Re: [PATCH 0/10] MR4439: mfplat: Implement MFInitAMMediaTypeFromMFMediaType and related functions.

[Nikolay Sivov (＠nsivov)]

Nikolay Sivov (@nsivov) commented about dlls/mfplat/mediatype.c:
> - else if (IsEqualGUID(subtype, &MEDIASUBTYPE_YVYU))
> -
>    return &MFVideoFormat_YVYU;
> - else if (IsEqualGUID(subtype, &MEDIASUBTYPE_NV12))
> -
>    return &MFVideoFormat_NV12;
> - else
> -
> - base = *subtype;
> - base.Data1 = 0;
> -
> - if (memcmp(&base, &MFVideoFormat_Base, sizeof(base)))
> {
>     FIXME("Unknown subtype %s.\n", debugstr_guid(subtype));
>     return &null;
> }
> -
> - return subtype;

Could you explain why this is useful?