Varying frame rate

Varying frame rate

[Haavard Holm]

Hello,

  I am writing an application that capture video/pictures from a webcam.
My program is built on moinejf.free.fr/*svv*.*c*
which again is built on v4l2spec.bytesex.org/v4l2spec/*capture*.*c*

OS is linux 2.6.29.6-217.2.3.fc11.x86_64
Webcam is "Logitech Quickcam Pro for Notebooks" (046d:0991)

My obeservation is : Depending on what my camera focus on, the framerate
varies from 5 to 15 fps. I have tried several times, same result.

Why is that. How can I avoid this ?

Best regards

Håvard Holm

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Re: Varying frame rate

[Maxim Levitsky]

On Sat, 2009-08-15 at 23:48 +0200, Haavard Holm wrote:
> Hello,
> 
>   I am writing an application that capture video/pictures from a webcam.
> My program is built on moinejf.free.fr/*svv*.*c*
> which again is built on v4l2spec.bytesex.org/v4l2spec/*capture*.*c*
> 
> OS is linux 2.6.29.6-217.2.3.fc11.x86_64
> Webcam is "Logitech Quickcam Pro for Notebooks" (046d:0991)
> 
> My obeservation is : Depending on what my camera focus on, the framerate
> varies from 5 to 15 fps. I have tried several times, same result.
> 
> Why is that. How can I avoid this ?
I have observed similar issues with uvc camera on my aspire one (low
frame rate while the illumination is low)

Probably this is a hardware issue, and maybe there is a control to turn
this off.

Best regards,
	Maxim Levitsky


> 
> Best regards
> 
> Håvard Holm
> 
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Re: Varying frame rate

[Jean-Francois Moine]

On Sun, 16 Aug 2009 03:43:52 +0300
Maxim Levitsky <maximlevitsky@gmail.com> wrote:

> On Sat, 2009-08-15 at 23:48 +0200, Haavard Holm wrote:
	[snip]
> > My obeservation is : Depending on what my camera focus on, the
> > framerate varies from 5 to 15 fps. I have tried several times, same
> > result.
	[snip]
> I have observed similar issues with uvc camera on my aspire one (low
> frame rate while the illumination is low)
> 
> Probably this is a hardware issue, and maybe there is a control to
> turn this off.

Hello,

The frame rate depends on the exposure time. If auto exposure is set,
you may have such a behaviour.

Best regards.

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Ken ar c'hentañ	|	      ** Breizh ha Linux atav! **
Jef		|		http://moinejf.free.fr/

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Re: Varying frame rate

[Maxim Levitsky]

On Sun, 2009-08-16 at 08:03 +0200, Jean-Francois Moine wrote:
> On Sun, 16 Aug 2009 03:43:52 +0300
> Maxim Levitsky <maximlevitsky@gmail.com> wrote:
> 
> > On Sat, 2009-08-15 at 23:48 +0200, Haavard Holm wrote:
> 	[snip]
> > > My obeservation is : Depending on what my camera focus on, the
> > > framerate varies from 5 to 15 fps. I have tried several times, same
> > > result.
> 	[snip]
> > I have observed similar issues with uvc camera on my aspire one (low
> > frame rate while the illumination is low)
> > 
> > Probably this is a hardware issue, and maybe there is a control to
> > turn this off.
> 
> Hello,
> 
> The frame rate depends on the exposure time. If auto exposure is set,
> you may have such a behaviour.
Exactly, that is what I was trying to say, but didn't...

Best regards,
	Maxim Levitsky

> 
> Best regards.
> 

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Re: Varying frame rate

[Haavard Holm]

On 08/16/2009 08:03 AM, Jean-Francois Moine wrote:
> On Sun, 16 Aug 2009 03:43:52 +0300
> Maxim Levitsky<maximlevitsky@gmail.com>  wrote:
>
>    
>> On Sat, 2009-08-15 at 23:48 +0200, Haavard Holm wrote:
>>      
> 	[snip]
>    
>>> My obeservation is : Depending on what my camera focus on, the
>>> framerate varies from 5 to 15 fps. I have tried several times, same
>>> result.
>>>        
> 	[snip]
>    
>> I have observed similar issues with uvc camera on my aspire one (low
>> frame rate while the illumination is low)
>>
>> Probably this is a hardware issue, and maybe there is a control to
>> turn this off.
>>      
> Hello,
>
> The frame rate depends on the exposure time. If auto exposure is set,
> you may have such a behaviour.
>    

 From a c-program - how do I turn off auto exposure ?

Best

Håvard Holm
> Best regards.
>
>    

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Re: Varying frame rate

[Jean-Francois Moine]

On Sun, 16 Aug 2009 10:35:56 +0200
Haavard Holm <haavard.holm@ntnu.no> wrote:
	[snip]
> > The frame rate depends on the exposure time. If auto exposure is
> > set, you may have such a behaviour.
> >    
> 
>  From a c-program - how do I turn off auto exposure ?

You may do it by the VIDIOC_S_CTRL ioctl (look at
v4l2-apps/util/v4l2-ctl.cpp in the LinuxTv mercurial main repository)

Otherwise, by program, I know about v4l2ucp or vlc (1.0.x).

Best regards.

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Jef		|		http://moinejf.free.fr/

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RE : Varying frame rate

[Jonathan Lafontaine]

Hi, I want to know what is the new procedure or 

email adress for the new V4L newsletter?
________________________________________
De : video4linux-list-bounces@redhat.com [video4linux-list-bounces@redhat.com] de la part de Jean-Francois Moine [moinejf@free.fr]
Date d'envoi : 16 août 2009 05:09
À : video4linux-list@redhat.com
Objet : Re: Varying frame rate

On Sun, 16 Aug 2009 10:35:56 +0200
Haavard Holm <haavard.holm@ntnu.no> wrote:
        [snip]
> > The frame rate depends on the exposure time. If auto exposure is
> > set, you may have such a behaviour.
> >
>
>  From a c-program - how do I turn off auto exposure ?

You may do it by the VIDIOC_S_CTRL ioctl (look at
v4l2-apps/util/v4l2-ctl.cpp in the LinuxTv mercurial main repository)

Otherwise, by program, I know about v4l2ucp or vlc (1.0.x).

Best regards.

--
Ken ar c'hentañ |             ** Breizh ha Linux atav! **
Jef             |               http://moinejf.free.fr/

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