Windows平台RTSP播放器/RTMP播放器设计需要考虑的几个点

我们在实现Windows平台RTSP播放器或RTMP播放器的时候，需要考虑的点很多，比如多实例设计、多绘制模式兼容、软硬解码支持、快照、RTSP下TCP-UDP自动切换等，以下就其中几个方面，做个大概的探讨。

1. 视频绘制模式

我们在实现Windows平台播放的时候，一般首选D3D，D3D不支持的情况下，考虑数据回上来，采用GDI模式，一般实现如下，先做D3D检测，以大牛直播SDK播放端为例（Github），调用NT_SP_IsSupportD3DRender()，检测是否支持D3D模式，如果支持的话，调用NT_SP_SetRenderWindow(), 然后，设置是否等比例缩放（调用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绘制的话，就用D3D绘制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就让播放器吐出数据来，用GDI绘制//video frame callback (YUV/RGB)//format请参见 NT_SP_E_VIDEO_FRAME_FORMAT，如需回调YUV，请设置为 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，设置RGB数据回调：

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_);

数据处理如下：

        public void SetVideoFrameCallBack(IntPtr handle, IntPtr userData, UInt32 status, IntPtr frame){if (frame == IntPtr.Zero){return;}//如需直接处理RGB数据，请参考以下流程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()绘制即可：

        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;    //获取窗体画布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);   //在窗体的画布中绘画出内存中的图像}else{g.DrawImage(bitmap, playWnd.Left, playWnd.Top, limit_w, limit_h);   //在窗体的画布中绘画出内存中的图像}}

2. 特定机型硬解码

Windows平台硬解码，主要适用于性能偏弱的PC端，或者有多路播放诉求的场景，一般建议在软解性能没问题的情况下，尽量软解，具体处理如下，先检测系统是否支持硬解，如果支持，再做硬解设置，这样的好处在于如果系统不支持硬解，可以继续软解播放，具体设置如下，在调用NT_SP_Open()之前，做检测，因为NT_SP_Open()每个句柄对应一个player实例，多个实例只需要做一次判断即可：

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("调用NT_SP_Open失败..");return;}}

播放之前，设置硬解码：

            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. 只解码关键帧

只解关键帧的场景，也是用于多路播放诉求，比如一般的监控场景，考虑到多路的场景，一般关键帧间隔不大（如1-2秒一个），平台可对现场场景有个宏观了解，如需重点关注某几路画面的时候，再实时取消这个选项，实现全帧播放，所以，只解关键帧一定要做成实时调用的接口才更有设计意义。

            // 设置是否只解码关键帧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. 视频view旋转

好多现场的开发人员有这样的困惑，有些设备，在安装时，可能没调整好角度，导致拍出来的角度倒立等，看着很不方便，这时候，如果现场设备比较多的话，不可能每台设备都到现场重新安装，实时view旋转，就体现了价值，具体如下：

     /** 设置旋转，顺时针旋转* degress： 设置0， 90， 180， 270度有效，其他值无效* 注意：除了0度，其他角度播放会耗费更多CPU* 接口调用成功返回NT_ERC_OK*/[DllImport(@"SmartPlayerSDK.dll")]public static extern UInt32 NT_SP_SetRotation(IntPtr handle, Int32 degress);

视频view选择，会消耗一定的CPU。

5. 实时快照

实时快照功能不表，是一个好的RTSP播放器和RTMP播放器必备的功能，实时快照是把解码后的yuv数据重新编码成png，所以有一定的CPU消耗，不建议过于频繁操作，具体实现如下：

            if ( String.IsNullOrEmpty(capture_image_path_) ){MessageBox.Show("请先设置保存截图文件的目录! 点击截图左边的按钮设置!");return;}if ( player_handle_ == IntPtr.Zero ){return;}if ( !is_playing_){MessageBox.Show("请在播放状态下截图!");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){// 发送截图请求成功}else if ((UInt32)NT.NTSmartPlayerDefine.SP_E_ERROR_CODE.NT_ERC_SP_TOO_MANY_CAPTURE_IMAGE_REQUESTS == ret){// 通知用户延时MessageBox.Show("Too many capture image requests!");}else{// 其他失败}

        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);}}

后续，我们将针对RTSP和RTMP播放器设计过程中的其他点，做更进一步的探讨。