Multiple H264 cameras to MKV (GST1.1.2)

[Robert Krakora]

Hi Adam,

I echo Tim's comments...plus, there are a lot of unneeded memory copies
occurring in v4l2src which pushes up CPU consumption (30->40% CPU usage per
C920 v4l2src instance).  I hacked the v4l2src code and was able to get the
CPU consumption down to the levels of GStreamer 0.10 v4l2src at about
8->15% CPU usage.  I think that there is work being done to rectify this.

Best Regards,

Rob Krakora



On Sun, Sep 8, 2013 at 2:17 PM, Tim-Philipp Müller <t.i.m at zen.co.uk> wrote:

> On Sun, 2013-09-08 at 21:24 +1200, Adam Goodwin wrote:
>
> Hi Adam,
>
> > I have a pipeline in a C application which I've noticed doesn't work
> > smoothly with more than one camera.
> >
> >
> > Currently I'm using two Logitech C920 cameras (with hardware H264
> > encoding) in a pipeline which has these branches from the two cameras:
> >
> >
> > v4l2src--->queue--->capsfilter--->h264parse--->tee--->
> >
> >
> > v4l2src--->queue--->capsfilter--->h264parse--->tee--->
> >
> >
> > After the tees, there are these two branches:
> >
> >
> > --->queue--->rtph264pay--->udpsink
> >
> >
> >
> > --->matroskamux--->queue--->filesink
> >
> >
> > Each tee feeds into the matroskamux branch, which creates a file with
> > (in this case) two video streams. Only one of the tees is linked to
> > the network streaming branch at a time (the user can switch the linked
> > tee when the application runs).
> >
> >
> > What I notice is that the program runs fine, and terminates fine when
> > the user forces an EOS, but the received video (from over the network,
> > currently just to 127.0.0.1) has quite a lot of artifacts.
> >
> > When I open the resulting MKV file (with VLC) the two video streams
> > are displayed. However, there are similar artifacts to those seen when
> > displaying the video live from UDP/RTP. The video also hangs for a few
> > frames periodically, maybe once every couple of seconds. Finally, the
> > timing is also wrong for the MKV.
> >
> > For example, in a 47 second video, VLC kept track of the current time
> > correctly up until 8 seconds in. Then the time displayed by VLC got
> > stuck at 48 seconds(!) while the progress bar for the video continued
> > to show the correct stream position right up until the video ended
> > after 47 seconds.
> >
> >
> > None of these problems happen with either the RTP stream or the MKV
> > file when only one camera is connected and used. (Well, the MKV
> > playback getting stuck on the same frame every few seconds still
> > happens, but that's the least of my problems).
> >
> >
> > Does anyone have any ideas what could be wrong? I thought it could be
> > something to do with not having enough threads, which I've read can be
> > a problem with a branching pipeline, but each branch has a queue
> > element so I don't know what else to do.
>
> Maybe it's related to
>
> https://bugzilla.gnome.org/show_bug.cgi?id=706083
>
> only that running it with two cameras increases the chances of it
> happening?
>
> Cheers
>  -Tim
>
>
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>



-- 

Rob Krakora,
Senior Software Engineer

MessageNet Systems
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Carmel, IN 46032

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