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newbie: multiple webcams?

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Gerry Deckert

newbie: multiple webcams?

Hi all,

I'm working on a Gstreamer / Python / Gtk project to debut at Burning Man in a few weeks, and I'm hoping to get some suggestions, insight, and pointers to examples. I'm almost completely new to Gstreamer and the Python bindings, but I have gone through the App development manual and the Pygstreamer Tutorial. I'm amazed at the speed and flexibility, and I'm convinced it's the right way to go with my project.
Here's what I'm trying to do: I want to take input from multiple usb webcams (v4lsrcs) at the same time, display video in a window from just one at a time, and have the ability to switch the feed smoothly from camera to camera. Why would I want to do this you ask? So I can set up a ring of cameras and create a bullet-time dance cage, of course. :)
I cobbled together something from various examples that more or less works, but I'm sure there's a better approach. My initial attempt involved detaching and attaching cameras directly to xvimagesink, but this took too long for a smooth transition. In my current setup, each camera is fed through its own videobox, all the videoboxes connect to a single videomixer, and the videomixer goes through ffmpegcolorspace to xvimagesink. All the cameras are running at the same time, and I choose between them by setting the alpha channel on the videobox of the desired camera to 1 while all the others are 0. This results in smooth switching, but I'm sure is not a good use of resources.
So, with that, I have lots of questions. Is there a way to switch between sinks on the videomixer to accomplish the same effect? Is there a fast way to turn the cameras on and off, or should I try turning them on and off in groups? How could I enable recording of the video that's coming out? I'm guessing I want to use a tee element, but how do I enable it on the fly? What about toggling on/off some of the effectv plugins? How could I grab single frames from the cameras? I don't have a good understanding of what's involved in modifying the pipeline on the fly. Is there some documentation or are there some examples anyone could point me to? Suggestions? Any help would be greatly appreciated!

Regards,

Gerry

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Stefan Sauer

Re: newbie: multiple webcams?

hi,

have you tried input-selector from gst-plugin-bad?

Stefan

Gerry Deckert schrieb:

> Hi all,
>
> I'm working on a Gstreamer / Python / Gtk project to debut at Burning Man in a few weeks, and I'm hoping to get some suggestions, insight, and pointers to examples. I'm almost completely new to Gstreamer and the Python bindings, but I have gone through the App development manual and the Pygstreamer Tutorial. I'm amazed at the speed and flexibility, and I'm convinced it's the right way to go with my project.
> Here's what I'm trying to do: I want to take input from multiple usb webcams (v4lsrcs) at the same time, display video in a window from just one at a time, and have the ability to switch the feed smoothly from camera to camera. Why would I want to do this you ask? So I can set up a ring of cameras and create a bullet-time dance cage, of course. :)
> I cobbled together something from various examples that more or less works, but I'm sure there's a better approach. My initial attempt involved detaching and attaching cameras directly to xvimagesink, but this took too long for a smooth transition. In my current setup, each camera is fed through its own videobox, all the videoboxes connect to a single videomixer, and the videomixer goes through ffmpegcolorspace to xvimagesink. All the cameras are running at the same time, and I choose between them by setting the alpha channel on the videobox of the desired camera to 1 while all the others are 0. This results in smooth switching, but I'm sure is not a good use of resources.
> So, with that, I have lots of questions. Is there a way to switch between sinks on the videomixer to accomplish the same effect? Is there a fast way to turn the cameras on and off, or should I try turning them on and off in groups? How could I enable recording of the video that's coming out? I'm guessing I want to use a tee element, but how do I enable it on the fly? What about toggling on/off some of the effectv plugins? How could I grab single frames from the cameras? I don't have a good understanding of what's involved in modifying the pipeline on the fly. Is there some documentation or are there some examples anyone could point me to? Suggestions? Any help would be greatly appreciated!
>
>
> Regards,
>
>
> Gerry
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
> Build the coolest Linux based applications with Moblin SDK & win great prizes
> Grand prize is a trip for two to an Open Source event anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>

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Gerry Deckert

Re: newbie: multiple webcams?

Stefan,

Thanks, I'll give that a try. Missed that one when I was searching for video-related plugins. Any other pointers you could give me?

Cheers,

Gerry

--- On Thu, 8/7/08, Stefan Kost <[hidden email]> wrote:

> From: Stefan Kost <[hidden email]>
> Subject: Re: [gst-devel] newbie: multiple webcams?
> To: "Discussion of the development of GStreamer" <[hidden email]>
> Date: Thursday, August 7, 2008, 1:30 AM
> hi,
>
> have you tried input-selector from gst-plugin-bad?
>
> Stefan
>
> Gerry Deckert schrieb:
> > Hi all,
> >
> > I'm working on a Gstreamer / Python / Gtk
> project to debut at Burning Man in a few weeks, and I'm
> hoping to get some suggestions, insight, and pointers to
> examples. I'm almost completely new to Gstreamer and
> the Python bindings, but I have gone through the App
> development manual and the Pygstreamer Tutorial. I'm
> amazed at the speed and flexibility, and I'm convinced
> it's the right way to go with my project.
> > Here's what I'm trying to do: I want to
> take input from multiple usb webcams (v4lsrcs) at the same
> time, display video in a window from just one at a time, and
> have the ability to switch the feed smoothly from camera to
> camera. Why would I want to do this you ask? So I can set
> up a ring of cameras and create a bullet-time dance cage, of
> course. :)
> > I cobbled together something from various examples
> that more or less works, but I'm sure there's a
> better approach. My initial attempt involved detaching and
> attaching cameras directly to xvimagesink, but this took too
> long for a smooth transition. In my current setup, each
> camera is fed through its own videobox, all the videoboxes
> connect to a single videomixer, and the videomixer goes
> through ffmpegcolorspace to xvimagesink. All the cameras
> are running at the same time, and I choose between them by
> setting the alpha channel on the videobox of the desired
> camera to 1 while all the others are 0. This results in
> smooth switching, but I'm sure is not a good use of
> resources.
> > So, with that, I have lots of questions. Is there
> a way to switch between sinks on the videomixer to
> accomplish the same effect? Is there a fast way to turn the
> cameras on and off, or should I try turning them on and off
> in groups? How could I enable recording of the video
> that's coming out? I'm guessing I want to use a tee
> element, but how do I enable it on the fly? What about
> toggling on/off some of the effectv plugins? How could I
> grab single frames from the cameras? I don't have a
> good understanding of what's involved in modifying the
> pipeline on the fly. Is there some documentation or are
> there some examples anyone could point me to? Suggestions?
> Any help would be greatly appreciated!
> >
> >
> > Regards,
> >
> >
> > Gerry
> >
> >
> -------------------------------------------------------------------------
> > This SF.Net email is sponsored by the Moblin Your Move
> Developer's challenge
> > Build the coolest Linux based applications with Moblin
> SDK & win great prizes
> > Grand prize is a trip for two to an Open Source event
> anywhere in the world
> >
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> > _______________________________________________
> > gstreamer-devel mailing list
> > [hidden email]
> >
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
> >
>
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move
> Developer's challenge
> Build the coolest Linux based applications with Moblin SDK
> & win great prizes
> Grand prize is a trip for two to an Open Source event
> anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel

Stefan Sauer

Re: newbie: multiple webcams?

In reply to this post by Gerry Deckert

Hi,

please keep the list in the loop.

Gerry Deckert schrieb:
> Stefan,
>
> I've just given input-selector a try and ran into trouble. The first camera comes up fine, but when I try to switch cameras (by setting the 'active-pad' property) the video on the next camera is frozen, or stutters through a few frames and then freezes. If I set my pipeline to STATE_NULL, then change the active-pad on the input-selector, then set the pipeline back to STATE_PLAYING it works as expected but there's a 1 second pause while switching, which defeats the purpose.
> Do you have any ideas why this might be the case, or if there is some combination of elements I could put upstream or downstream of the input-selector to improve its behavior? I've tested putting queues on either end, but with no visible difference. Any insight you could provide would be helpful!

