[gst-devel] Info on webcam parameters detected by gstreamer

Stefan Kost ensonic at hora-obscura.de
Mon Jun 21 16:59:20 CEST 2010

On 15.06.2010 09:14, Nicolas Bertrand wrote:
> Hi,
> I'm trying to understand the parameters, given by gstreamer , for webcam
> ( as mimetypes, definition, colorspace, etc ...)
> I want to develop an app. to control those parameters, and allow user to
> change it ( goal : best image quality, aspect ratio, CPU consumption,
> etc...)
> Those parameters  types change according webcam manufacturers. So how
> gstreamer deals with that ?  Is retrieved from the webcam , but
> according which protocol ?  Is there a standard  specification ? This is
> done by gstreamer or v4l ?
> I look for some 'hints', doc  or what portion of code to understand how
> communication  and paramters exchange with webcam works.
Look at the code :) On linux gstreamer uses v4l2. This is supposed to be
the interface that provides hardware abstraction. The v4l2src element
uses the v4l2 api to query the device capabilities as soon as the device
has been opened and set the caps on the src pad then.  You can examine
those from your application to e.g. show resolutions and framerates. 
Not sure what you wants to change in regard to CPU consumtions though.


> Thanks in advance
> Nico
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