State of Linux webcam support

[Thierry Merle]

Hi Jiri,

Jiri Slaby a écrit :
> On 09/28/2007 02:13 PM, Bertrik Sikken wrote:
>   
>> Hi all,
>>
>> A couple of years ago I worked on getting some webcams working
>> with Linux. To be honest, I was unpleasantly surprised.
>> There seems to be a lack of direction on how webcams
>> are even supposed to be supported.
>>
>> The problem is that many USB webcams send raw 'bayer' sensor
>> data in a compressed form to the PC in order to get reasonable
>> frames-per-second over a full-speed (12 Mb/s) USB connection
>> AFAIK, the linux kernel developers decided that is was no longer
>> allowed to do decompression and bayer format conversion in the kernel.
>>     
>
> Exactly.
>
>   
>> Some ideas:
>> * create a user-space library for webcams that reads the compressed
>>   data from a v4l(2) device file, decompresses and unbayers it,
>>   then exposes it through a standard API to applications.
>>     
>
> This idea is already in progress: v4l library. [Needed also for stk11xx (only in
> -mm due to not having yet another bayer->rgb conversion in the kernel) and
> usbvision (in v4l yet).]
>
> Thierry Merle <thierry.merle at free.fr>:
> http://thierry.merle.free.fr/v4l2_extension/general.html
>
> regards,
>   
Thanks for pointing it.
The spec has moved on linuxtv: 
http://www.linuxtv.org/v4lwiki/index.php/V4L2UserspaceLibrary

The code skeleton is not yet finished but advancing slowly.
If you do not understand something in the spec, please tell me. It is 
perfectible I am sure.
The basic idea to have a basic driver that would provide compressed 
video frames, and a virtual driver (the v4l extended driver) that would 
uncompress these videoframes with the help of a userspace daemon.
I am currently writing the userspace daemon interface, this corresponds 
to the step 'Control the hardware' in the spec.

Cheers,
Thierry