Re: [PATCH 2/4 v4] i.MX31: Image Processing Unit DMA and IRQdrivers

From: Sascha Hauer
Date: Tue Dec 23 2008 - 07:08:29 EST


On Tue, Dec 23, 2008 at 02:32:08PM +0300, Dmitry Krivoschekov wrote:
> Sascha Hauer wrote:
> > On Tue, Dec 23, 2008 at 01:09:10PM +0300, Dmitry Krivoschekov wrote:
> >> Robert Schwebel wrote:
> >>> On Mon, Dec 22, 2008 at 07:37:53PM +0100, Sascha Hauer wrote:
> >>>> Another thing is the overlay framebuffer. I think it's mainly useful
> >>>> to display video streams.
> >>> Right. The idea is that you can push a video stream into /dev/fb1 (for
> >>> example by using the gstreamer fbdev sink) while displaying widgets from
> >>> a GUI toolkit on /dev/fb0.
> >>>
> >>>> Maybe it's better to implement this as a v4l device as unlike the
> >>>> framebuffer API the v4l API is designed to handle different image
> >>>> buffers.
> >>> Huh? v4l is image-frames-to-userspace, not vice versa.
> >>>
> >> ...and vice versa too, v4l2 is not about input devices only but it is
> >> also related to output devices, v4l2 spec even has a special chapter
> >> dedicated to overlays [1]. Moreover, you can find such a driver within
> >> Freescale's BSP [2]. Another example is Omap's videoout driver [3].
> >
> > Are you aware of any application making use of this feature?
>
> IIRC, mplayer is able to output on a v4l2 device.

Yes, but only on some MPEG decoder cards. Raw frames are not supported.

> Also, Freescale's
> i.MX31 ADS BSP contained a bunch of V4L2 unit tests, including v4l2 output.

Ah ok, didn't know that

Sascha

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