gst_parse_launch from /dev/video*

[meuchel]

Hi all,

I'm using GStreamer Core Library version 0.10.36 with ubuntu 14.04
I have a web cam as video source and when I call gst-launch as below the
stream will be displayed:
$ gst-launch v4l2src device=/dev/video0 !
'video/x-raw-yuv,width=640,height=480,framerate=30/1' ! xvimagesink

Now I would like to know how to manage streaming from /dev/video* source
from a C-program (with gst_parse_launch?) and not via gst-launch.
Any hint?

I tried to modify basic-tutorial-1.c in different ways e.g.:
pipeline = gst_parse_launch ("v4l2src device=/dev/video0 !
'video/x-raw-yuv,width=640,height=480,framerate=30/1' ! xvimagesink", NULL);
  
and got this:

$ ./basic-tutorial-1
(basic-tutorial-1:11641): GStreamer-CRITICAL **: gst_element_set_state:
assertion `GST_IS_ELEMENT (element)' failed
(basic-tutorial-1:11641): GStreamer-CRITICAL **: gst_element_get_bus:
assertion `GST_IS_ELEMENT (element)' failed
(basic-tutorial-1:11641): GStreamer-CRITICAL **: gst_bus_timed_pop_filtered:
assertion `GST_IS_BUS (bus)' failed
(basic-tutorial-1:11641): GStreamer-CRITICAL **: gst_object_unref: assertion
`object != NULL' failed
(basic-tutorial-1:11641): GStreamer-CRITICAL **: gst_element_set_state:
assertion `GST_IS_ELEMENT (element)' failed
(basic-tutorial-1:11641): GStreamer-CRITICAL **: gst_object_unref: assertion
`object != NULL' failed

I also tried different other syntaxes for gst_parse_launch but with no
success.
I'm very new regarding Gstreaming and any help would be fine.



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