我們在實現Windows平臺RTSP播放器或RTMP播放器的時候，需要考慮的點很多，比如多實例設計、多繪制模式兼容、軟硬解碼支持、快照、RTSP下TCP-UDP自動切換等，以下就其中幾個方面，做個大概的探討。

1. 視頻繪制模式

我們在實現Windows平臺播放的時候，一般首選D3D，D3D不支持的情況下，考慮數據回上來，采用GDI模式，一般實現如下，先做D3D檢測，以大牛直播SDK播放端為例（Github），調用NT_SP_IsSupportD3DRender()，檢測是否支持D3D模式，如果支持的話，調用NT_SP_SetRenderWindow(), 然后，設置是否等比例縮放（調用NT_SP_SetRenderScaleMode()）。

bool is_support_d3d_render = false;Int32 in_support_d3d_render = 0;if (NT.NTBaseCodeDefine.NT_ERC_OK == NTSmartPlayerSDK.NT_SP_IsSupportD3DRender(player_handle_, playWnd.Handle, ref in_support_d3d_render)){if (1 == in_support_d3d_render){is_support_d3d_render = true;}}if (is_support_d3d_render){is_gdi_render_ = false;// 支持d3d繪制的話，就用D3D繪制NTSmartPlayerSDK.NT_SP_SetRenderWindow(player_handle_, playWnd.Handle);if (btn_check_render_scale_mode.Checked){NTSmartPlayerSDK.NT_SP_SetRenderScaleMode(player_handle_, 1);}else{NTSmartPlayerSDK.NT_SP_SetRenderScaleMode(player_handle_, 0);}}else{is_gdi_render_ = true;playWnd.Visible = false;// 不支持D3D就讓播放器吐出數據來，用GDI繪制//video frame callback (YUV/RGB)//format請參見 NT_SP_E_VIDEO_FRAME_FORMAT，如需回調YUV，請設置為 NT_SP_E_VIDEO_FRAME_FROMAT_I420video_frame_call_back_ = new SP_SDKVideoFrameCallBack(SetVideoFrameCallBack);NTSmartPlayerSDK.NT_SP_SetVideoFrameCallBack(player_handle_, (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FORMAT_RGB32, IntPtr.Zero, video_frame_call_back_);}

如果不支持D3D，設置RGB數據回調：

video_frame_call_back_ = new SP_SDKVideoFrameCallBack(SetVideoFrameCallBack);NTSmartPlayerSDK.NT_SP_SetVideoFrameCallBack(player_handle_, (Int32)NT.NTSmartPlayerDefine.NT_SP_E_VIDEO_FRAME_FORMAT.NT_SP_E_VIDEO_FRAME_FORMAT_RGB32, IntPtr.Zero, video_frame_call_back_);

數據處理如下：

public void SetVideoFrameCallBack(IntPtr handle, IntPtr userData, UInt32 status, IntPtr frame){if (frame == IntPtr.Zero){return;}//如需直接處理RGB數據，請參考以下流程NT_SP_VideoFrame video_frame = (NT_SP_VideoFrame)Marshal.PtrToStructure(frame, typeof(NT_SP_VideoFrame));NT_SP_VideoFrame pVideoFrame = new NT_SP_VideoFrame();pVideoFrame.format_ = video_frame.format_;pVideoFrame.width_ = video_frame.width_;pVideoFrame.height_ = video_frame.height_;pVideoFrame.timestamp_ = video_frame.timestamp_;pVideoFrame.stride0_ = video_frame.stride0_;pVideoFrame.stride1_ = video_frame.stride1_;pVideoFrame.stride2_ = video_frame.stride2_;pVideoFrame.stride3_ = video_frame.stride3_;Int32 argb_size = video_frame.stride0_ * video_frame.height_;pVideoFrame.plane0_ = Marshal.AllocHGlobal(argb_size);CopyMemory(pVideoFrame.plane0_, video_frame.plane0_, (UInt32)argb_size);if (playWnd.InvokeRequired){BeginInvoke(set_video_frame_call_back_, status, pVideoFrame);}else{set_video_frame_call_back_(status, pVideoFrame);}}

