用VC编写点对点视频会议程序

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->PostThreadMessageWM_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。