[PD] Gem+v4l2loopback

IOhannes m zmölnig zmoelnig at iem.at
Thu Apr 23 21:21:30 CEST 2015

On 04/23/2015 09:02 PM, Mario Mey wrote:
> El 23/04/15 a las 12:14, IOhannes m zmoelnig escibió:
>> On 2015-04-23 15:51, Mario Mey wrote:
>>> Well, I don't know if I was on 'video' group but I did the addition.  I
>>> checked the file you sent me and it works. However, for the moment, I
>>> have 3 questions:
>>> - If I don't activate the device in the right side of the patch, nor
>>> Blender nor VLC can get the image from /dev/video1 (VLC shows errors on
>>> console, Blender says nothing, but it makes black texture) Why is like
>>> that? Supposedly, being pix_record there and activated, I should get
>>> from where I want...
>> this could have a multitude of reasons.
>> i would suggest first checking what those errors are that VLC throws
>> (chances are they mean something).
>> then try using gstreamer(-0.10!) to display the video. something like:
>>    $ gst-launch0.10 v4l2src device=/dev/video1 ! ffmpegcolorspace !
>> xvimagesink
> After some tests (including using gst-launch0.10)... I realized that I
> was wrong. Blender and VLC can read from /dev/video1 without activating
> it on Pd.

unfortunately i don't know what you mean exactly with "activating".

> But... I need to create gemwin before VLC or Blender or Gstreamer. Is
> this normal? Should I need gem window opened? It is for gemhead to make
> gemlists... isn't it?

and you need gemlists for pix sources to emit pixel data.
and you need pixel data for [pix_record] to set the output frame
and you need to set the output frame dimensions/colorspace in order to
turn a v4l2loopback OUTPUT device into a CAPTURE device.
and you need a CAPTURE device in order to read it in blender, vlc,... or
any other capturing application.

>> anyhow, this means that the v4l2loopback output is working.
>> so that leaves two more potential candidates for your*problem*:
> Do you mean the Blender and VLC getting "problem"? It is resolved.
> Well... maybe it never was there.
>> - the v4l2loopback kernel module (there are some known issues with e.g.
>> gstreamer-1.0; which version are you using?)

> I didn't know I had gstreamer installed on the system. I have 1.0 and 0.10.

i was referring to the version of v4l2loopback.
sorry for the confusion.


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