I suspect timestamp issues. Can you try this:
v4l2src ! queue leaky=2 ! input-select name=sel ! ,,,
v4l2src ! queue leaky=2 ! sel.
...

Stefan

>
>
> Thanks,
>
>
> Gerry
>
>
>
> --- On Thu, 8/7/08, Stefan Kost <[hidden email]> wrote:
>
>> From: Stefan Kost <[hidden email]>
>> Subject: Re: [gst-devel] newbie: multiple webcams?
>> To: "Discussion of the development of GStreamer" <[hidden email]>
>> Date: Thursday, August 7, 2008, 1:30 AM
>> hi,
>>
>> have you tried input-selector from gst-plugin-bad?
>>
>> Stefan
>>
>> Gerry Deckert schrieb:
>>> Hi all,
>>>
>>> I'm working on a Gstreamer / Python / Gtk
>> project to debut at Burning Man in a few weeks, and I'm
>> hoping to get some suggestions, insight, and pointers to
>> examples. I'm almost completely new to Gstreamer and
>> the Python bindings, but I have gone through the App
>> development manual and the Pygstreamer Tutorial. I'm
>> amazed at the speed and flexibility, and I'm convinced
>> it's the right way to go with my project.
>>> Here's what I'm trying to do: I want to
>> take input from multiple usb webcams (v4lsrcs) at the same
>> time, display video in a window from just one at a time, and
>> have the ability to switch the feed smoothly from camera to
>> camera. Why would I want to do this you ask? So I can set
>> up a ring of cameras and create a bullet-time dance cage, of
>> course. :)
>>> I cobbled together something from various examples
>> that more or less works, but I'm sure there's a
>> better approach. My initial attempt involved detaching and
>> attaching cameras directly to xvimagesink, but this took too
>> long for a smooth transition. In my current setup, each
>> camera is fed through its own videobox, all the videoboxes
>> connect to a single videomixer, and the videomixer goes
>> through ffmpegcolorspace to xvimagesink. All the cameras
>> are running at the same time, and I choose between them by
>> setting the alpha channel on the videobox of the desired
>> camera to 1 while all the others are 0. This results in
>> smooth switching, but I'm sure is not a good use of
>> resources.
>>> So, with that, I have lots of questions. Is there
>> a way to switch between sinks on the videomixer to
>> accomplish the same effect? Is there a fast way to turn the
>> cameras on and off, or should I try turning them on and off
>> in groups? How could I enable recording of the video
>> that's coming out? I'm guessing I want to use a tee
>> element, but how do I enable it on the fly? What about
>> toggling on/off some of the effectv plugins? How could I
>> grab single frames from the cameras? I don't have a
>> good understanding of what's involved in modifying the
>> pipeline on the fly. Is there some documentation or are
>> there some examples anyone could point me to? Suggestions?
>> Any help would be greatly appreciated!
>>>
>>> Regards,
>>>
>>>
>>> Gerry
>>>
>>>
>> -------------------------------------------------------------------------
>>> This SF.Net email is sponsored by the Moblin Your Move
>> Developer's challenge
>>> Build the coolest Linux based applications with Moblin
>> SDK & win great prizes
>>> Grand prize is a trip for two to an Open Source event
>> anywhere in the world
>> http://moblin-contest.org/redirect.php?banner_id=100&url=/
>>> _______________________________________________
>>> gstreamer-devel mailing list
>>> [hidden email]
>>>
>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>>>
>>
>> -------------------------------------------------------------------------
>> This SF.Net email is sponsored by the Moblin Your Move
>> Developer's challenge
>> Build the coolest Linux based applications with Moblin SDK
>> & win great prizes
>> Grand prize is a trip for two to an Open Source event
>> anywhere in the world
>> http://moblin-contest.org/redirect.php?banner_id=100&url=/
>> _______________________________________________
>> gstreamer-devel mailing list
>> [hidden email]
>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel

Gerry Deckert

Re: newbie: multiple webcams?

Stefan,

Thanks for the suggestion. The result is the same, the first camera works fine, there is a pause when I switch to the second, I get a short burst of delayed video, and from then on I get about 1 frame every 10-20 seconds. I've also tried it with leaky=1 just to see, and tried different values for max_size_buffers (2, 0, ...) and the outcome is unchanged. Would a caps filter describing the video stream make a difference, or does that only affect negotiating the links between elements?

Gerry

--- On Sun, 8/10/08, Stefan Kost <[hidden email]> wrote:

> From: Stefan Kost <[hidden email]>
> Subject: Re: [gst-devel] newbie: multiple webcams?
> To: "Gerry Deckert" <[hidden email]>, "Gstreamer" <[hidden email]>
> Date: Sunday, August 10, 2008, 3:29 AM
> Hi,
>
> please keep the list in the loop.
>
> Gerry Deckert schrieb:
> > Stefan,
> >
> > I've just given input-selector a try and ran
> into trouble. The first camera comes up fine, but when I
> try to switch cameras (by setting the 'active-pad'
> property) the video on the next camera is frozen, or
> stutters through a few frames and then freezes. If I set my
> pipeline to STATE_NULL, then change the active-pad on the
> input-selector, then set the pipeline back to STATE_PLAYING
> it works as expected but there's a 1 second pause while
> switching, which defeats the purpose.
> > Do you have any ideas why this might be the case,
> or if there is some combination of elements I could put
> upstream or downstream of the input-selector to improve its
> behavior? I've tested putting queues on either end, but
> with no visible difference. Any insight you could provide
> would be helpful!
>
> I suspect timestamp issues. Can you try this:
> v4l2src ! queue leaky=2 ! input-select name=sel ! ,,,
> v4l2src ! queue leaky=2 ! sel.
> ...
>
> Stefan
>
>
> >
> >
> > Thanks,
> >
> >
> > Gerry
> >
> >
> >
> > --- On Thu, 8/7/08, Stefan Kost
> <[hidden email]> wrote:
> >
> >> From: Stefan Kost <[hidden email]>
> >> Subject: Re: [gst-devel] newbie: multiple webcams?
> >> To: "Discussion of the development of
> GStreamer"
> <[hidden email]>
> >> Date: Thursday, August 7, 2008, 1:30 AM
> >> hi,
> >>
> >> have you tried input-selector from gst-plugin-bad?
> >>
> >> Stefan
> >>
> >> Gerry Deckert schrieb:
> >>> Hi all,
> >>>
> >>> I'm working on a Gstreamer / Python /
> Gtk
> >> project to debut at Burning Man in a few weeks,
> and I'm
> >> hoping to get some suggestions, insight, and
> pointers to
> >> examples. I'm almost completely new to
> Gstreamer and
> >> the Python bindings, but I have gone through the
> App
> >> development manual and the Pygstreamer Tutorial.
> I'm
> >> amazed at the speed and flexibility, and I'm
> convinced
> >> it's the right way to go with my project.
> >>> Here's what I'm trying to do: I
> want to
> >> take input from multiple usb webcams (v4lsrcs) at
> the same
> >> time, display video in a window from just one at a
> time, and
> >> have the ability to switch the feed smoothly from
> camera to
> >> camera. Why would I want to do this you ask? So
> I can set
> >> up a ring of cameras and create a bullet-time
> dance cage, of
> >> course. :)
> >>> I cobbled together something from various
> examples
> >> that more or less works, but I'm sure
> there's a
> >> better approach. My initial attempt involved
> detaching and
> >> attaching cameras directly to xvimagesink, but
> this took too
> >> long for a smooth transition. In my current
> setup, each
> >> camera is fed through its own videobox, all the
> videoboxes
> >> connect to a single videomixer, and the videomixer
> goes
> >> through ffmpegcolorspace to xvimagesink. All the
> cameras
> >> are running at the same time, and I choose between
> them by
> >> setting the alpha channel on the videobox of the
> desired
> >> camera to 1 while all the others are 0. This
> results in
> >> smooth switching, but I'm sure is not a good
> use of
> >> resources.
> >>> So, with that, I have lots of questions.
> Is there
> >> a way to switch between sinks on the videomixer to
> >> accomplish the same effect? Is there a fast way
> to turn the
> >> cameras on and off, or should I try turning them
> on and off
> >> in groups? How could I enable recording of the
> video
> >> that's coming out? I'm guessing I want to
> use a tee
> >> element, but how do I enable it on the fly? What
> about
> >> toggling on/off some of the effectv plugins? How
> could I
> >> grab single frames from the cameras? I don't
> have a
> >> good understanding of what's involved in
> modifying the
> >> pipeline on the fly. Is there some documentation
> or are
> >> there some examples anyone could point me to?
> Suggestions?
> >> Any help would be greatly appreciated!
> >>>
> >>> Regards,
> >>>
> >>>
> >>> Gerry
> >>>
> >>>
> >>
> -------------------------------------------------------------------------
> >>> This SF.Net email is sponsored by the Moblin
> Your Move
> >> Developer's challenge
> >>> Build the coolest Linux based applications
> with Moblin
> >> SDK & win great prizes
> >>> Grand prize is a trip for two to an Open
> Source event
> >> anywhere in the world
> >>
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> >>>
> _______________________________________________
> >>> gstreamer-devel mailing list
> >>> [hidden email]
> >>>
> >>
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
> >>>
> >>
> >>
> -------------------------------------------------------------------------
> >> This SF.Net email is sponsored by the Moblin Your
> Move
> >> Developer's challenge
> >> Build the coolest Linux based applications with
> Moblin SDK
> >> & win great prizes
> >> Grand prize is a trip for two to an Open Source
> event
> >> anywhere in the world
> >>
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> >> _______________________________________________
> >> gstreamer-devel mailing list
> >> [hidden email]
> >>
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel

