windows平臺有諸多優勢，Linux平臺的發展還是勢不可擋，特別實在傳統行業，然而Linux生態構建，總是差點意思，特別是有些常用的組件，本文基于已有的Linux平臺RTSP、RTMP播放模塊，構建Unity下的RTSP和RTMP直播播放。

技術實現

實際上，Unity層面這塊沒什么好介紹的，和Windows、Android、iOS平臺一樣，調用原生的播放模塊，回調解碼后的數據，在Unity繪制，主要的技術難點，還在原生的處理，也就是拉流、解碼、回調數據這塊。

先上個只管感受圖，本視頻以Windows平臺采集秒表計時器窗體，然后編碼打包傳輸到RTMP服務，Unity3D的Linux平臺RTMP播放器拉流播放，整體延遲毫秒級。

Linux平臺，我們是回調的YUV的數據，也就是 NT_SP_E_VIDEO_FRAME_FROMAT_I420：

/*定義視頻幀圖像格式*/public enum NT_SP_E_VIDEO_FRAME_FORMAT : uint{NT_SP_E_VIDEO_FRAME_FORMAT_RGB32 = 1, // 32位的rgb格式, r, g, b各占8, 另外一個字節保留, 內存字節格式為: bb gg rr xx, 主要是和windows位圖匹配, 在小端模式下，按DWORD類型操作，最高位是xx, 依次是rr, gg, bbNT_SP_E_VIDEO_FRAME_FORMAT_ARGB = 2, // 32位的argb格式，內存字節格式是: bb gg rr aa 這種類型，和windows位圖匹配NT_SP_E_VIDEO_FRAME_FROMAT_I420 = 3, // YUV420格式, 三個分量保存在三個面上}

開始播放之前，把回調設置下去：

//video frame callback (YUV/RGB)videoctrl[sel].video_frame_call_back_ = new SP_SDKVideoFrameCallBack(NT_SP_SetVideoFrameCallBack);NTSmartPlayerSDK.NT_SP_SetVideoFrameCallBack(videoctrl[sel].player_handle_, (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FROMAT_I420, window_handle_, videoctrl[sel].video_frame_call_back_);

視頻幀結構：

/*定義視頻幀結構.*/[StructLayoutAttribute(LayoutKind.Sequential)]public struct NT_SP_VideoFrame{public Int32 format_; // 圖像格式, 請參考NT_SP_E_VIDEO_FRAME_FORMATpublic Int32 width_; // 圖像寬public Int32 height_; // 圖像高public Int64 timestamp_; // 時間戳, 一般是0,不使用, 以ms為單位的//具體的圖像數據, argb和rgb32只用第一個, I420用前三個public IntPtr plane0_;public IntPtr plane1_;public IntPtr plane2_;public IntPtr plane3_;// 每一個平面的每一行的字節數，對于argb和rgb32，為了保持和windows位圖兼容，必須是width_*4// 對于I420, stride0_ 是y的步長, stride1_ 是u的步長, stride2_ 是v的步長,public Int32 stride0_;public Int32 stride1_;public Int32 stride2_;public Int32 stride3_;}

具體回調處理：

private void SDKVideoFrameCallBack(UInt32 status, IntPtr frame, int sel){//這里拿到回調frame，進行相關操作NT_SP_VideoFrame video_frame = (NT_SP_VideoFrame)Marshal.PtrToStructure(frame, typeof(NT_SP_VideoFrame));VideoFrame u3d_frame = new VideoFrame();u3d_frame.width_ = video_frame.width_;u3d_frame.height_ = video_frame.height_;u3d_frame.timestamp_ = (UInt64)video_frame.timestamp_;int d_y_stride = video_frame.width_;int d_u_stride = (video_frame.width_ + 1) / 2;int d_v_stride = d_u_stride;int d_y_size = d_y_stride * video_frame.height_;int d_u_size = d_u_stride * ((video_frame.height_ + 1) / 2);int d_v_size = d_u_size;int u_v_height = ((u3d_frame.height_ + 1) / 2);u3d_frame.y_stride_ = d_y_stride;u3d_frame.u_stride_ = d_u_stride;u3d_frame.v_stride_ = d_v_stride;u3d_frame.y_data_ = new byte[d_y_size];u3d_frame.u_data_ = new byte[d_u_size];u3d_frame.v_data_ = new byte[d_v_size];CopyFramePlane(u3d_frame.y_data_, d_y_stride,video_frame.plane0_, video_frame.stride0_, u3d_frame.height_);CopyFramePlane(u3d_frame.u_data_, d_u_stride,video_frame.plane1_, video_frame.stride1_, u_v_height);CopyFramePlane(u3d_frame.v_data_, d_v_stride,video_frame.plane2_, video_frame.stride2_, u_v_height);lock (videoctrl[sel].frame_lock_ ){videoctrl[sel].cur_video_frame_ = u3d_frame;}}

