Re: [virtio-dev] [RFC RESEND] virtio-video: Add virtio video device specification

[Keiichi Watanabe <keiichiw@chromium.org>]

Hi,

Thanks Tomasz and Gerd for the suggestions and information.

On Tue, Dec 17, 2019 at 10:39 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
>
>   Hi,
>
> > On the host side, the encode and decode APIs are different as well, so
> > having separate implementation decoder and encoder, possibly just
> > sharing some helper code, would make much more sense.
>
> When going down that route I'd suggest to use two device ids (even when
> specifying both variants in one spec section and one header file due to
> the overlaps) instead of feature flags.

Sounds good. It makes sense to use different device IDs for different devices.

>
> > > I don't think using fourcc is a problem, and given that both drm and
> > > v4l2 use fourcc already this would be a good choice I think.
> >
> > Both DRM and V4L2 use two mutually incompatible sets of FourCCs, so
> > I'm not sure how it could be a good choice. At least unless we decide
> > to pick a specific set of FourCC. It doesn't help that Windows/DirectX
> > has its own set of FourCCs that's again slightly different than the
> > two mentioned before.
>
> Ouch, wasn't aware of that.  That makes reusing fourcc codes much less
> useful.
>
> > > But the definition should be more specific than just "fourcc".  Best
> > > would be to explicitly list and define each format supported by the
> > > spec.
> >
> > Why not be consistent with virtio-gpu and just define new formats as
> > we add support for them as sequential integers?
>
> Yes, lets do that.
>

It makes sense. I seems to have overestimated FourCC.

Best,
Keiichi

> cheers,
>   Gerd
>