Reading from One Stream and Writing to Another

The following example reads data from a stream, compresses it into a new stream, and writes the compressed data into a stream of a new file.

// SaveSmall - copies a stream of data from one file, compresses

// the stream, and writes the compressed stream to a new file.

//

// ps stream interface pointer

// lpFilename - new AVI file to build

//

void SaveSmall(PAVISTREAM ps, LPSTR lpFilename)

{ 

    PAVIFILE         pf;

    PAVISTREAM       psSmall;

    HRESULT          hr;

    AVISTREAMINFO    strhdr;

    BITMAPINFOHEADER bi;

    BITMAPINFOHEADER biNew;

    LONG             lStreamSize;

    LPVOID           lpOld;

    LPVOID           lpNew;

    // Determine the size of the format data using

    // AVIStreamFormatSize1.AQ75.

    AVIStreamFormatSize(ps, 0, &lStreamSize);

    if (lStreamSize > sizeof(bi)) // Format too large?

        return;

    lStreamSize = sizeof(bi);

    hr = AVIStreamReadFormat(ps, 0, &bi, &lStreamSize); // Read format

    if (bi.biCompression != BI_RGB) // Wrong compression format?

        return;

    hr = AVIStreamInfo(ps, &strhdr, sizeof(strhdr));

    // Create new AVI file using AVIFileOpen1_3JE9.

    hr = AVIFileOpen(&pf, lpFilename, OF_WRITE | OF_CREATE, NULL);

    if (hr != 0)

        return;

    // Set parameters for the new stream.

    biNew = bi;

    biNew.biWidth /= 2;

    biNew.biHeight /= 2;

    biNew.biSizeImage = ((((UINT)biNew.biBitCount * biNew.biWidth
                        + 31)&~31) / 8) * biNew.biHeight;

    SetRect(&strhdr.rcFrame, 0, 0, (int) biNew.biWidth,
            (int) biNew.biHeight);

    // Create a stream using AVIFileCreateStream4ULJ3E.

    hr = AVIFileCreateStream(pf, &psSmall, &strhdr);

    if (hr != 0) {             //Stream created OK? If not, close file.

        AVIFileRelease(pf);

        return;

    }

    // Set format of new stream using AVIStreamSetFormatD48A.C.

    hr = AVIStreamSetFormat(psSmall, 0, &biNew, sizeof(biNew));

    if (hr != 0) { 

        AVIStreamRelease(psSmall);

        AVIFileRelease(pf);

        return;

    }

    // Allocate memory for the bitmaps.

    lpOld = GlobalAllocPtr(GMEM_MOVEABLE, bi.biSizeImage);

    lpNew = GlobalAllocPtr(GMEM_MOVEABLE, biNew.biSizeImage);

    // Read the stream data using AVIStreamRead2.D1_I2.

    for (lStreamSize = AVIStreamStart(ps); lStreamSize <
        AVIStreamEnd(ps); lStreamSize++) { 

        hr = AVIStreamRead(ps, lStreamSize, 1, lpOld, bi.biSizeImage,
            NULL, NULL);

        //

        // Place error check here.

        //

        // Compress the data.

        CompressDIB(&bi, lpOld, &biNew, lpNew);

        // Save the compressed data using AVIStreamWriteK3D_6W.

        hr = AVIStreamWrite(psSmall, lStreamSize, 1, lpNew,
            biNew.biSizeImage, AVIIF_KEYFRAME, NULL, NULL);

    }

     // Close the stream and file.

    AVIStreamRelease(psSmall);

    AVIFileRelease(pf);

}