Re: [GnomeMeeting-list] km v4l module and gnomemeeting (additional info)
- From: Damien Sandras <dsandras seconix com>
- To: gnomemeeting-list gnome org
- Subject: Re: [GnomeMeeting-list] km v4l module and gnomemeeting (additional info)
- Date: 22 Jul 2003 23:12:28 +0200
Le jeu 17/07/2003 à 10:09, Francesco a écrit :
> I asked this in the GATOS mailing list (they develop the v4l module for my video capture card) and they answered me:
> > When I run gnomemeeting it detects the /dev/video0 device, but when it
> > tryes to initialize it it says "Error with the frame size."
> Fix gnomemeeting so that it agrees to use the size which the
> hardware is capable of. Also, it would probably be necessary
PWLib is trying them all, if it doesn't work, then it probably means
that the GATOS driver doesn't fully respect the v4l API or that there is
a bug in PWLib.
Anyway, what you can do is edit the file pwlib/src/ptlib/video4linux.cxx
and look for the tips. Then you can add a tip to pwlib for your
particular driver. It will work, but it will require your help. Once you
know what tip to add (it is self-explaining), I can commit it to their
> to teach it not to try to transfer what it gets from /dev/video0
> to videocard (as it would do in case of a separate grabber)
> and perhaps lots of other fixes.
> Another question not directly related with gnomemeeting from Richard Smith in their mailing list and the answer:
> > Km claims provide to provide a Video4Linux interface however things
> > like NVrec don't seem to work. I seem to remember reading somewhere
> > that only ffmpeg is supported. Nikolai Zhubr's patches claim to make
> > km play nicer with other v4l program (specifically mp1e) but NVrec still
> > fails with a feature unsuported error.
> > If km is a v4l interface why are the patches necessary? What's the
> > difference between a full v4l device and gatos?
> The key issue here is that v4l was developed for standalone grabber cards,
> which AIW cards are not.
> Many programs using v4l assume that the card they are talking to is bt84x
> and try to access such things as tuner, etc.
> With GATOS, the card control is performed from within XFree86 driver, and
> km is an auxiliary device only - when you try to open it it checks which
> settings have been programmed into AIW and provides video stream based on
> them. It does not turn video on or off and does not change anything else.
> The only part it touches are DMA and interrupt registers and these are not
> used by Xserver. Much effort was spent to get it to coexist peacefully
> with Radeon DRM (3d acceleration) module.
> A common impulse people have when they see this is "ok, let me make this a
> pure v4l module". Many have tried, even went as far as implementing kernel
> i2c driver, but no functional module (i.e. one that actually captures) was
> Simple as is, km was quite tricky to get right. I believe, that much time
> savings resulted from reducing the code within km and performing most of
> the settings in user space.
> One more thing: km produces stream of interlaced fields, not frames,
> exactly as it recieves them from decoder. Thus recommended settings for
> AVview are half-rate (thus skipping every other field) and either
> half-width (i.e. decimation of in x direction) or double-interpolate
> (interpolation in y direction).
> What I ask now is if it will be ever possible to use gnomemeeting with this v4l module.
> Thanks for support.
> GnomeMeeting-list mailing list
> GnomeMeeting-list gnome org
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