On Sat, 27 Jan 2001, Gerd Knorr wrote:
> In lists.linux.v4l, you wrote:
> >
> > For a bt848, when are the risc program(s) generated? When REQBUFS is called,
> > or when VIDIOC_QBUF is called?
>
> QBUF.
Isn't that inefficient? Last time I checked, risc program generation takes
a significant length of time.
> > > Packed pixel formats can use the v4l2_pix_format.bytesperline to
> > > specify any padding they want. Planar formats can't have padding
> > > (any objections on this? If so: why? I can't think of any useful
> > > application for this...).
> >
> > What if you want to overlay the video into a larger image, except you're
> > using planar mode?
>
> Any reason to do that with a planar video format?
>
> The main reason I see to have some padding is that you provide video data
> for some other piece of hardware (vga for ewample) where you might have
> some constrains on what the hardware allows you / you want to put that
That was my thought. Someone might have hardware that wants a planar overlay.
> > What about clipping?
>
> ??? We are talking about capture here, not screen overlay...
Why would you never want clipping in capture? You might want to capture just
a sub-region of the picture. For instance checking if the lights are out on a
camera, you might just capture a few small portions of the image to see if
they are black.
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