On 29-May-01 Jeroen Vreeken wrote:
> On 2001.05.30 11:47:23 +0200 Brad Hards wrote:
>> Without knowing the details, I risk making a fool of myself, but would it
>>
>> be possible to use a similar approach to gpm? So we use a named pipe or
>> similar in user space, generated by vfm (video format manager:).
>> General idea is
>> device driver exports to kernel V4L
>> kernel V4L exports to userspace on /dev/videodataXX
>> userspace daemon opens /dev/videodataXX and munges formats to
>> /dev/videoXX
>> old style clients use /dev/videoXX (hopefully without much change)
>> new style clients use /dev/videodataXX
I would reverse the names, making the �old style� videodevices something
like /dev/fmtvideoXX (formatted video), and �new style� would be
/dev/videoXX. Otherwise nobody would notice and nothing would ever get done.
Most tools allow you to specify which video device to use with a command
line parameter (or dropdown box, with my own camstream :-)), so that�s not a
problem. Should that not be possible, nothing you cannot fix without a
symlink :)
It would be something of a hack though; the ftmvideoXX and videoXX would
essentially be twins, not akin to the ttyS/cua pairs. Opening video0 would
block fmtvideo0, and vice versa.
I�m thinking... We could create the conversion routine as a module; as soon
as the module is loaded, the fmtvideoXX devices �appear�; the videoXX devices
would alwas be present.
>> Not very clean, but at least a migration path.
*nod* One of the better solutions I�ve heard sofar.
>> Brad
>
> Whats wrong with:
> old style clients use /dev/videoXX (and are on their own)
> new style clients ask userspace lib to open /dev/videoXX and deliver them
> data in the right format.
>
> The lib just has to capture and (if the hardware can't) convert the data
> to format the user wants.
The fact that an estimated 80% of tools right now are �old style� clients
and would therefor break? Furthermore, some tools would only work with
certain webcams because they happen to deliver the right format.
However, I�m now working on a (shared) library definition for color
conversion; maybe the idea catches on and we can finally get some things
implemented and moving.
- Nemosoft
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