Replacement for vloopback?

Replacement for vloopback?

[Neuer User]

Hello

I need to have access to my webcam from two applications (one is
"motion", the other a video sip phone).

I have googled a lot, but only found vloopback as a method to access a
video device from two applications. However, vloopback seems to rely on
V4L1 which is mostly no longer compiled into the kernel by most distros.
Additionally, it does not seem to compile against newer kernels.

So, my question ist: Is vloopback the right way to go for this
requirement? If yes, how to get it working?

If not, what can I use to have two apps accessing the video stream from
the webcam?

Thanks a lot for any help

Michael

Re: Replacement for vloopback?

[Rémi Denis-Courmont]

On Wed, 06 Feb 2013 14:57:43 +0100, Neuer User <auslands-kv@gmx.de> wrote:

> So, my question ist: Is vloopback the right way to go for this

> requirement? If yes, how to get it working?



No. Video loopback is just a way for an application to expose a virtual

camera, for another application to use. It is not a way to share a camera

within two applications.



Sharing a camera is fundamentally impossible due to the limitation of the

hardware, which cannot capture in two different formats and sets of buffers

simultaneously. Live with it.



-- 

Rémi Denis-Courmont

Sent from my collocated server

Re: Replacement for vloopback?

[Neuer User]

Thanks for answering.

The vloopback description seems to imply that it is possible to share a
camera stream:

"How to use multiple webcam applications with vloopback

[...]
Do "modprobe vloopback pipes=2". Then "resize /dev/video0 /dev/video1
640x480 640x480 & resize /dev/video2 /dev/video3 640x480 320x240".
(Assuming that you have only one real video device at /dev/video0. You
can check with dmesg).

Now, you can watch your webcam with camstream at 640x480 (choose the
device called vloopback0 output in camstream's menu, which is
/dev/video2), at the sime time you can record a video of your webcam
stream at 320x240 by doing "ffmpeg -vd /dev/video4 -s 320x240
picture.mpeg", you can at the same time run a webcam http server by
running "camsource" (after editting camsource.conf to choose /dev/video2
or /dev/video4 as v4l_input source)."

If it is not possible to have two applications access the same video
stream, that is pretty detrimentical to quite a lot of use cases, e.g.:

a.) Use motion to detect motion and record video. At the same time view
the camera output on the screen.

b.) Stream a webcam output over the net and at the same time view it on
the screen.


Actually, for me it would be no problem, if the stream needs to be the
same format etc.

So, really no way? :-(

Thanks

Michael



> On Wed, 06 Feb 2013 14:57:43 +0100, Neuer User <auslands-kv@gmx.de> wrote:
>> So, my question ist: Is vloopback the right way to go for this
>> requirement? If yes, how to get it working?
> 
> No. Video loopback is just a way for an application to expose a virtual
> camera, for another application to use. It is not a way to share a camera
> within two applications.
> 
> Sharing a camera is fundamentally impossible due to the limitation of the
> hardware, which cannot capture in two different formats and sets of buffers
> simultaneously. Live with it.
> 
> -- Rémi Denis-Courmont Sent from my collocated server 

Re: Replacement for vloopback?

[Devin Heitmueller]

On Wed, Feb 6, 2013 at 9:42 AM, Neuer User <auslands-kv@gmx.de> wrote:
> If it is not possible to have two applications access the same video
> stream, that is pretty detrimentical to quite a lot of use cases, e.g.:
>
> a.) Use motion to detect motion and record video. At the same time view
> the camera output on the screen.
>
> b.) Stream a webcam output over the net and at the same time view it on
> the screen.

FWIW:  usually when people ask for this sort of functionality
(performing multiple functions on the same stream), they will
typically use frameworks like gstreamer, which allow for creation of
pipelines to perform the sorts of use cases you have described.

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com

Re: Replacement for vloopback?

[Neuer User]

Well, I have a (what I think) pretty simple use case here, but without
any gstreamer involved:

I have a software video sip phone (based on pjsip). I would like to
automatically initiate a video call when there is a certain amount of
motion detected.

Both software packages access a v4l device. I have no idea how to change
that to a gstreamer pipe. Ma guess is that it will probably be very
difficult :-(

Michael

Am 06.02.2013 15:51, schrieb Devin Heitmueller:
> On Wed, Feb 6, 2013 at 9:42 AM, Neuer User <auslands-kv@gmx.de> wrote:
>> If it is not possible to have two applications access the same video
>> stream, that is pretty detrimentical to quite a lot of use cases, e.g.:
>>
>> a.) Use motion to detect motion and record video. At the same time view
>> the camera output on the screen.
>>
>> b.) Stream a webcam output over the net and at the same time view it on
>> the screen.
> 
> FWIW:  usually when people ask for this sort of functionality
> (performing multiple functions on the same stream), they will
> typically use frameworks like gstreamer, which allow for creation of
> pipelines to perform the sorts of use cases you have described.
> 
> Devin
> 

Re: Replacement for vloopback?

[Neuer User]

Thanks everybody so far.

I just found v4l2loopback and also some examples with gestreamer.

I will do some testing and see if I can get my use case done with that.

Kind regards

Michael

Am 06.02.2013 14:57, schrieb Neuer User:
> Hello
> 
> I need to have access to my webcam from two applications (one is
> "motion", the other a video sip phone).
> 
> I have googled a lot, but only found vloopback as a method to access a
> video device from two applications. However, vloopback seems to rely on
> V4L1 which is mostly no longer compiled into the kernel by most distros.
> Additionally, it does not seem to compile against newer kernels.
> 
> So, my question ist: Is vloopback the right way to go for this
> requirement? If yes, how to get it working?
> 
> If not, what can I use to have two apps accessing the video stream from
> the webcam?
> 
> Thanks a lot for any help
> 
> Michael
>