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Re: [pwc] Auto Shutter and v4l2

To: Philips Webcam Linux Driver <>
Subject: Re: [pwc] Auto Shutter and v4l2
From: Hugo Costelha <>
Date: Wed, 9 Nov 2005 16:29:40 +0000
I was expecting the V4L2 API to have a V4L2_CID_AUTOEXPOSURE, similar to what 
happend with the gain control (where we have V4L2_CID_GAIN and 
V4L2_CID_AUTOGAIN), but that is not the case.

Given that, I would say than a different control would be wiser. It might even 
be that in future versions of the V4L2 API there would be an 
V4L2_CID_AUTOEXPOSURE, and then you would be (more) prepared already.

It would also make the code less proponent to peoples mistakes (using 0 as 
minimal instead of 1). But I'm not that expert, so it's just my opinion.

If you supplied a new (private) control, it would be something like 
V4L2_CID_PRIVATE_AUTOEXPOSURE, right?

Hugo

On Wednesday 09 November 2005 16:05, Luc Saillard wrote:
> On Fri, Nov 04, 2005 at 10:49:27AM +0000, Hugo Filipe Costelha De Castro 
wrote:
> > Hi,
> >
> > I am using a Philips Toucam Pro 740k.
> >
> > I see I can set the shutter speed using v4l2 control call  and
> > V4L2_CID_EXPOSURE. But how can I set the shutter to automatic? Usually we
> > would use the value -1 for automatic setting, but according to pwc-v4l.c,
> > the minimum value of V4L2_CID_EXPOSURE is 1.
>
> Ok, if i accept 0 as a value for automatic shutter speed, how every webcam
> will react ? Perhaps i need to create a new (private) control to setup the
> automatic gain. What do you think ?
>
> Luc
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