在OnPaint()繪制即可：

private void SmartPlayerForm_Paint(object sender, PaintEventArgs e){if (player_handle_ == IntPtr.Zero || !is_gdi_render_ || !is_playing_){return;}if (cur_video_frame_.plane0_ == IntPtr.Zero){return;}Bitmap bitmap = new Bitmap(cur_video_frame_.width_, cur_video_frame_.height_, cur_video_frame_.stride0_,System.Drawing.Imaging.PixelFormat.Format32bppRgb, cur_video_frame_.plane0_);int image_width = cur_video_frame_.width_;int image_height = cur_video_frame_.height_;Graphics g = e.Graphics; //獲取窗體畫布g.SmoothingMode = SmoothingMode.HighSpeed;int limit_w = this.Width - 60;int limit_h = this.Height - playWnd.Top - 60;if (btn_check_render_scale_mode.Checked){int d_w = 0, d_h = 0;int left_offset = 0;int top_offset = 0;Brush brush = new SolidBrush(Color.Black);g.FillRectangle(brush, playWnd.Left, playWnd.Top, limit_w, limit_h);GetRenderRect(limit_w, limit_h, image_width, image_height, ref left_offset, ref top_offset, ref d_w, ref d_h);g.DrawImage(bitmap, playWnd.Left + left_offset, playWnd.Top + top_offset, d_w, d_h); //在窗體的畫布中繪畫出內存中的圖像}else{g.DrawImage(bitmap, playWnd.Left, playWnd.Top, limit_w, limit_h); //在窗體的畫布中繪畫出內存中的圖像}}

2. 特定機型硬解碼

Windows平臺硬解碼，主要適用于性能偏弱的PC端，或者有多路播放訴求的場景，一般建議在軟解性能沒問題的情況下，盡量軟解，具體處理如下，先檢測系統是否支持硬解，如果支持，再做硬解設置，這樣的好處在于如果系統不支持硬解，可以繼續軟解播放，具體設置如下，在調用NT_SP_Open()之前，做檢測，因為NT_SP_Open()每個句柄對應一個player實例，多個實例只需要做一次判斷即可：

is_support_h264_hardware_decoder_ = NT.NTBaseCodeDefine.NT_ERC_OK == NT.NTSmartPlayerSDK.NT_SP_IsSupportH264HardwareDecoder();is_support_h265_hardware_decoder_ = NT.NTBaseCodeDefine.NT_ERC_OK == NT.NTSmartPlayerSDK.NT_SP_IsSupportH265HardwareDecoder();if (player_handle_ == IntPtr.Zero){player_handle_ = new IntPtr();UInt32 ret_open = NTSmartPlayerSDK.NT_SP_Open(out player_handle_, IntPtr.Zero, 0, IntPtr.Zero);if (ret_open != 0){player_handle_ = IntPtr.Zero;MessageBox.Show("調用NT_SP_Open失敗..");return;}}

播放之前，設置硬解碼：

if (checkBox_hardware_decoder.Checked){NTSmartPlayerSDK.NT_SP_SetH264HardwareDecoder(player_handle_, is_support_h264_hardware_decoder_ ? 1 : 0, 0);NTSmartPlayerSDK.NT_SP_SetH265HardwareDecoder(player_handle_, is_support_h265_hardware_decoder_ ? 1 : 0, 0);}else{NTSmartPlayerSDK.NT_SP_SetH264HardwareDecoder(player_handle_, 0, 0);NTSmartPlayerSDK.NT_SP_SetH265HardwareDecoder(player_handle_, 0, 0);}

3. 只解碼關鍵幀

只解關鍵幀的場景，也是用于多路播放訴求，比如一般的監控場景，考慮到多路的場景，一般關鍵幀間隔不大（如1-2秒一個），平臺可對現場場景有個宏觀了解，如需重點關注某幾路畫面的時候，再實時取消這個選項，實現全幀播放，所以，只解關鍵幀一定要做成實時調用的接口才更有設計意義。

