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

[Tomasz Figa <tfiga@chromium.org>]

On Fri, Nov 8, 2019 at 4:50 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
>
> On Thu, Nov 07, 2019 at 02:09:34PM +0100, Dmitry Sepp wrote:
> > Hello Gerd,
> >
> > Thank you for your feedback.
> >
> > There is no relationship between those. As I mentioned earlier. we have also
> > been working on a virtio video device at the same time. And there is no
> > relationship between the two specs.
>
> Keiichi, have you looked at the spec?
>
> I think it is useful to have a single device specification for all video
> functions given that there is a bunch of common stuff.  Both encoder and
> decoder must negotiate video frame and video stream parameters for
> example.  Also the virtio-video spec looks like a superset of
> virtio-vdec.
>
> Is there any important feature in video-vdec which is missing in
> virtio-video?
>

I just replied to Dmitry's email with further clarification on some
vdec aspects and rationale behind some of the design decisions. Please
take a look.

I think it should be possible to build one protocol for both decoding
and encoding. Actually virtio-vdec shouldn't need too much
modification to handle encoding. The ability to set operating mode
(decoder vs encoder) and set frame buffer format should be enough.

However I believe that making it as generic as virtio-video adds too
much complexity, increasing the possible attack surface and making it
difficult to validate.

Best regards,
Tomasz