linux-kernel - Re: [PATCH 1/1] V4L: stk11xx, add a new webcam driver

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Date:	Mon, 28 May 2007 23:30:19 +0200
From:	Thierry Merle <thierry.merle@...e.fr>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
CC:	Markus Rechberger <mrechberger@...il.com>,
	video4linux-list@...hat.com, Jiri Slaby <jirislaby@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] V4L: stk11xx, add a new webcam driver

Mauro Carvalho Chehab a écrit :
>>> As Luca pointed, if we add conversion for one driver, we should add for
>>> the rest.
>>>
>>> Instead, it would be better if Jiri sends the decoding and the rescaling
>>> stuff as a patch to v4l2-apps/lib, starting the API decoding library.
>>> Once we have a library, we can ask the userspace developers to use it
>>> for the formats not recognized by their userspace apps.
>>>
>>>       
>> I think it would be better to evaluate existing solutions (eg. libpw).
>>     
>
> Agreed. Volunteers?
>
>   
Hi Mauro and Markus,
Just to summ up what I understood we need:

What do we need in userspace, only for v4l (dvb is not concerned):
- colorspace translations
- filters that be done in hardware if the selected hardware can, 
otherwise software plugin
- decompression algorithm like stk11xx or usbvision (the decompression 
algorithm is in kernelspace since it is of linear complexity but shall 
be moved to userspace)

Using pwlib will not mean that application developers will use pwlib to 
decode v4l driver outputs.
C bindings are much more popular than C++ bindings and do not prevent 
object oriented design.
Application developers implement their own codecs.
As an example, every application do deinterlacing internally or not...
Application developers will probably not use pwlib v4l extensions 
because they will prefer to write adapted codecs for their framework.

Much more important for me is to see the actual specification of the 
needed v4l extensions points, with advice/participation of 
application/codec developers.

Thierry
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