// 設置是否只解碼關鍵幀if (btn_check_only_decode_video_key_frame.Checked){NTSmartPlayerSDK.NT_SP_SetOnlyDecodeVideoKeyFrame(player_handle_, 1);}else{NTSmartPlayerSDK.NT_SP_SetOnlyDecodeVideoKeyFrame(player_handle_, 0);}

4. 視頻view旋轉

好多現場的開發人員有這樣的困惑，有些設備，在安裝時，可能沒調整好角度，導致拍出來的角度倒立等，看著很不方便，這時候，如果現場設備比較多的話，不可能每臺設備都到現場重新安裝，實時view旋轉，就體現了價值，具體如下：

/** 設置旋轉，順時針旋轉* degress： 設置0， 90， 180， 270度有效，其他值無效* 注意：除了0度，其他角度播放會耗費更多CPU* 接口調用成功返回NT_ERC_OK*/[DllImport(@"SmartPlayerSDK.dll")]public static extern UInt32 NT_SP_SetRotation(IntPtr handle, Int32 degress);

視頻view選擇，會消耗一定的CPU。

5. 實時快照

實時快照功能不表，是一個好的RTSP播放器和RTMP播放器必備的功能，實時快照是把解碼后的yuv數據重新編碼成png，所以有一定的CPU消耗，不建議過于頻繁操作，具體實現如下：

if ( String.IsNullOrEmpty(capture_image_path_) ){MessageBox.Show("請先設置保存截圖文件的目錄! 點擊截圖左邊的按鈕設置!");return;}if ( player_handle_ == IntPtr.Zero ){return;}if ( !is_playing_){MessageBox.Show("請在播放狀態下截圖!");return;}String name = capture_image_path_ + "\\" + DateTime.Now.ToString("hh-mm-ss") + ".png";byte[] buffer1 = Encoding.Default.GetBytes(name);byte[] buffer2 = Encoding.Convert(Encoding.Default, Encoding.UTF8, buffer1, 0, buffer1.Length);byte[] buffer3 = new byte[buffer2.Length + 1];buffer3[buffer2.Length] = 0;Array.Copy(buffer2, buffer3, buffer2.Length);IntPtr file_name_ptr = Marshal.AllocHGlobal(buffer3.Length);Marshal.Copy(buffer3, 0, file_name_ptr, buffer3.Length);capture_image_call_back_ = new SP_SDKCaptureImageCallBack(SDKCaptureImageCallBack);UInt32 ret = NTSmartPlayerSDK.NT_SP_CaptureImage(player_handle_, file_name_ptr, IntPtr.Zero, capture_image_call_back_);Marshal.FreeHGlobal(file_name_ptr);if (NT.NTBaseCodeDefine.NT_ERC_OK == ret){// 發送截圖請求成功}else if ((UInt32)NT.NTSmartPlayerDefine.SP_E_ERROR_CODE.NT_ERC_SP_TOO_MANY_CAPTURE_IMAGE_REQUESTS == ret){// 通知用戶延時MessageBox.Show("Too many capture image requests!");}else{// 其他失敗} public void SDKCaptureImageCallBack(IntPtr handle, IntPtr userData, UInt32 result, IntPtr file_name){if (file_name == IntPtr.Zero)return;int index = 0;while (true){if (0 == Marshal.ReadByte(file_name, index))break;index++;}byte[] file_name_buffer = new byte[index];Marshal.Copy(file_name, file_name_buffer, 0, index);byte[] dst_buffer = Encoding.Convert(Encoding.UTF8, Encoding.Default, file_name_buffer, 0, file_name_buffer.Length);String image_name = Encoding.Default.GetString(dst_buffer, 0, dst_buffer.Length);if (playWnd.InvokeRequired){BeginInvoke(set_capture_image_call_back_, result, image_name);}else{set_capture_image_call_back_(result, image_name);}}

后續，我們將針對RTSP和RTMP播放器設計過程中的其他點，做更進一步的探討。

總結

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