[camerabin] buggy webcams with no autoexposure

[Alexey Fisher]

Hi,
i thing camerabin is the right place to discuss this problem,

some build in webcams on some laptops provide only static framereate
without autoexposure. With 30fps i get goot frame rate but bad image,
with 10fps i get good picture, but camerabin will take 30fps by default.

For example the cam on fujisu lifebook a530 is more tricky. It support
only 30fps on 640x480 frame size and about 9fps on 1280x1024. So to get
good picture for video chat i should do fallowing workaround:

gst-launch-0.10 v4l2src ! ffmpegcolorspace !
video/x-raw-yuv,width=1280,height=1024,framerate=9/1 ! videoscale !
video/x-raw-yuv,width=320,height=240 ! fpsdisplaysink

I have fallowing questions:
How can we find if the cam is buggy? Add v4l2_ctrl_quirk? Or if cam do
nor have exposure controls this mean it use static exposure time?
For video chat we need not more than 15fps, so if we have only choice
between 30fps and 10fps, best decision will be probably 10fps.

Less fps -> less videotmpnoise -> better image quality -> less load for
encoder -> less traffic.
--
Regards,
        Alexey


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[Thiago Sousa Santos]

On Sun, 2011-01-16 at 10:37 +0100, Alexey Fisher wrote:

> Hi,
> i thing camerabin is the right place to discuss this problem,
>
> some build in webcams on some laptops provide only static framereate
> without autoexposure. With 30fps i get goot frame rate but bad image,
> with 10fps i get good picture, but camerabin will take 30fps by default.
>
> For example the cam on fujisu lifebook a530 is more tricky. It support
> only 30fps on 640x480 frame size and about 9fps on 1280x1024. So to get
> good picture for video chat i should do fallowing workaround:
>
> gst-launch-0.10 v4l2src ! ffmpegcolorspace !
> video/x-raw-yuv,width=1280,height=1024,framerate=9/1 ! videoscale !
> video/x-raw-yuv,width=320,height=240 ! fpsdisplaysink
>
> I have fallowing questions:
> How can we find if the cam is buggy? Add v4l2_ctrl_quirk? Or if cam do
> nor have exposure controls this mean it use static exposure time?
> For video chat we need not more than 15fps, so if we have only choice
> between 30fps and 10fps, best decision will be probably 10fps.

My suggestion here is to have these possible caps ordered and make
camerabin prefer the first structure on caps.

In any case, this looks tricky to represent in caps in a generic way.
You could solve that at application level.

>
> Less fps -> less videotmpnoise -> better image quality -> less load for
> encoder -> less traffic.

--
Thiago


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