Unity層拿到video frame后，刷新即可：

private void UpdateProc(int sel){VideoFrame video_frame = null;lock (videoctrl[sel].frame_lock_){video_frame = videoctrl[sel].cur_video_frame_;videoctrl[sel].cur_video_frame_ = null;}if ( video_frame == null )return;if (!videoctrl[sel].is_need_get_frame_)return;if (videoctrl[sel].player_handle_ == IntPtr.Zero )return;if ( !videoctrl[sel].is_need_init_texture_){if ( video_frame.width_ != videoctrl[sel].video_width_|| video_frame.height_ != videoctrl[sel].video_height_|| video_frame.y_stride_ != videoctrl[sel].y_row_bytes_|| video_frame.u_stride_ != videoctrl[sel].u_row_bytes_|| video_frame.v_stride_ != videoctrl[sel].v_row_bytes_ ){videoctrl[sel].is_need_init_texture_ = true;}}if (videoctrl[sel].is_need_init_texture_){if (InitYUVTexture(video_frame, sel)){videoctrl[sel].is_need_init_texture_ = false;}}UpdateYUVTexture(video_frame, sel);}

UpdateYUVTexture相關實現：

private void UpdateYUVTexture(VideoFrame video_frame, int sel){if (video_frame.y_data_ == null || video_frame.u_data_ == null || video_frame.v_data_ == null){Debug.Log("video frame with null..");return;}if (videoctrl[sel].yTexture_ != null){videoctrl[sel].yTexture_.LoadRawTextureData(video_frame.y_data_);videoctrl[sel].yTexture_.Apply();}if (videoctrl[sel].uTexture_ != null){videoctrl[sel].uTexture_.LoadRawTextureData(video_frame.u_data_);videoctrl[sel].uTexture_.Apply();}if (videoctrl[sel].vTexture_ != null){videoctrl[sel].vTexture_.LoadRawTextureData(video_frame.v_data_);videoctrl[sel].vTexture_.Apply();}}

