void OnReadData(ILMDVRSource* pSource) { double startOffset = 0; long minSize = 0; long maxSize = 4096; DWORD dwUserData = 0; BYTE *pData = malloc(4096); long sizeRead; ILMDVRSource_ReadData (pSource, startOffset, minSize, maxSize, dwUserData, pData, &sizeRead); free(pData); }