Gerry Deckert

sample video (was Re: newbie: multiple webcams?)

In reply to this post by Stefan Sauer

FYI, here's a sneak preview of what I'm working on. This shows 16 cameras, switching using the alpha-blending method I mentioned:

http://www.youtube.com/watch?v=3nelr28FSbk

Gerry

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Build the coolest Linux based applications with Moblin SDK & win great prizes
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Stefan Sauer

Re: newbie: multiple webcams?

In reply to this post by Gerry Deckert

hi,

Gerry Deckert schrieb:
> Stefan,
>
> Thanks for the suggestion. The result is the same, the first camera works fine, there is a pause when I switch to the second, I get a short burst of delayed video, and from then on I get about 1 frame every 10-20 seconds. I've also tried it with leaky=1 just to see, and tried different values for max_size_buffers (2, 0, ...) and the outcome is unchanged. Would a caps filter describing the video stream make a difference, or does that only affect negotiating the links between elements?
>
>
if you use videotestsrc instead would it work them. If you could make a
small standalone test app, that uses <n> sources and either videotetsrc
or v4l2src I could try to get another webcam and try with two webcams.
Best would be to file a bug and attach it there.
Also happens if you set sync=FALSE on the sink?

Stefan

> Gerry
>
> --- On Sun, 8/10/08, Stefan Kost <[hidden email]> wrote:
>
>
>> From: Stefan Kost <[hidden email]>
>> Subject: Re: [gst-devel] newbie: multiple webcams?
>> To: "Gerry Deckert" <[hidden email]>, "Gstreamer" <[hidden email]>
>> Date: Sunday, August 10, 2008, 3:29 AM
>> Hi,
>>
>> please keep the list in the loop.
>>
>> Gerry Deckert schrieb:
>>
>>> Stefan,
>>>
>>> I've just given input-selector a try and ran
>>>
>> into trouble. The first camera comes up fine, but when I
>> try to switch cameras (by setting the 'active-pad'
>> property) the video on the next camera is frozen, or
>> stutters through a few frames and then freezes. If I set my
>> pipeline to STATE_NULL, then change the active-pad on the
>> input-selector, then set the pipeline back to STATE_PLAYING
>> it works as expected but there's a 1 second pause while
>> switching, which defeats the purpose.
>>
>>> Do you have any ideas why this might be the case,
>>>
>> or if there is some combination of elements I could put
>> upstream or downstream of the input-selector to improve its
>> behavior? I've tested putting queues on either end, but
>> with no visible difference. Any insight you could provide
>> would be helpful!
>>
>> I suspect timestamp issues. Can you try this:
>> v4l2src ! queue leaky=2 ! input-select name=sel ! ,,,
>> v4l2src ! queue leaky=2 ! sel.
>> ...
>>
>> Stefan
>>
>>
>>
>>> Thanks,
>>>
>>>
>>> Gerry
>>>
>>>
>>>
>>> --- On Thu, 8/7/08, Stefan Kost
>>>
>> <[hidden email]> wrote:
>>
>>>> From: Stefan Kost <[hidden email]>
>>>> Subject: Re: [gst-devel] newbie: multiple webcams?
>>>> To: "Discussion of the development of
>>>>
>> GStreamer"
>> <[hidden email]>
>>
>>>> Date: Thursday, August 7, 2008, 1:30 AM
>>>> hi,
>>>>
>>>> have you tried input-selector from gst-plugin-bad?
>>>>
>>>> Stefan
>>>>
>>>> Gerry Deckert schrieb:
>>>>
>>>>> Hi all,
>>>>>
>>>>> I'm working on a Gstreamer / Python /
>>>>>
>> Gtk
>>
>>>> project to debut at Burning Man in a few weeks,
>>>>
>> and I'm
>>
>>>> hoping to get some suggestions, insight, and
>>>>
>> pointers to
>>
>>>> examples. I'm almost completely new to
>>>>
>> Gstreamer and
>>
>>>> the Python bindings, but I have gone through the
>>>>
>> App
>>
>>>> development manual and the Pygstreamer Tutorial.
>>>>
>> I'm
>>
>>>> amazed at the speed and flexibility, and I'm
>>>>
>> convinced
>>
>>>> it's the right way to go with my project.
>>>>
>>>>> Here's what I'm trying to do: I
>>>>>
>> want to
>>
>>>> take input from multiple usb webcams (v4lsrcs) at
>>>>
>> the same
>>
>>>> time, display video in a window from just one at a
>>>>
>> time, and
>>
>>>> have the ability to switch the feed smoothly from
>>>>
>> camera to
>>
>>>> camera. Why would I want to do this you ask? So
>>>>
>> I can set
>>
>>>> up a ring of cameras and create a bullet-time
>>>>
>> dance cage, of
>>
>>>> course. :)
>>>>
>>>>> I cobbled together something from various
>>>>>
>> examples
>>
>>>> that more or less works, but I'm sure
>>>>
>> there's a
>>
>>>> better approach. My initial attempt involved
>>>>
>> detaching and
>>
>>>> attaching cameras directly to xvimagesink, but
>>>>
>> this took too
>>
>>>> long for a smooth transition. In my current
>>>>
>> setup, each
>>
>>>> camera is fed through its own videobox, all the
>>>>
>> videoboxes
>>
>>>> connect to a single videomixer, and the videomixer
>>>>
>> goes
>>
>>>> through ffmpegcolorspace to xvimagesink. All the
>>>>
>> cameras
>>
>>>> are running at the same time, and I choose between
>>>>
>> them by
>>
>>>> setting the alpha channel on the videobox of the
>>>>
>> desired
>>
>>>> camera to 1 while all the others are 0. This
>>>>
>> results in
>>
>>>> smooth switching, but I'm sure is not a good
>>>>
>> use of
>>
>>>> resources.
>>>>
>>>>> So, with that, I have lots of questions.
>>>>>
>> Is there
>>
>>>> a way to switch between sinks on the videomixer to
>>>> accomplish the same effect? Is there a fast way
>>>>
>> to turn the
>>
>>>> cameras on and off, or should I try turning them
>>>>
>> on and off
>>
>>>> in groups? How could I enable recording of the
>>>>
>> video
>>
>>>> that's coming out? I'm guessing I want to
>>>>
>> use a tee
>>
>>>> element, but how do I enable it on the fly? What
>>>>
>> about
>>
>>>> toggling on/off some of the effectv plugins? How
>>>>
>> could I
>>
>>>> grab single frames from the cameras? I don't
>>>>
>> have a
>>
>>>> good understanding of what's involved in
>>>>
>> modifying the
>>
>>>> pipeline on the fly. Is there some documentation
>>>>
>> or are
>>
>>>> there some examples anyone could point me to?
>>>>
>> Suggestions?
>>
>>>> Any help would be greatly appreciated!
>>>>
>>>>> Regards,
>>>>>
>>>>>
>>>>> Gerry
>>>>>
>>>>>
>>>>>
>> -------------------------------------------------------------------------
>>
>>>>> This SF.Net email is sponsored by the Moblin
>>>>>
>> Your Move
>>
>>>> Developer's challenge
>>>>
>>>>> Build the coolest Linux based applications
>>>>>
>> with Moblin
>>
>>>> SDK & win great prizes
>>>>
>>>>> Grand prize is a trip for two to an Open
>>>>>
>> Source event
>>
>>>> anywhere in the world
>>>>
>>>>
>> http://moblin-contest.org/redirect.php?banner_id=100&url=/
>>
>> _______________________________________________
>>
>>>>> gstreamer-devel mailing list
>>>>> [hidden email]
>>>>>
>>>>>
>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>>
>>>>>
>>>>>
>>>>
>> -------------------------------------------------------------------------
>>
>>>> This SF.Net email is sponsored by the Moblin Your
>>>>
>> Move
>>
>>>> Developer's challenge
>>>> Build the coolest Linux based applications with
>>>>
>> Moblin SDK
>>
>>>> & win great prizes
>>>> Grand prize is a trip for two to an Open Source
>>>>
>> event
>>
>>>> anywhere in the world
>>>>
>>>>
>> http://moblin-contest.org/redirect.php?banner_id=100&url=/
>>
>>>> _______________________________________________
>>>> gstreamer-devel mailing list
>>>> [hidden email]
>>>>
>>>>
>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>>
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
> Build the coolest Linux based applications with Moblin SDK & win great prizes
> Grand prize is a trip for two to an Open Source event anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>

