DirectShow : AVI文件操作 -- C++ 类

DirectShow  AVI 文件操作

最近在做一个“运动物体分割”的课题，在课题中要处理视频文件，首先考虑最简单的视频格式：AVI格式，由于AVI格式是微软推出的，所以在Windows下操作比较容易，这里我用DirectShow读写AVI视频文件，并把所有操作封装成一个类：AVICodec。下面是类的定义：

class AVICodec
{
public:
 AVICodec(){size = -1;}
 AVICodec(LPCWSTR avifile);
 void release();
 int init_getframe();
 char* getframe(unsigned int index);
 int getFrame(unsigned int index);
 int getFrameEnd();
 void play();
private:
 IGraphBuilder *pGraph;
 IMediaControl *pControl;
 IMediaEvent   *pEvent;
 IMediaDet   *pDet;

 AM_MEDIA_TYPE amMediaType;
public:
 BITMAPINFOHEADER *pbih;
 double fps, length;
 unsigned int nFrame;
 long size;
 bool is_begin;
 char * pBuffer;
private:
 char * buf;
};

这个类目前实现两个功能：

1. 播放AVI文件      play()
2. 获取指定帧的数据，返回数据是RGB24格式 GetFrame()

下面给出代码：

AVICodec::AVICodec(LPCWSTR avifile)//类初始化，avifile是文件名
{
 pGraph  = NULL;
 pControl = NULL;
 pEvent  = NULL;
 size  = -1;
 is_begin = false;
 buf   = NULL;
 HRESULT hr = CoInitialize(NULL);
 if(FAILED(hr)){
  cout<<"initialize COM Library failed"<<endl;
  exit(0);
 }
 hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER,
                        IID_IGraphBuilder, (void **)&pGraph);
 if(FAILED(hr)){
  cout<<"could not create Filter Graph Manager"<<endl;
  exit(0);
 }
 hr = pGraph->QueryInterface(IID_IMediaControl, (void **)&pControl);
    hr = pGraph->QueryInterface(IID_IMediaEvent, (void **)&pEvent);
 hr = pGraph->RenderFile(avifile, NULL);
 if(FAILED(hr)){
  cout<<"open AVI file failed"<<endl;
  exit(0);
 }
 hr = CoCreateInstance(CLSID_MediaDet, NULL, CLSCTX_INPROC, IID_IMediaDet,
  (void **)&pDet);
 if(FAILED(hr)){
  cout<<"initialize MediaDet Failed"<<endl;
  exit(0);
 }
 hr = pDet->put_Filename(BSTR(avifile));
 if(FAILED(hr)){
  cout<<"MediaDet put file failed"<<endl;
  exit(0);
 }
}

int AVICodec::init_getframe()//抓图的初始化，得到帧数，帧频等参数
{
 long lStreams;
 HRESULT hr = pDet->get_OutputStreams(&lStreams);
 if(FAILED(hr)){
  cout<<"Failed : pDet->get_OutputStreams()"<<endl;
  return -1;
 }
 
 hr = pDet->put_CurrentStream(0);
 if(FAILED(hr)){
  cout<<"Failed : pDet->put_CurrentStream()"<<endl;
  return -1;
 }
 hr = pDet->get_StreamMediaType(&amMediaType);
 if(FAILED(hr)){
  cout<<"Failed : pDet->get_StreamMediaType()"<<endl;
 }
 pbih = &((VIDEOINFOHEADER *)amMediaType.pbFormat)->bmiHeader;
 if(FAILED(pDet->get_FrameRate(&fps)) || FAILED(pDet->get_StreamLength(&length)))
 {
  cout<<"Failed : pDet->get_FrameRate() || pDet->get_StreamLength()"<<endl;
  return -1;
 }
 nFrame = (unsigned int)(length * fps);
 return 1;
}

int AVICodec::getFrame(unsigned int index)//抓取index帧的图像，存放在buf中
{
 if(index>nFrame){
  cout<<"exceed max frame index"<<endl;
  return -1;
 }
 HRESULT hr;
 double position = (double)(index*1.0/fps);
 
  hr = pDet->GetBitmapBits(position,&size,NULL,pbih->biWidth,pbih->biHeight);
  if(FAILED(hr)){
   cout<<"Failed : pDet->GetBitmapBits()"<<endl;
   return -1;
  }
 if(is_begin==false){
  buf = new char[size];
  memset(buf,0,size);
  is_begin = true;
 }
 //memset(buf,0,size);
 hr = pDet->GetBitmapBits(position, NULL, buf, pbih->biWidth, pbih->biHeight);
 BITMAPINFO *binfo = (BITMAPINFO *)buf;
 pBuffer = buf + ((BITMAPINFO *)buf)->bmiHeader.biSize;
 if(FAILED(hr)){
  cout<<"Failed : pDet->GetBitmapBits()"<<endl;
  return -1;
 }
 return 1;
}

int AVICodec::getFrameEnd()//抓图后释放内存
{
 is_begin = false;
 delete[] buf;
 return 1;
}

void AVICodec::play()//播放AVI文件，文件名在类初始化时给定
{
 HRESULT hr = pControl->Run();
 if(SUCCEEDED(hr)){
  long evCode;
  pEvent->WaitForCompletion(INFINITE,&evCode);
 }
}

void AVICodec::release()//运行完释放资源
{
 pControl->Release();
 pEvent->Release();
 pControl->Release();
 pDet->Release();
 CoUninitialize();
}

目前这个类还在充实中，后续的代码会不断更新。

如果程序中有什么问题，还望指教