[gst-devel] newbie: multiple webcams?
Gerry Deckert
gerry_deckert at yahoo.com
Mon Aug 18 07:33:26 CEST 2008
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 <ensonic at hora-obscura.de> wrote:
> From: Stefan Kost <ensonic at hora-obscura.de>
> Subject: Re: [gst-devel] newbie: multiple webcams?
> To: "Discussion of the development of GStreamer" <gstreamer-devel at lists.sourceforge.net>
> 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
> <ensonic at hora-obscura.de> wrote:
> >
> >
> >> From: Stefan Kost <ensonic at hora-obscura.de>
> >> Subject: Re: [gst-devel] newbie: multiple webcams?
> >> To: "Gerry Deckert"
> <gerry_deckert at yahoo.com>, "Gstreamer"
> <gstreamer-devel at lists.sourceforge.net>
> >> 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
> >>>
> >> <ensonic at hora-obscura.de> wrote:
> >>
> >>>> From: Stefan Kost
> <ensonic at hora-obscura.de>
> >>>> Subject: Re: [gst-devel] newbie: multiple
> webcams?
> >>>> To: "Discussion of the development of
> >>>>
> >> GStreamer"
> >> <gstreamer-devel at lists.sourceforge.net>
> >>
> >>>> 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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