Gerry Deckert

Re: newbie: multiple webcams?

Stefan,

Here's a sample script I put together to test out input-selector using two videotestsrcs as input. I tried many permutations of queues, videorate elements, etc., but this simplified version seems to work the best but still has a slight pause during switching.

Note that I'm using version 0.10.6-5 of plugins-bad, which is all that is available via repositories. Let me know if you think I should go to a source install and upgrade to 0.10.8.

Thanks,

Gerry

--- On Mon, 8/11/08, Stefan Kost <[hidden email]> wrote:

> From: Stefan Kost <[hidden email]>
> Subject: Re: [gst-devel] newbie: multiple webcams?
> To: "Discussion of the development of GStreamer" <[hidden email]>
> Date: Monday, August 11, 2008, 3:51 AM
> hi,
>
> Gerry Deckert schrieb:
> > Stefan,
> >
> > Thanks for the suggestion. The result is the same,
> the first camera works fine, there is a pause when I switch
> to the second, I get a short burst of delayed video, and
> from then on I get about 1 frame every 10-20 seconds.
> I've also tried it with leaky=1 just to see, and tried
> different values for max_size_buffers (2, 0, ...) and the
> outcome is unchanged. Would a caps filter describing the
> video stream make a difference, or does that only affect
> negotiating the links between elements?
> >
> >
> if you use videotestsrc instead would it work them. If you
> could make a
> small standalone test app, that uses <n> sources and
> either videotetsrc
> or v4l2src I could try to get another webcam and try with
> two webcams.
> Best would be to file a bug and attach it there.
> Also happens if you set sync=FALSE on the sink?
>
> Stefan
>
> > Gerry
> >
> > --- On Sun, 8/10/08, Stefan Kost
> <[hidden email]> wrote:
> >
> >
> >> From: Stefan Kost <[hidden email]>
> >> Subject: Re: [gst-devel] newbie: multiple webcams?
> >> To: "Gerry Deckert"
> <[hidden email]>, "Gstreamer"
> <[hidden email]>
> >> Date: Sunday, August 10, 2008, 3:29 AM
> >> Hi,
> >>
> >> please keep the list in the loop.
> >>
> >> Gerry Deckert schrieb:
> >>
> >>> Stefan,
> >>>
> >>> I've just given input-selector a try
> and ran
> >>>
> >> into trouble. The first camera comes up fine, but
> when I
> >> try to switch cameras (by setting the
> 'active-pad'
> >> property) the video on the next camera is frozen,
> or
> >> stutters through a few frames and then freezes.
> If I set my
> >> pipeline to STATE_NULL, then change the active-pad
> on the
> >> input-selector, then set the pipeline back to
> STATE_PLAYING
> >> it works as expected but there's a 1 second
> pause while
> >> switching, which defeats the purpose.
> >>
> >>> Do you have any ideas why this might be the
> case,
> >>>
> >> or if there is some combination of elements I
> could put
> >> upstream or downstream of the input-selector to
> improve its
> >> behavior? I've tested putting queues on
> either end, but
> >> with no visible difference. Any insight you could
> provide
> >> would be helpful!
> >>
> >> I suspect timestamp issues. Can you try this:
> >> v4l2src ! queue leaky=2 ! input-select name=sel !
> ,,,
> >> v4l2src ! queue leaky=2 ! sel.
> >> ...
> >>
> >> Stefan
> >>
> >>
> >>
> >>> Thanks,
> >>>
> >>>
> >>> Gerry
> >>>
> >>>
> >>>
> >>> --- On Thu, 8/7/08, Stefan Kost
> >>>
> >> <[hidden email]> wrote:
> >>
> >>>> From: Stefan Kost
> <[hidden email]>
> >>>> Subject: Re: [gst-devel] newbie: multiple
> webcams?
> >>>> To: "Discussion of the development of
> >>>>
> >> GStreamer"
> >> <[hidden email]>
> >>
> >>>> Date: Thursday, August 7, 2008, 1:30 AM
> >>>> hi,
> >>>>
> >>>> have you tried input-selector from
> gst-plugin-bad?
> >>>>
> >>>> Stefan
> >>>>
> >>>> Gerry Deckert schrieb:
> >>>>
> >>>>> Hi all,
> >>>>>
> >>>>> I'm working on a Gstreamer /
> Python /
> >>>>>
> >> Gtk
> >>
> >>>> project to debut at Burning Man in a few
> weeks,
> >>>>
> >> and I'm
> >>
> >>>> hoping to get some suggestions, insight,
> and
> >>>>
> >> pointers to
> >>
> >>>> examples. I'm almost completely new
> to
> >>>>
> >> Gstreamer and
> >>
> >>>> the Python bindings, but I have gone
> through the
> >>>>
> >> App
> >>
> >>>> development manual and the Pygstreamer
> Tutorial.
> >>>>
> >> I'm
> >>
> >>>> amazed at the speed and flexibility, and
> I'm
> >>>>
> >> convinced
> >>
> >>>> it's the right way to go with my
> project.
> >>>>
> >>>>> Here's what I'm trying to
> do: I
> >>>>>
> >> want to
> >>
> >>>> take input from multiple usb webcams
> (v4lsrcs) at
> >>>>
> >> the same
> >>
> >>>> time, display video in a window from just
> one at a
> >>>>
> >> time, and
> >>
> >>>> have the ability to switch the feed
> smoothly from
> >>>>
> >> camera to
> >>
> >>>> camera. Why would I want to do this you
> ask? So
> >>>>
> >> I can set
> >>
> >>>> up a ring of cameras and create a
> bullet-time
> >>>>
> >> dance cage, of
> >>
> >>>> course. :)
> >>>>
> >>>>> I cobbled together something from
> various
> >>>>>
> >> examples
> >>
> >>>> that more or less works, but I'm sure
> >>>>
> >> there's a
> >>
> >>>> better approach. My initial attempt
> involved
> >>>>
> >> detaching and
> >>
> >>>> attaching cameras directly to xvimagesink,
> but
> >>>>
> >> this took too
> >>
> >>>> long for a smooth transition. In my
> current
> >>>>
> >> setup, each
> >>
> >>>> camera is fed through its own videobox,
> all the
> >>>>
> >> videoboxes
> >>
> >>>> connect to a single videomixer, and the
> videomixer
> >>>>
> >> goes
> >>
> >>>> through ffmpegcolorspace to xvimagesink.
> All the
> >>>>
> >> cameras
> >>
> >>>> are running at the same time, and I choose
