Nikolay Sivov (@nsivov) commented about dlls/mfplat/main.c:
IMFAttributes_GetAllocatedString(attributes, &MF_BYTESTREAM_ORIGIN_NAME, &urlW, &length); url = urlW; }
if (!url)
{
IMFAttributes_GetAllocatedString(attributes, &MF_BYTESTREAM_EFFECTIVE_URL, &urlW, &length);
url = urlW;
} IMFAttributes_Release(attributes);
I don't see this being used by e.g. CreateObjectFromByteStream(). How did you check that? I tried by removing MF_BYTESTREAM_ORIGIN_NAME and setting this MF_BYTESTREAM_EFFECTIVE_URL. Resolution fails for me.