uvch264src: Only broken examples

Alexandru Csete oz9aec at gmail.com
Sun Feb 23 01:37:59 PST 2014

Hi Mark,

I don't know what to say besides confirming that my examples work for me
using gstreamer 1.2.2. Perhaps there are some clues of an error in the
"bunch of stuff" that you get in the terminal. Perhaps something goes wrong
while you copy & paste the long command.

Anyway, it sounds like you are using gstreamer out of necessity and not
because you want to. Gstreamer is a development framework and not an
end-user application. It is intended for application developers. If you
just want to use your webcam you should use an application intended for
that. Theoretically, all webcam applications should work with the C920 but
in practice probably not all of them support H.264 stream. I know qv4l2 and
guvcview support H.264 streams and work with the C920 and C930, though I
haven't tried for quite a while.

The double-speed playback could be a firmware bug.


On Sun, Feb 23, 2014 at 5:28 AM, Mark Scudder <mark at markscudder.com> wrote:

> Hello. New gstreamer user. Latest version compiled from source on a new
> Linux Mint 16 install.
> All I'm trying to do at the moment is save video and audio to disk from a
> Logitech c920. Nothing fancy, just what the bundled Windows app would do.
> I'll get fancy with it later. However, I can only find examples that don't
> work.
> Here's one, for instance, in fact the only reasonably close documentation
> I can find on how to even get started:
> http://oz9aec.net/index.php/gstreamer/487-using-the-logitech-c920-webcam-with-gstreamer-12
> I have a c920, I'm using gstreamer 1.2, so far so good. I paste the first
> example into a terminal. It says I should get two windows on screen, the
> low res viewfinder and a high quality 720p image as well.
> When I run this pipeline only the small window appears, showing me one
> frozen frame, but no video. A bunch of stuff comes up in the terminal
> window, but no errors.
> When I try to run the second example the same thing happens.
> The v4l2src example works, but if I change xvimagesink to filesink
> (ignoring for the moment that I don't have a viewfinder), the recorded
> video plays back at double speed.
> I guess I have two questions; first, somebody has to have made this work
> with the uvch264src plugin, otherwise why write it? And secondly, if the
> syntax of gstreamer has to be so complex, why have I not found more than a
> few examples out there of pipelines that actually work? Where's the
> definitive, rock-solid, working solution to saving the h264 stream from the
> c920 to disk? I feel like the driver should do it without me having to
> learn the magic words. If the driver is designed to take h264 video off a
> camera and send it to an imagesink or filesink, shouldn't it do that by
> default?
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