> between
> >>>>
> >> them by
> >>
> >>>> setting the alpha channel on the videobox
> of the
> >>>>
> >> desired
> >>
> >>>> camera to 1 while all the others are 0.
> This
> >>>>
> >> results in
> >>
> >>>> smooth switching, but I'm sure is not
> a good
> >>>>
> >> use of
> >>
> >>>> resources.
> >>>>
> >>>>> So, with that, I have lots of
> questions.
> >>>>>
> >> Is there
> >>
> >>>> a way to switch between sinks on the
> videomixer to
> >>>> accomplish the same effect? Is there a
> fast way
> >>>>
> >> to turn the
> >>
> >>>> cameras on and off, or should I try
> turning them
> >>>>
> >> on and off
> >>
> >>>> in groups? How could I enable recording
> of the
> >>>>
> >> video
> >>
> >>>> that's coming out? I'm guessing I
> want to
> >>>>
> >> use a tee
> >>
> >>>> element, but how do I enable it on the
> fly? What
> >>>>
> >> about
> >>
> >>>> toggling on/off some of the effectv
> plugins? How
> >>>>
> >> could I
> >>
> >>>> grab single frames from the cameras? I
> don't
> >>>>
> >> have a
> >>
> >>>> good understanding of what's involved
> in
> >>>>
> >> modifying the
> >>
> >>>> pipeline on the fly. Is there some
> documentation
> >>>>
> >> or are
> >>
> >>>> there some examples anyone could point me
> to?
> >>>>
> >> Suggestions?
> >>
> >>>> Any help would be greatly appreciated!
> >>>>
> >>>>> Regards,
> >>>>>
> >>>>>
> >>>>> Gerry
> >>>>>
> >>>>>
> >>>>>
> >>
> -------------------------------------------------------------------------
> >>
> >>>>> This SF.Net email is sponsored by the
> Moblin
> >>>>>
> >> Your Move
> >>
> >>>> Developer's challenge
> >>>>
> >>>>> Build the coolest Linux based
> applications
> >>>>>
> >> with Moblin
> >>
> >>>> SDK & win great prizes
> >>>>
> >>>>> Grand prize is a trip for two to an
> Open
> >>>>>
> >> Source event
> >>
> >>>> anywhere in the world
> >>>>
> >>>>
> >>
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> >>
> >> _______________________________________________
> >>
> >>>>> gstreamer-devel mailing list
> >>>>> [hidden email]
> >>>>>
> >>>>>
> >>
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
> >>
> >>>>>
> >>>>>
> >>>>
> >>
> -------------------------------------------------------------------------
> >>
> >>>> This SF.Net email is sponsored by the
> Moblin Your
> >>>>
> >> Move
> >>
> >>>> Developer's challenge
> >>>> Build the coolest Linux based applications
> with
> >>>>
> >> Moblin SDK
> >>
> >>>> & win great prizes
> >>>> Grand prize is a trip for two to an Open
> Source
> >>>>
> >> event
> >>
> >>>> anywhere in the world
> >>>>
> >>>>
> >>
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> >>
> >>>>
> _______________________________________________
> >>>> gstreamer-devel mailing list
> >>>> [hidden email]
> >>>>
> >>>>
> >>
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
> >>
> >
> >
> -------------------------------------------------------------------------
> > This SF.Net email is sponsored by the Moblin Your Move
> Developer's challenge
> > Build the coolest Linux based applications with Moblin
> SDK & win great prizes
> > Grand prize is a trip for two to an Open Source event
> anywhere in the world
> >
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> > _______________________________________________
> > gstreamer-devel mailing list
> > [hidden email]
> >
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
> >
>
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move
> Developer's challenge
> Build the coolest Linux based applications with Moblin SDK
> & win great prizes
> Grand prize is a trip for two to an Open Source event
> anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel

test-selector.py (5K) Download Attachment

Gerry Deckert

Re: newbie: multiple webcams?

In reply to this post by Stefan Sauer

Hi all,

Another question for the list. When I try to open too many cameras at once I get this error:

> Error msg from bus: Could not open resource for reading and writing. v4l_calls.c(179): gst_v4l_open (): /player/src1: system error: Cannot allocate memory

Currently I can open 18 cameras simultaneously, but previously I was able to open as many as 29 before seeing this memory error. Why would this be? Are there any properties I can set that would reduce the memory footprint and let me open more?

Here's roughly what my pipeline looks like:

v4lsrc device=/dev/video0 ! ffmpegcolorspace ! video/x-raw-rgb,width=160,height=120 ! videomixer name=mix ! ffmpegcolorspace ! gamme ! xvimagesink
...
v4lsrc device=/dev/video1 ... .mix
...
etc.

I seem to be limited in options for width and height (352x288, 320x240, and 160x120 work), and I don't seem to be able to change the framerate from 25/1 or the depth or bpp from 24. Is that just due to limitations in the v4lsrc element?
I did try setting the v4lsrc 'blocksize' property smaller (from 4096 to 2048), but this didn't seem to make a difference.
Any help would be greatly greatly appreciated. If I can achieve 32 cameras running simultaneously I will be a happy man.

Thanks,

Gerry

--- On Mon, 8/11/08, Stefan Kost <[hidden email]> wrote:

Gerry Deckert

Re: newbie: multiple webcams?

Just a quick addendum, the only major thing that's changed is that I moved from using the motherboard's onboard video to using a dual-head nVidia card with nVidia's X drivers (don't have any model numbers here at the office). Is it plausible that nVidia's drivers are reducing the effective number of cameras I can open at once? I guess I'll attempt disabling the driver or removing the card completely to see what effect that has.