相關Player封裝：

/** SmartPlayerLinuxMono.cs** WebSite: https://daniusdk.com* Github: https://github.com/daniulive/SmarterStreaming*/public void Play(int sel){if (videoctrl[sel].is_running){Debug.Log("已經在播放..");return;}lock (videoctrl[sel].frame_lock_){videoctrl[sel].cur_video_frame_ = null;}OpenPlayer(sel);if (videoctrl[sel].player_handle_ == IntPtr.Zero)return;//設置播放URLNTSmartPlayerSDK.NT_SP_SetURL(videoctrl[sel].player_handle_, videoctrl[sel].videoUrl);/* ++ 播放前參數配置可加在此處 ++ */int play_buffer_time_ = 0;NTSmartPlayerSDK.NT_SP_SetBuffer(videoctrl[sel].player_handle_, play_buffer_time_); //設置buffer timeint is_using_tcp = 0; //TCP模式NTSmartPlayerSDK.NT_SP_SetRTSPTcpMode(videoctrl[sel].player_handle_, is_using_tcp);int timeout = 10;NTSmartPlayerSDK.NT_SP_SetRtspTimeout(videoctrl[sel].player_handle_, timeout);int is_auto_switch_tcp_udp = 1;NTSmartPlayerSDK.NT_SP_SetRtspAutoSwitchTcpUdp(videoctrl[sel].player_handle_, is_auto_switch_tcp_udp);Boolean is_mute_ = false;NTSmartPlayerSDK.NT_SP_SetMute(videoctrl[sel].player_handle_, is_mute_ ? 1 : 0); //是否啟動播放的時候靜音int is_fast_startup = 1;NTSmartPlayerSDK.NT_SP_SetFastStartup(videoctrl[sel].player_handle_, is_fast_startup); //設置快速啟動模式Boolean is_low_latency_ = false;NTSmartPlayerSDK.NT_SP_SetLowLatencyMode(videoctrl[sel].player_handle_, is_low_latency_ ? 1 : 0); //設置是否啟用低延遲模式//設置旋轉角度(設置0， 90， 180， 270度有效，其他值無效)int rotate_degrees = 0;NTSmartPlayerSDK.NT_SP_SetRotation(videoctrl[sel].player_handle_, rotate_degrees);int volume = 100;NTSmartPlayerSDK.NT_SP_SetAudioVolume(videoctrl[sel].player_handle_, volume); //設置播放音量, 范圍是[0, 100], 0是靜音，100是最大音量, 默認是100// 設置上傳下載報速度int is_report = 0;int report_interval = 1;NTSmartPlayerSDK.NT_SP_SetReportDownloadSpeed(videoctrl[sel].player_handle_, is_report, report_interval);/* -- 播放前參數配置可加在此處 -- *///video frame callback (YUV/RGB)videoctrl[sel].video_frame_call_back_ = new SP_SDKVideoFrameCallBack(NT_SP_SetVideoFrameCallBack);NTSmartPlayerSDK.NT_SP_SetVideoFrameCallBack(videoctrl[sel].player_handle_, (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FROMAT_I420, window_handle_, videoctrl[sel].video_frame_call_back_);UInt32 flag = NTSmartPlayerSDK.NT_SP_StartPlay(videoctrl[sel].player_handle_);if (flag == DANIULIVE_RETURN_OK){videoctrl[sel].is_need_get_frame_ = true;Debug.Log("播放成功");}else{videoctrl[sel].is_need_get_frame_ = false;Debug.LogError("播放失敗");}videoctrl[sel].is_running = true;}

調用到的OpenPlayer實現：

OpenPlayer主要是調用底層NT_SP_Open()接口，獲取播放實例句柄，然后設置Event回調等。

private void OpenPlayer(int sel){window_handle_ = IntPtr.Zero;if (videoctrl[sel].player_handle_ == IntPtr.Zero){videoctrl[sel].player_handle_ = new IntPtr();UInt32 ret_open = NTSmartPlayerSDK.NT_SP_Open(out videoctrl[sel].player_handle_, window_handle_, 0, IntPtr.Zero);if (ret_open != 0){videoctrl[sel].player_handle_ = IntPtr.Zero;Debug.LogError("調用NT_SP_Open失敗..");return;}}videoctrl[sel].event_call_back_ = new SP_SDKEventCallBack(NT_SP_SDKEventCallBack);NTSmartPlayerSDK.NT_SP_SetEventCallBack(videoctrl[sel].player_handle_, window_handle_, videoctrl[sel].event_call_back_);videoctrl[sel].sdk_video_frame_call_back_ = new VideoControl.SetVideoFrameCallBack(SDKVideoFrameCallBack);videoctrl[sel].sdk_event_call_back_ = new VideoControl.SetEventCallBack(SDKEventCallBack);}

關閉播放：

private void ClosePlayer(int sel){videoctrl[sel].is_need_get_frame_ = false;videoctrl[sel].is_need_init_texture_ = false;if (videoctrl[sel].player_handle_ == IntPtr.Zero){return;}UInt32 flag = NTSmartPlayerSDK.NT_SP_StopPlay(videoctrl[sel].player_handle_);if (flag == DANIULIVE_RETURN_OK){Debug.Log("停止成功");}else{Debug.LogError("停止失敗");}videoctrl[sel].player_handle_ = IntPtr.Zero;videoctrl[sel].is_running = false;}

總結

Unity環境下的直播播放，Windows平臺或者Android的比較多，用在Linux平臺的少之又少，一方面Linux平臺本身需求不大，另一方面，Linux平臺這塊，可參考的例程不多，實際上，如果已經完成Windows或Android平臺下的核心功能實現，再移植到Linux下，非常方便。

Unity下，簡單來說就是拉流解碼回調，上層繪制，其實也沒有那么復雜，需要注意的是DllImport的寫法、之前C++結構體或枚舉的轉換、Unity3D對Linux的版本兼容等一些細節，對熟悉C#的開發者來說，不具備多大的技術難度。

總結

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