分类： C/C++
2008-08-21 11:51:15
点对点视频会议程序:VideoNet
作者：
翻译：POWERCPP
该程序可以用于两个人在LAN/Intranet(或者Internet)上进行视频会议。现在有许多视频会议程序，每个都有各自的性能提升技术。主要的问题是视频会议视频帧的尺寸对于传输来说太大。因此，性能依赖于对帧的编解码。我使用快速h263编码库来达到更好的压缩率提高速度。该程序做些小改动也可以在Internet上使用。
音频的录制与播放
我在以前的语音会议程序中使用了RecordSound和PlaySound类，这里我将提供摘要说明RecordSound和PlaySound类的使用。
// Create and Start Recorder Thread record=new RecordSound(this); record->CreateThread(); // Create and Start Player Thread play=new PlaySound1(this); play->CreateThread(); // Start Recording record->PostThreadMessage(WM_RECORDSOUND_STARTRECORDING,0,0); // Start Playing play->PostThreadMessage(WM_PLAYSOUND_STARTPLAYING,0,0); // During audio recording, data will be available in the OnSoundData // callback function of the RecordSound class. Here, you can place // your code to send the data to remote host... // To play the data received from the remote host play->PostThreadMessage(WM_PLAYSOUND_PLAYBLOCK,size,(LPARAM)data); // Stop Recording record->PostThreadMessage(WM_RECORDSOUND_STOPRECORDING,0,0); // Stop Playing play->PostThreadMessage(WM_PLAYSOUND_STOPPLAYING,0,0); // At last, to Stop the Recording Thread record->PostThreadMessage(WM_RECORDSOUND_ENDTHREAD,0,0); // To stop playing thread... play->PostThreadMessage(WM_PLAYSOUND_ENDTHREAD,0,0);
视频捕获
使用VFW(Video For Windows)API进行视频捕获，它提供了通过webcam进行视频捕获。 VideoCapture.h 和VideoCapture.cpp包含了处理视频捕获的代码。
如下代码说明了如何使用该类：
// Create instance of Class vidcap=new VideoCapture(); // This is later used to call display function of the main // dialog class when the frame is captured... vidcap->SetDialog(this); // This does lot of work, including connecting to the driver // and setting the desired video format. Returns TRUE if // successfully connected to videocapture device. vidcap->Initialize(); // If successfully connected, you can get the BITMAPINFO // structure associated with the video format. This is later // used to display the captured frame... this->m_bmpinfo=&vidcap->m_bmpinfo; // Now you can start the capture.... vidcap->StartCapture(); // Once capture is started, frames will arrive in the "OnCaptureVideo" // callback function of the VideoCapture class. Here you call the // display function to display the frame. // To stop the capture vidcap->StopCapture(); // If your job is over....just destroy it.. vidcap->Destroy();要使以上代码通过编译，你应该链接适当的库：
#pragma comment(lib,"vfw32") #pragma comment(lib,"winmm")
显示捕获的视频帧
有许多方法和API可以显示捕获的视频。你可以使用SetDIBitsToDevice()方法直接显示，但给予GDI的函数非常的慢。更好的方法是使用DrawDib API 显示。DrawDib函数为设备无关位图(DIBs)提供了高性能的图形绘制能力。DrawDib函数直接写入视频内存，因此性能更好。
以下代码摘要演示了使用DrawDib API显示视频帧。
// Initialize DIB for drawing... HDRAWDIB hdib=::DrawDibOpen(); // Then call this function with suitable parameters.... ::DrawDibBegin(hdib,...); // Now, if you are ready with the frame data, just invoke this // function to display the frame ::DrawDibDraw(hdib,...); // Finally, termination... ::DrawDibEnd(hdib); ::DrawDibClose(hdib);编解码库
// Initialize the compressor CParam cparams; cparams.format = CPARAM_QCIF; InitH263Encoder(&cparams); //If you need conversion from RGB24 to YUV420, call this InitLookupTable(); // Set up the callback function // OwnWriteFunction is the global function called during // encoding to return the encoded data... WriteByteFunction = OwnWriteFunction; // For compression, data must be in the YUV420 format... // Hence, before compression, invoke this method ConvertRGB2YUV(IMAGE_WIDTH,IMAGE_HEIGHT,data,yuv); // Compress the frame..... cparams.format = CPARAM_QCIF; cparams.inter = CPARAM_INTRA; cparams.Q_intra = 8; cparams.data=yuv; // Data in YUV format... CompressFrame(&cparams, &bits); // You can get the compressed data from the callback function // that you have registerd at the begining... // Finally, terminate the encoder // ExitH263Encoder();解码器：
//Initialize the decoder InitH263Decoder(); // Decompress the frame.... // > rgbdata must be large enough to hold the output data... // > decoder produces the image data in YUV420 format. After // decoding, it is converted into RGB24 format... DecompressFrame(data,size,rgbdata,buffersize); // Finaly, terminate the decoder ExitH263Decoder();如何运行程序