Gerry

--- On Sun, 8/17/08, Gerry Deckert <[hidden email]> wrote:

> From: Gerry Deckert <[hidden email]>
> Subject: Re: [gst-devel] newbie: multiple webcams?
> To: "Discussion of the development of GStreamer" <[hidden email]>
> Date: Sunday, August 17, 2008, 10:33 PM
> Hi all,
>
> Another question for the list. When I try to open too
> many cameras at once I get this error:
>
> > Error msg from bus: Could not open resource for
> reading and writing. v4l_calls.c(179): gst_v4l_open ():
> /player/src1: system error: Cannot allocate memory
>
> Currently I can open 18 cameras simultaneously, but
> previously I was able to open as many as 29 before seeing
> this memory error. Why would this be? Are there any
> properties I can set that would reduce the memory footprint
> and let me open more?
>
> Here's roughly what my pipeline looks like:
>
> v4lsrc device=/dev/video0 ! ffmpegcolorspace !
> video/x-raw-rgb,width=160,height=120 ! videomixer name=mix !
> ffmpegcolorspace ! gamme ! xvimagesink
> ...
> v4lsrc device=/dev/video1 ... .mix
> ...
> etc.
>
> I seem to be limited in options for width and height
> (352x288, 320x240, and 160x120 work), and I don't seem
> to be able to change the framerate from 25/1 or the depth or
> bpp from 24. Is that just due to limitations in the v4lsrc
> element?
> I did try setting the v4lsrc 'blocksize'
> property smaller (from 4096 to 2048), but this didn't
> seem to make a difference.
> Any help would be greatly greatly appreciated. If I can
> achieve 32 cameras running simultaneously I will be a happy
> man.
>
>
> Thanks,
>
>
> Gerry
>
>
>
>
> --- On Mon, 8/11/08, Stefan Kost
> <[hidden email]> wrote:
>
> > From: Stefan Kost <[hidden email]>
> > Subject: Re: [gst-devel] newbie: multiple webcams?
> > To: "Discussion of the development of
> GStreamer"
> <[hidden email]>
> > Date: Monday, August 11, 2008, 3:51 AM
> > hi,
> >
> > Gerry Deckert schrieb:
> > > Stefan,
> > >
> > > Thanks for the suggestion. The result is the
> same,
> > the first camera works fine, there is a pause when I
> switch
> > to the second, I get a short burst of delayed video,
> and
> > from then on I get about 1 frame every 10-20 seconds.
> > I've also tried it with leaky=1 just to see, and
> tried
> > different values for max_size_buffers (2, 0, ...) and
> the
> > outcome is unchanged. Would a caps filter describing
> the
> > video stream make a difference, or does that only
> affect
> > negotiating the links between elements?
> > >
> > >
> > if you use videotestsrc instead would it work them. If
> you
> > could make a
> > small standalone test app, that uses <n> sources
> and
> > either videotetsrc
> > or v4l2src I could try to get another webcam and try
> with
> > two webcams.
> > Best would be to file a bug and attach it there.
> > Also happens if you set sync=FALSE on the sink?
> >
> > Stefan
> >
> > > Gerry
> > >
> > > --- On Sun, 8/10/08, Stefan Kost
> > <[hidden email]> wrote:
> > >
> > >
> > >> From: Stefan Kost
> <[hidden email]>
> > >> Subject: Re: [gst-devel] newbie: multiple
> webcams?
> > >> To: "Gerry Deckert"
> > <[hidden email]>, "Gstreamer"
> > <[hidden email]>
> > >> Date: Sunday, August 10, 2008, 3:29 AM
> > >> Hi,
> > >>
> > >> please keep the list in the loop.
> > >>
> > >> Gerry Deckert schrieb:
> > >>
> > >>> Stefan,
> > >>>
> > >>> I've just given input-selector a
> try
> > and ran
> > >>>
> > >> into trouble. The first camera comes up
> fine, but
> > when I
> > >> try to switch cameras (by setting the
> > 'active-pad'
> > >> property) the video on the next camera is
> frozen,
> > or
> > >> stutters through a few frames and then
> freezes.
> > If I set my
> > >> pipeline to STATE_NULL, then change the
> active-pad
> > on the
> > >> input-selector, then set the pipeline back to
> > STATE_PLAYING
> > >> it works as expected but there's a 1
> second
> > pause while
> > >> switching, which defeats the purpose.
> > >>
> > >>> Do you have any ideas why this might
> be the
> > case,
> > >>>
> > >> or if there is some combination of elements I
> > could put
> > >> upstream or downstream of the input-selector
> to
> > improve its
> > >> behavior? I've tested putting queues on
> > either end, but
> > >> with no visible difference. Any insight you
> could
> > provide
> > >> would be helpful!
> > >>
> > >> I suspect timestamp issues. Can you try this:
> > >> v4l2src ! queue leaky=2 ! input-select
> name=sel !
> > ,,,
> > >> v4l2src ! queue leaky=2 ! sel.
> > >> ...
> > >>
> > >> Stefan
> > >>
> > >>
> > >>
> > >>> Thanks,
> > >>>
> > >>>
> > >>> Gerry
> > >>>
> > >>>
> > >>>
> > >>> --- On Thu, 8/7/08, Stefan Kost
> > >>>
> > >> <[hidden email]> wrote:
> > >>
> > >>>> From: Stefan Kost
> > <[hidden email]>
> > >>>> Subject: Re: [gst-devel] newbie:
> multiple
> > webcams?
> > >>>> To: "Discussion of the
> development of
> > >>>>
> > >> GStreamer"
> > >> <[hidden email]>
> > >>
> > >>>> Date: Thursday, August 7, 2008, 1:30
> AM
> > >>>> hi,
> > >>>>
> > >>>> have you tried input-selector from
> > gst-plugin-bad?
> > >>>>
> > >>>> Stefan
> > >>>>
> > >>>> Gerry Deckert schrieb:
> > >>>>
> > >>>>> Hi all,
> > >>>>>
> > >>>>> I'm working on a Gstreamer
> /
> > Python /
> > >>>>>
> > >> Gtk
> > >>
> > >>>> project to debut at Burning Man in a
> few
> > weeks,
> > >>>>
> > >> and I'm
> > >>
> > >>>> hoping to get some suggestions,
> insight,
> > and
> > >>>>
> > >> pointers to
> > >>
> > >>>> examples. I'm almost completely
> new
> > to
> > >>>>
> > >> Gstreamer and
> > >>
> > >>>> the Python bindings, but I have gone
> > through the
> > >>>>
> > >> App
> > >>
> > >>>> development manual and the
> Pygstreamer
> > Tutorial.
> > >>>>
> > >> I'm
> > >>
> > >>>> amazed at the speed and flexibility,
> and
> > I'm
> > >>>>
> > >> convinced
> > >>
> > >>>> it's the right way to go with my
> > project.
> > >>>>
> > >>>>> Here's what I'm trying
> to
> > do: I
> > >>>>>
> > >> want to
> > >>
> > >>>> take input from multiple usb webcams
> > (v4lsrcs) at
> > >>>>
> > >> the same
> > >>
> > >>>> time, display video in a window from
> just
> > one at a
> > >>>>
> > >> time, and
> > >>
> > >>>> have the ability to switch the feed
> > smoothly from
> > >>>>
> > >> camera to
> > >>
> > >>>> camera. Why would I want to do this
> you
> > ask? So
> > >>>>
> > >> I can set
> > >>
> > >>>> up a ring of cameras and create a
> > bullet-time
> > >>>>
> > >> dance cage, of
> > >>
> > >>>> course. :)
> > >>>>
> > >>>>> I cobbled together something
> from
> > various
> > >>>>>
> > >> examples
> > >>
> > >>>> that more or less works, but I'm
> sure
> > >>>>
> > >> there's a
> > >>
> > >>>> better approach. My initial attempt
> > involved
> > >>>>
> > >> detaching and
> > >>
> > >>>> attaching cameras directly to
> xvimagesink,
> > but
> > >>>>
> > >> this took too
> > >>
> > >>>> long for a smooth transition. In my
> > current
> > >>>>
> > >> setup, each
> > >>
> > >>>> camera is fed through its own
> videobox,
> > all the
> > >>>>
> > >> videoboxes
> > >>
> > >>>> connect to a single videomixer, and
> the
> > videomixer
> > >>>>
> > >> goes
> > >>
> > >>>> through ffmpegcolorspace to
> xvimagesink.
> > All the
> > >>>>
> > >> cameras
> > >>
> > >>>> are running at the same time, and I
> choose
> > between
> > >>>>
> > >> them by
> > >>
> > >>>> setting the alpha channel on the
> videobox
> > of the
> > >>>>
> > >> desired
> > >>
> > >>>> camera to 1 while all the others are
> 0.
> > This
> > >>>>
> > >> results in
> > >>
> > >>>> smooth switching, but I'm sure is
> not
> > a good
> > >>>>
> > >> use of
> > >>
> > >>>> resources.
> > >>>>
> > >>>>> So, with that, I have lots of
> > questions.
> > >>>>>
> > >> Is there
> > >>
> > >>>> a way to switch between sinks on the
> > videomixer to
> > >>>> accomplish the same effect? Is there
> a
> > fast way
> > >>>>
> > >> to turn the
> > >>
> > >>>> cameras on and off, or should I try
> > turning them
> > >>>>
> > >> on and off
> > >>
> > >>>> in groups? How could I enable
> recording
> > of the
> > >>>>
> > >> video
> > >>
> > >>>> that's coming out? I'm
> guessing I
> > want to
> > >>>>
> > >> use a tee
> > >>
> > >>>> element, but how do I enable it on
> the
> > fly? What
> > >>>>
> > >> about
> > >>
> > >>>> toggling on/off some of the effectv
> > plugins? How
> > >>>>
> > >> could I
> > >>
> > >>>> grab single frames from the cameras?
> I
> > don't
> > >>>>
> > >> have a
> > >>
> > >>>> good understanding of what's
> involved
> > in
> > >>>>
> > >> modifying the
> > >>
> > >>>> pipeline on the fly. Is there some
> > documentation
> > >>>>
> > >> or are
> > >>
> > >>>> there some examples anyone could
> point me
> > to?
> > >>>>
> > >> Suggestions?
> > >>
> > >>>> Any help would be greatly
> appreciated!
> > >>>>
> > >>>>> Regards,
> > >>>>>
> > >>>>>
> > >>>>> Gerry
> > >>>>>
> > >>>>>
> > >>>>>
> > >>
> >
> -------------------------------------------------------------------------
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Stefan Sauer

