It takes about 5 min, and after 3 or 4 times paying attention, seems always about 5 min.

gdb --args \
  gst-launch-1.0 \
            decklinkvideosrc mode=18 connection=2 ! \
		videoconvert ! \
                videorate ! \
                videoscale ! \
            video/x-raw,format=I420,width=1280,height=720,framerate=30000/1001,pixel-aspect-ratio=1/1 ! \
mux. \
            decklinkaudiosrc ! \
            audio/x-raw,format=S16LE,channels=2,layout=interleaved,rate=48000 ! \
     mux. \
            matroskamux name=mux ! \
                 tcpclientsink host=127.0.0.1 port=10000 \

juser@cnt3:~$ ./g.sh 
GNU gdb (Ubuntu 7.11-0ubuntu1) 7.11
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
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<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from gst-launch-1.0...Reading symbols from /usr/lib/debug/.build-id/7f/218224d9efb937a9b838739ff5134d786f27c6.debug...done.
done.
(gdb) run
Starting program: /usr/bin/gst-launch-1.0 decklinkvideosrc mode=18 connection=2 \! videoconvert \! videorate \! videoscale \! video/x-raw,format=I420,width=1280,height=720,framerate=30000/1001,pixel-aspect-ratio=1/1 \! mux. decklinkaudiosrc \! audio/x-raw,format=S16LE,channels=2,layout=interleaved,rate=48000 \! mux. matroskamux name=mux \! tcpclientsink host=127.0.0.1 port=10000
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Setting pipeline to PAUSED ...
[New Thread 0x7ffff019c700 (LWP 19542)]
[New Thread 0x7fffef99b700 (LWP 19543)]
[New Thread 0x7fffef19a700 (LWP 19544)]
Pipeline is live and does not need PREROLL ...
[New Thread 0x7fffee999700 (LWP 19545)]
Setting pipeline to PLAYING ...
New clock: GstDecklinkInputClock
[New Thread 0x7fffee198700 (LWP 19546)]
[New Thread 0x7fffd74b8700 (LWP 19547)]
[Thread 0x7fffd74b8700 (LWP 19547) exited]

Thread 6 "decklinkvideosr" received signal SIGSEGV, Segmentation fault.

+ Trace 236229