[PD] Gem+v4l2loopback (was Re: pdp_vloopback ?)

Antoine Villeret antoine.villeret at gmail.com
Wed Apr 22 16:14:54 CEST 2015


the Iohannes' instructions are still relevant but there are few things you
might pay attention to :
- be sure you belong to "video" group, if you got an error like
"[pix_record] : can't open /dev/video1" this could be the issue (if
/dev/video1 exists of course)
- set and start the capture *before* setting the device capture. The
v4l2device is undefined (nor a capture or a tuner device) until you send
the first frame to it.

here is attached a sample patch that works with current Gem from git.



Le mer. 22 avr. 2015 à 15:06, Mario Mey <mariomey at gmail.com> a écrit :

> Hi, there. I'm reviving a mail from 2011... here it is the last of the
> thread:
> http://lists.puredata.info/pipermail/pd-list/2011-02/086741.html
> I was looking for help to use Gem with v4l2loopback.
> These mails are the only ones where I found the way to do
> it (no other place in internet).
> After installing v4l2loopback kernel module, I did what IOhannes said:
> ------------
> you should be able to use [pix_record] with v4l2loopback.
> just do:
> - - create [pix_record]
> - - check at the console whether it prints something like "[pix_record]:
> backend #1='V4L2'" (this will only happen the first time you create a
> [pix_record] object for hygienic reasons)
> - - if so, continue
> - - set the codec to "v4l2" and the output filename to /dev/video1 (or
> whatever your loopback-device is).
> something like [codec v4l2, filename /dev/video1, record 1( should do
> the trick.
> f
> gmasdr
> IOhannes
> -----------
> Now, there is /dev/video1 (also, /dev/video0 from Webcam). But, when
> I try to open that device with VLC, I got this error:
> [0x7fed08000e28] v4l2 demux error: not a video capture device
> [0x7fed08000e28] v4l2 demux error: not a radio tuner device
> [0x7fed08000e08] v4l2 access error: not a video capture device
> [0x7fed18003898] main input error: open of `v4l2:///dev/video1' failed
> I tried to open with Blender, videoOnTexture, but the texture
> is black. There's no error messages.
> What am I doing wrong?
> I have Pd-extended 0.44.0-extended-20130808, Ubuntu 14.04.
> I don't know how to know Gem version.
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