On Wed October 17 2012 02:25:00 Laurent Pinchart wrote:
> Hi Hans,
>
> On Monday 15 October 2012 13:35:45 Hans Verkuil wrote:
> > During the Plumbers Conference a few weeks ago we had a session to resolve
> > V4L2 ambiguities. It was very successful, but we didn't manage to tackle
> > two of the harder topics, and a third one (timestamps) cause a lot of
> > discussion on the mailinglist after the conference.
> >
> > So here is the list I have today. Any other ambiguities or new features that
> > should be added to the list?
>
> Small topic that we've briefly discussed on IRC: if a device doesn't tell the
> driver what color space it uses, should the driver guess or tell the
> application that the color space is unknown ? I've ran into that issue for
> the
> uvcvideo driver, while I agree with you that in that case the color space is
> very likely sRGB, and that the driver is probably in a better position to
> make
> that guess than the userspace application (as the driver knows it handles a
> webcam), what should be the rule ?
I'll add it to the list.
> > 1) Make a decision how to tell userspace that the monotonic timestamp is
> > used.
> >
> > Several proposals were made, but no decision was taken AFAIK. Can someone
> > (Sakari?) make a summary/current status of this?
> >
> >
> > 2) Pixel Aspect Ratio
> >
> > Pixel aspect: currently this is only available through VIDIOC_CROPCAP. It
> > never really belonged to VIDIOC_CROPCAP IMHO. It's just not a property of
> > cropping or composing. It really belongs to the input/output timings (STD
> > or DV_TIMINGS). That's where the pixel aspect ratio is determined.
> >
> > While it is possible to add it to the dv_timings struct, I see no way of
> > cleanly adding it to struct v4l2_standard (mostly because VIDIOC_ENUMSTD is
> > now handled inside the V4L2 core and doesn't call the drivers anymore).
>
> Isn't that an implementation issue instead of an API issue ?
True, but it will require changing all drivers. But adding it to v4l2_standard
would be the best place for this, so perhaps we should think about doing all
this work.
Regards,
Hans
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