Extracting AVI Frames

Introduction

In the last project that I worked on, the project required to extract frames of an AVI movie and save them as bitmaps files. Here I want to share my experiences in this project with you.

AVIFile Functions

The best way to obtain information about AVI format and learn more about the internal behavior of the file, is going directly to MSDN as I did. The AVI related functions are inside vfw.h header file. This means you must include this header and add vfw32.lib library file to your project.

Here is the list of functions that I used in the project and a brief information about them (taken from MSDN):

Now it's time to write some code:

BOOL ExtractAVIFrames(CString szFileName)
{
    AVIFileInit();

    PAVIFILE avi;
    int res=AVIFileOpen(&avi, szFileName, OF_READ, NULL);

    if (res!=AVIERR_OK)
    {
        //an error occures
        if (avi!=NULL)
            AVIFileRelease(avi);
        
        return FALSE;
    }

    AVIFILEINFO avi_info;
    AVIFileInfo(avi, &avi_info, sizeof(AVIFILEINFO));

    CString szFileInfo;
    szFileInfo.Format("Dimention: %dx%d\n"
                      "Length: %d frames\n"
                      "Max bytes per second: %d\n"
                      "Samples per second: %d\n"
                      "Streams: %d\n"
                      "File Type: %d", avi_info.dwWidth,
                            avi_info.dwHeight,
                            avi_info.dwLength,
                            avi_info.dwMaxBytesPerSec,
                            (DWORD) (avi_info.dwRate / avi_info.dwScale),
                            avi_info.dwStreams,
                            avi_info.szFileType);

    AfxMessageBox(szFileInfo, MB_ICONINFORMATION | MB_OK);

    PAVISTREAM pStream;
    res=AVIFileGetStream(avi, &pStream, streamtypeVIDEO /*video stream*/, 
                                               0 /*first stream*/);

    if (res!=AVIERR_OK)
    {
        if (pStream!=NULL)
            AVIStreamRelease(pStream);

        AVIFileExit();
        return FALSE;
    }

    //do some task with the stream
    int iNumFrames;
    int iFirstFrame;

    iFirstFrame=AVIStreamStart(pStream);
    if (iFirstFrame==-1)
    {
        //Error getteing the frame inside the stream

        if (pStream!=NULL)
            AVIStreamRelease(pStream);

        AVIFileExit();
        return FALSE;
    }

    iNumFrames=AVIStreamLength(pStream);
    if (iNumFrames==-1)
    {
        //Error getteing the number of frames inside the stream
        
        if (pStream!=NULL)
            AVIStreamRelease(pStream);
        
        AVIFileExit();
        return FALSE;
    }

    //getting bitmap from frame
    BITMAPINFOHEADER bih;
    ZeroMemory(&bih, sizeof(BITMAPINFOHEADER));

    bih.biBitCount=24;    //24 bit per pixel
    bih.biClrImportant=0;
    bih.biClrUsed = 0;
    bih.biCompression = BI_RGB;
    bih.biPlanes = 1;
    bih.biSize = 40;
    bih.biXPelsPerMeter = 0;
    bih.biYPelsPerMeter = 0;
    //calculate total size of RGBQUAD scanlines (DWORD aligned)
    bih.biSizeImage = (((bih.biWidth * 3) + 3) & 0xFFFC) * bih.biHeight ;

    PGETFRAME pFrame;
    pFrame=AVIStreamGetFrameOpen(pStream, 
           NULL/*(BITMAPINFOHEADER*) AVIGETFRAMEF_BESTDISPLAYFMT*/ /*&bih*/);
    
    //Get the first frame
    int index=0;
    for (int i=iFirstFrame; i<iNumFrames; i++)
    {
        index= i-iFirstFrame;

        BYTE* pDIB = (BYTE*) AVIStreamGetFrame(pFrame, index);
        
        CreateFromPackedDIBPointer(pDIB, index);
    }

    AVIStreamGetFrameClose(pFrame);

    //close the stream after finishing the task
    if (pStream!=NULL)
        AVIStreamRelease(pStream);

    AVIFileExit();

    return TRUE;
}

The only one function that I must describe more about is: CreateFromPackedDIBPointer(). This function takes a pointer returned from AVIStreamGetFrame() function and creates a bitmap from it. As you know, the AVIStreamGetFrame() returns a pointer to DIB information about the frame. We take this pointer and create a bitmap from it.

BOOL CreateFromPackedDIBPointer(LPBYTE pDIB, int iFrame)
{
    ASSERT(pDIB!=NULL);

    //Creates a full-color (no palette) DIB from a pointer to a
    //full-color memory DIB

    //get the BitmapInfoHeader
    BITMAPINFOHEADER bih;
    RtlMoveMemory(&bih.biSize, pDIB, sizeof(BITMAPINFOHEADER));

    //now get the bitmap bits
    if (bih.biSizeImage < 1)
    {
        return FALSE;
    }

    BYTE* Bits=new BYTE[bih.biSizeImage];

    RtlMoveMemory(Bits, pDIB + sizeof(BITMAPINFOHEADER), bih.biSizeImage);

    //and BitmapInfo variable-length UDT
    BYTE memBitmapInfo[40];
    RtlMoveMemory(memBitmapInfo, &bih, sizeof(bih));

    BITMAPFILEHEADER bfh;
    bfh.bfType=19778;    //BM header
    bfh.bfSize=55 + bih.biSizeImage;
    bfh.bfReserved1=0;
    bfh.bfReserved2=0;
    bfh.bfOffBits=sizeof(BITMAPINFOHEADER) + sizeof(BITMAPFILEHEADER); //54
    
    CString FileName;
    FileName.Format("Frame-%05d.bmp", iFrame);
    
    FILE* fp=fopen(FileName, "wb");
    if (fp!=NULL)
    {
        fwrite(&bfh, sizeof(bfh), 1, fp);
        fwrite(&memBitmapInfo, sizeof(memBitmapInfo), 1, fp);
        fwrite(Bits, bih.biSizeImage, 1, fp);
        fclose(fp);
    }
    else
    {
        TRACE0(_T("Error writing the bitmap file"));
        return FALSE;
    }

    delete [] Bits;
    return TRUE;
}

Enjoy!