Re: newbie: multiple webcams?

In reply to this post by Gerry Deckert

hi gerry,

Gerry Deckert schrieb:
> Stefan,
>
> Here's a sample script I put together to test out input-selector using two videotestsrcs as input. I tried many permutations of queues, videorate elements, etc., but this simplified version seems to work the best but still has a slight pause during switching.
>
> Note that I'm using version 0.10.6-5 of plugins-bad, which is all that is available via repositories. Let me know if you think I should go to a source install and upgrade to 0.10.8.
>

Trying with cvs version e.g. installed to /usr/local would definitely
nice. I also noticed its v4l, don't you have v4l2 drivers for those cameras?

Stefan

>
> Thanks,
>
>
> Gerry
>
>
> --- On Mon, 8/11/08, Stefan Kost <[hidden email]> wrote:
>
>
>> From: Stefan Kost <[hidden email]>
>> Subject: Re: [gst-devel] newbie: multiple webcams?
>> To: "Discussion of the development of GStreamer" <[hidden email]>
>> Date: Monday, August 11, 2008, 3:51 AM
>> hi,
>>
>> Gerry Deckert schrieb:
>>
>>> Stefan,
>>>
>>> Thanks for the suggestion. The result is the same,
>>>
>> the first camera works fine, there is a pause when I switch
>> to the second, I get a short burst of delayed video, and
>> from then on I get about 1 frame every 10-20 seconds.
>> I've also tried it with leaky=1 just to see, and tried
>> different values for max_size_buffers (2, 0, ...) and the
>> outcome is unchanged. Would a caps filter describing the
>> video stream make a difference, or does that only affect
>> negotiating the links between elements?
>>
>>>
>>>
>> if you use videotestsrc instead would it work them. If you
>> could make a
>> small standalone test app, that uses <n> sources and
>> either videotetsrc
>> or v4l2src I could try to get another webcam and try with
>> two webcams.
>> Best would be to file a bug and attach it there.
>> Also happens if you set sync=FALSE on the sink?
>>
>> Stefan
>>
>>
>>> Gerry
>>>
>>> --- On Sun, 8/10/08, Stefan Kost
>>>
>> <[hidden email]> wrote:
>>
>>>
>>>
>>>> From: Stefan Kost <[hidden email]>
>>>> Subject: Re: [gst-devel] newbie: multiple webcams?
>>>> To: "Gerry Deckert"
>>>>
>> <[hidden email]>, "Gstreamer"
>> <[hidden email]>
>>
>>>> Date: Sunday, August 10, 2008, 3:29 AM
>>>> Hi,
>>>>
>>>> please keep the list in the loop.
>>>>
>>>> Gerry Deckert schrieb:
>>>>
>>>>
>>>>> Stefan,
>>>>>
>>>>> I've just given input-selector a try
>>>>>
>> and ran
>>
>>>>>
>>>>>
>>>> into trouble. The first camera comes up fine, but
>>>>
>> when I
>>
>>>> try to switch cameras (by setting the
>>>>
>> 'active-pad'
>>
>>>> property) the video on the next camera is frozen,
>>>>
>> or
>>
>>>> stutters through a few frames and then freezes.
>>>>
>> If I set my
>>
>>>> pipeline to STATE_NULL, then change the active-pad
>>>>
>> on the
>>
>>>> input-selector, then set the pipeline back to
>>>>
>> STATE_PLAYING
>>
>>>> it works as expected but there's a 1 second
>>>>
>> pause while
>>
>>>> switching, which defeats the purpose.
>>>>
>>>>
>>>>> Do you have any ideas why this might be the
>>>>>
>> case,
>>
>>>>>
>>>>>
>>>> or if there is some combination of elements I
>>>>
>> could put
>>
>>>> upstream or downstream of the input-selector to
>>>>
>> improve its
>>
>>>> behavior? I've tested putting queues on
>>>>
>> either end, but
>>
>>>> with no visible difference. Any insight you could
>>>>
>> provide
>>
>>>> would be helpful!
>>>>
>>>> I suspect timestamp issues. Can you try this:
>>>> v4l2src ! queue leaky=2 ! input-select name=sel !
>>>>
>> ,,,
>>
>>>> v4l2src ! queue leaky=2 ! sel.
>>>> ...
>>>>
>>>> Stefan
>>>>
>>>>
>>>>
>>>>
>>>>> Thanks,
>>>>>
>>>>>
>>>>> Gerry
>>>>>
>>>>>
>>>>>
>>>>> --- On Thu, 8/7/08, Stefan Kost
>>>>>
>>>>>
>>>> <[hidden email]> wrote:
>>>>
>>>>
>>>>>> From: Stefan Kost
>>>>>>
>> <[hidden email]>
>>
>>>>>> Subject: Re: [gst-devel] newbie: multiple
>>>>>>
>> webcams?
>>
>>>>>> To: "Discussion of the development of
>>>>>>
>>>>>>
>>>> GStreamer"
>>>> <[hidden email]>
>>>>
>>>>
>>>>>> Date: Thursday, August 7, 2008, 1:30 AM
>>>>>> hi,
>>>>>>
>>>>>> have you tried input-selector from
>>>>>>
>> gst-plugin-bad?
>>
>>>>>> Stefan
>>>>>>
>>>>>> Gerry Deckert schrieb:
>>>>>>
>>>>>>
>>>>>>> Hi all,
>>>>>>>
>>>>>>> I'm working on a Gstreamer /
>>>>>>>
>> Python /
>>
>>>>>>>
>>>>>>>
>>>> Gtk
>>>>
>>>>
>>>>>> project to debut at Burning Man in a few
>>>>>>
>> weeks,
>>
>>>>>>
>>>>>>
>>>> and I'm
>>>>
>>>>
>>>>>> hoping to get some suggestions, insight,
>>>>>>
>> and
>>
>>>>>>
>>>>>>
>>>> pointers to
>>>>
>>>>
>>>>>> examples. I'm almost completely new
>>>>>>
>> to
>>
>>>>>>
>>>>>>
>>>> Gstreamer and
>>>>
>>>>
>>>>>> the Python bindings, but I have gone
>>>>>>
>> through the
>>
>>>>>>
>>>>>>
>>>> App
>>>>
>>>>
>>>>>> development manual and the Pygstreamer
>>>>>>
>> Tutorial.
>>
>>>>>>
>>>>>>
>>>> I'm
>>>>
