Introduction into GStreamer, how it is actually nothing like the title

1. GStreamer
Black Magic and Witchcraft
--what it is not--
Marc Leeman
Barco Networking Division

2. Content
● Goal
● Introduction
● Common misconceptions
● Fun and Games
● Development

3. Goal
● The presentation should allow the audience to
leave the room and start playing with it
○ No fancy products
○ No hocus-pocus with hardware acceleration
○ No real-life examples
○ Really, nothing useful...

4. Introduction
● What is GStreamer
○ set of libraries with a couple of example
programs
○ highly configurable
○ streaming framework, modular
■ autoplugging
■ dynamic loading
■ caps, incremental buildup pipeline,
visualisation of procedure, ...

5. Common misconceptions
● GStreamer is slow
○ Pretty harmless: educate them
○ Performance issues are mostly due to bugs (e.g.
alsa, h.264 parsing, …)
● GStreamer is not for embedded
○ Stuck in the previous century?
○ Axis encoders, cell phones, Settop boxes, ...

6. Basic Tools
● What GStreamer instance do I have?
○ (jhbuild)marc@drd1812:~$ gst-inspect-1.0 |grep barco
○ barcortp: rtpsink: RtpSink
○ barcortp: rtpsrc: rtpsrc
○ barco: edgeblend: EdgeBlend
○ barco: vbcpsrc: VBCP client source
○ (jhbuild)marc@drd1812:~$ gst-inspect-1.0 rtpsink
○ Factory Details:
○ Rank: none (0)
○ Long-name: RtpSink
○ Klass: Generic/Bin/Sink
○ Description: Barco Rtp sink
○ Author: Thijs Vermeir <thijs.vermeir@barco.com>, Marc Leeman <marc.leeman@barco.com>, Paul Henrys
<visechelle@gmail.com>
○
○ Plugin Details:
○ Name: barcortp
○ Description: Barco RTP Plugins
○ Filename: /home/marc/gstreamer.jhbuild/build/lib/gstreamer-1.0/libgst-plugins-barcortp.so
○ Version: 1.0.0.11.1
○ License: LGPL
○ Source module: gst-plugins-barcortp
○ Binary package: Barco
○ Origin URL: http://www.barco.com/
….
● Experiment with gst-launch

7. Fun and Games
● Get a copy of GStreamer 1.x
○ apt-get install …
○ make menuconfig && make (hardcore)
● Here we go…
● Capture from the V4L2 interface, and show
○ $ gst-launch-1.0 v4l2src ! videoconvert ! xvimagesink
● Scale the video
○ $ gst-launch-1.0 v4l2src ! videoscale ! video/x-raw, width=640, height=360 ! videoconvert !
xvimagesink
● Do both
○ gst-launch-1.0 v4l2src ! tee name=t t. ! queue ! videoscale ! video/x-raw, width=640, height=360 !
videoconvert ! xvimagesink t. ! queue ! videoconvert ! videoflip method=2 ! xvimagesink

8. Fun and Games
● What is happening here?
○ gst-launch-1.0 v4l2src ! tee name=t t. ! queue ! videoscale ! video/x-raw, width=640, height=360 !
videoconvert ! xvimagesink t. ! queue ! videoconvert ! videoflip method=2 ! videocrop left=400
right=400 ! xvimagesink
● Capture red colour, live
○ gst-launch-1.0 v4l2src ! tee name=t t. ! queue ! videoscale ! video/x-raw, width=640, height=360 !
videoconvert ! xvimagesink t. ! queue ! videoflip method=2 ! videocrop left=400 right=400 ! alpha
method=custom target-r=245 target-g=0 ! videoconvert ! xvimagesink
● Use camera and overlay “snow in a box”
○ gst-launch-1.0 videomixer name=mixer sink_1::alpha=0.5 sink_1::xpos=50 sink_1::ypos=50 ! video/x-
raw,width=1280,height=720 ! videoconvert ! ximagesink sync=0 videotestsrc pattern=snow
timestamp-offset=3000000000 ! "video/x-raw,format=AYUV,width=640,height=480,framerate=
(fraction)30/1" ! timeoverlay ! queue2 ! mixer. v4l2src ! timeoverlay ! queue2 ! videoconvert ! mixer.

9. Fun and Games
● What about other formats?
○ gst-launch-1.0 videomixer name=mixer sink_1::alpha=0.5 sink_1::xpos=50 sink_1::ypos=50 ! video/x-raw,
width=1280,height=720 ! videoconvert ! fpsdisplaysink sync=0 videotestsrc timestamp-
offset=3000000000 horizontal-speed=1 ! "video/x-raw,format=AYUV,width=640,height=480,
framerate=(fraction)30/1" ! timeoverlay ! queue2 ! mixer. v4l2src ! timeoverlay ! queue2 !
videoconvert ! mixer.
● Something more nerdy?
○ gst-launch-1.0 videomixer name=mixer sink_1::alpha=0.5 sink_1::xpos=50 sink_1::ypos=50 ! video/x-raw,
width=1280,height=720 ! videoconvert ! fpsdisplaysink sync=0 filesrc
location=/home/marc/battlestar.galactica.blood.and.chrome.2012.1080p.bluray.x264-geckos.mkv !
decodebin ! videoconvert ! videoscale ! "video/x-raw,format=AYUV,width=640,height=480" !
timeoverlay ! queue2 ! mixer. v4l2src ! timeoverlay ! queue2 ! videoconvert ! mixer.
● More work
○ gst-launch-1.0 videomixer name=mixer sink_1::alpha=0.5 sink_1::xpos=50 sink_1::ypos=50 ! video/x-raw,
width=1280,height=720 ! videoconvert ! fpsdisplaysink sync=0 filesrc
location=/home/marc/battlestar.galactica.blood.and.chrome.2012.1080p.bluray.x264-geckos.mkv !
decodebin ! videoconvert ! videoscale ! "video/x-raw,format=AYUV,width=640,height=360" !
timeoverlay ! queue2 ! mixer. v4l2src ! timeoverlay ! queue2 ! videoconvert ! mixer.

10. Development
● Develop against git master
○ lots-a-fixes, lots-a-features
○ cooperation on IRC
○ avoid fixing something that was fixed
○ jhbuild (cerbero): standalone development
environment, free from system configuration
○ 0.10 is dead, long live 1.0
● Runs on lots-a OSes (Linux, OSX, Windows) on
lots-a architectures
○ Active development is mostly done in Linux
○ There is hardware impact