v4l interface questions

v4l interface questions

[Pavel Machek]

Hi!

I have few questions about v4l api.

I have device (vicam == usb 3com homeconnect camera), which would like to
fit into v4l framework. But... mmap is not really native operation for
usb. Should I emulate it, or just return unsupported and expect
applications to use read()?

Similar problem is there with formats. vicam has some really strange
formats. Should I do conversion in kernel?

Is there some usermode program that can handle camera without mmap
ability and can support arbitrary screen sizes + 16bpp grayscale?
								Pavel
-- 
I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org

Re: v4l interface questions

[Steven Walter]

On Mon, Aug 27, 2001 at 11:11:26PM +0200, Pavel Machek wrote:
> I have device (vicam == usb 3com homeconnect camera), which would like to
> fit into v4l framework. But... mmap is not really native operation for
> usb. Should I emulate it, or just return unsupported and expect
> applications to use read()?
> 
> Similar problem is there with formats. vicam has some really strange
> formats. Should I do conversion in kernel?

Don't do conversion in the kernel.

> Is there some usermode program that can handle camera without mmap
> ability and can support arbitrary screen sizes + 16bpp grayscale?
-- 
-Steven
In a time of universal deceit, telling the truth is a revolutionary act.
			-- George Orwell

Re: v4l interface questions

[Gerd Knorr]

Pavel Machek wrote:
>  Hi!
>  
>  I have few questions about v4l api.
>  
>  I have device (vicam == usb 3com homeconnect camera), which would like to
>  fit into v4l framework. But... mmap is not really native operation for
>  usb. Should I emulate it, or just return unsupported and expect
>  applications to use read()?

IHMO applications should be able to fallback to read() if mmap() doesn't
work.

>  Similar problem is there with formats. vicam has some really strange
>  formats. Should I do conversion in kernel?

Probably.  The driver should support at least one of the standard
VIDEO_PALETTE_* formats.  It is fine to pick one which comes close to
the native format of the camera, there is no need to support _all_
formats.

>  Is there some usermode program that can handle camera without mmap
>  ability and can support arbitrary screen sizes + 16bpp grayscale?

8bpp grayscale should be no problem with xawtv.  I'd suspect you will
not find any app which can deal with 16bpp, there isn't even a
VIDEO_PALETTE_* #define for this ...

  Gerd

-- 
Damn lot people confuse usability and eye-candy.