>>>>
>>>>>> amazed at the speed and flexibility, and
>>>>>>
>> I'm
>>
>>>>>>
>>>>>>
>>>> convinced
>>>>
>>>>
>>>>>> it's the right way to go with my
>>>>>>
>> project.
>>
>>>>>>
>>>>>>
>>>>>>> Here's what I'm trying to
>>>>>>>
>> do: I
>>
>>>>>>>
>>>>>>>
>>>> want to
>>>>
>>>>
>>>>>> take input from multiple usb webcams
>>>>>>
>> (v4lsrcs) at
>>
>>>>>>
>>>>>>
>>>> the same
>>>>
>>>>
>>>>>> time, display video in a window from just
>>>>>>
>> one at a
>>
>>>>>>
>>>>>>
>>>> time, and
>>>>
>>>>
>>>>>> have the ability to switch the feed
>>>>>>
>> smoothly from
>>
>>>>>>
>>>>>>
>>>> camera to
>>>>
>>>>
>>>>>> camera. Why would I want to do this you
>>>>>>
>> ask? So
>>
>>>>>>
>>>>>>
>>>> I can set
>>>>
>>>>
>>>>>> up a ring of cameras and create a
>>>>>>
>> bullet-time
>>
>>>>>>
>>>>>>
>>>> dance cage, of
>>>>
>>>>
>>>>>> course. :)
>>>>>>
>>>>>>
>>>>>>> I cobbled together something from
>>>>>>>
>> various
>>
>>>>>>>
>>>>>>>
>>>> examples
>>>>
>>>>
>>>>>> that more or less works, but I'm sure
>>>>>>
>>>>>>
>>>> there's a
>>>>
>>>>
>>>>>> better approach. My initial attempt
>>>>>>
>> involved
>>
>>>>>>
>>>>>>
>>>> detaching and
>>>>
>>>>
>>>>>> attaching cameras directly to xvimagesink,
>>>>>>
>> but
>>
>>>>>>
>>>>>>
>>>> this took too
>>>>
>>>>
>>>>>> long for a smooth transition. In my
>>>>>>
>> current
>>
>>>>>>
>>>>>>
>>>> setup, each
>>>>
>>>>
>>>>>> camera is fed through its own videobox,
>>>>>>
>> all the
>>
>>>>>>
>>>>>>
>>>> videoboxes
>>>>
>>>>
>>>>>> connect to a single videomixer, and the
>>>>>>
>> videomixer
>>
>>>>>>
>>>>>>
>>>> goes
>>>>
>>>>
>>>>>> through ffmpegcolorspace to xvimagesink.
>>>>>>
>> All the
>>
>>>>>>
>>>>>>
>>>> cameras
>>>>
>>>>
>>>>>> are running at the same time, and I choose
>>>>>>
>> between
>>
>>>>>>
>>>>>>
>>>> them by
>>>>
>>>>
>>>>>> setting the alpha channel on the videobox
>>>>>>
>> of the
>>
>>>>>>
>>>>>>
>>>> desired
>>>>
>>>>
>>>>>> camera to 1 while all the others are 0.
>>>>>>
>> This
>>
>>>>>>
>>>>>>
>>>> results in
>>>>
>>>>
>>>>>> smooth switching, but I'm sure is not
>>>>>>
>> a good
>>
>>>>>>
>>>>>>
>>>> use of
>>>>
>>>>
>>>>>> resources.
>>>>>>
>>>>>>
>>>>>>> So, with that, I have lots of
>>>>>>>
>> questions.
>>
>>>>>>>
>>>>>>>
>>>> Is there
>>>>
>>>>
>>>>>> a way to switch between sinks on the
>>>>>>
>> videomixer to
>>
>>>>>> accomplish the same effect? Is there a
>>>>>>
>> fast way
>>
>>>>>>
>>>>>>
>>>> to turn the
>>>>
>>>>
>>>>>> cameras on and off, or should I try
>>>>>>
>> turning them
>>
>>>>>>
>>>>>>
>>>> on and off
>>>>
>>>>
>>>>>> in groups? How could I enable recording
>>>>>>
>> of the
>>
>>>>>>
>>>>>>
>>>> video
>>>>
>>>>
>>>>>> that's coming out? I'm guessing I
>>>>>>
>> want to
>>
>>>>>>
>>>>>>
>>>> use a tee
>>>>
>>>>
>>>>>> element, but how do I enable it on the
>>>>>>
>> fly? What
>>
>>>>>>
>>>>>>
>>>> about
>>>>
>>>>
>>>>>> toggling on/off some of the effectv
>>>>>>
>> plugins? How
>>
>>>>>>
>>>>>>
>>>> could I
>>>>
>>>>
>>>>>> grab single frames from the cameras? I
>>>>>>
>> don't
>>
>>>>>>
>>>>>>
>>>> have a
>>>>
>>>>
>>>>>> good understanding of what's involved
>>>>>>
>> in
>>
>>>>>>
>>>>>>
>>>> modifying the
>>>>
>>>>
>>>>>> pipeline on the fly. Is there some
>>>>>>
>> documentation
>>
>>>>>>
>>>>>>
>>>> or are
>>>>
>>>>
>>>>>> there some examples anyone could point me
>>>>>>
>> to?
>>
>>>>>>
>>>>>>
>>>> Suggestions?
>>>>
>>>>
>>>>>> Any help would be greatly appreciated!
>>>>>>
>>>>>>
>>>>>>> Regards,
>>>>>>>
>>>>>>>
>>>>>>> Gerry
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>> -------------------------------------------------------------------------
>>
>>>>
>>>>
>>>>>>> This SF.Net email is sponsored by the
>>>>>>>
>> Moblin
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>>>>>>>
>>>>>>>
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>>>>>> Developer's challenge
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>>>>>>
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>> applications
>>
>>>>>>>
>>>>>>>
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>>>>
>>>>
>>>>>> SDK & win great prizes
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>>>>>>
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>>>>>>>
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>>
>>>>>>>
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>>>>
>>>>
>>>>>> anywhere in the world
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>>>>>>
>>>>>>
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>>>>
>>>> _______________________________________________
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>>>>
>>>>>>>
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>>>>>>
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>>>>>> Developer's challenge
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>>>>>>
>>>>>>
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