GStreamer
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GStreamer 101
Examples
v4l2src can always be replaced by videotestsrc, and alsasrc by audiotestsrc.
Beginning of a normal video pipeline:
v4l2src ! queue ! videorate ! video/x-raw-yuv,framerate=15/1 ! videoscale ! video/x-raw-yuv,width=160,height=120 ! ...
Beginning of a normal audio pipeline:
alsasrc ! audio/x-raw-int,rate=8000,channels=1,depth=8 ! ...
Video encoding:
... ! ffmpegcolorspace ! theoraenc ! ...
Audio encoding:
... ! audioconvert ! vorbisenc ! ...
Video output:
... ! ffmpegcolorspace ! videoscale ! ximagesink
Audio output:
... ! audioconvert ! alsasink sync=false
Stdout:
... ! fdsink fd=1
Encode video+audio as ogg:
v4l2src ! queue ! ffmpegcolorspace ! theoraenc ! queue ! \ oggmux name=mux alsasrc ! queue ! audioconvert ! vorbisenc ! queue ! mux. mux. ! queue ! ...
A long version of videotestsrc ! ximagesink:
videotestsrc ! theoraenc ! oggmux ! oggdemux ! theoradec ! ffmpegcolorspace ! videoscale ! ximagesink
A long version of videotestsrc ! ximagesink &; audiotestsrc ! alsasink:
videotestsrc ! ffmpegcolorspace ! theoraenc ! queue ! \
oggmux name=mux audiotestsrc ! audioconvert ! vorbisenc ! queue ! mux. mux. ! queue ! \
oggdemux name=demux ! queue ! theoradec ! ffmpegcolorspace ! \
ximagesink demux. ! queue ! vorbisdec ! audioconvert ! alsasink
- Hangs on current fc6. MitchellNCharity 17:43, 12 June 2007 (EDT)
Live video streaming to an icecast server:
v4l2src ! ffmpegcolorspace ! videoscale ! video/x-raw-yuv,width=320,height=240 ! theoraenc quality=16 ! oggmux ! shout2send ip=192.168.1.100 port=8000 password=hackme mount=olpc.ogg
Live streaming to an icecast server:
v4l2src ! queue ! ffmpegcolorspace ! theoraenc quality=16 ! queue ! oggmux name=mux alsasrc ! audio/x-raw-int,rate=8000,channels=1,depth=8 ! queue ! audioconvert ! vorbisenc ! queue ! mux. mux. ! \ queue ! shout2send ip=... port=... password=... mount=/whatever.ogg
Notes
video size, framerate, and theoraenc quality
audio encoding
glive.py used wav rather than vorbis. Why?
Elements
Adapters:
- tee
- queue
- videoscale Convert video size.
- videorate Convert video rate.
- ffmpegcolorspace Convert video colorspace.
- audioconvert Convert audio format.
Video characteristics:
Audio characteristics:
File I/O:
Video sources:
- videotestsrc
v4l2srcbroken
Audio sources:
Coding video:
Coding audio:
Wrapping:
oggmuxbroken (MitchellNCharity 11:44, 13 June 2007 (EDT))- oggdemux
Outputing video:
Outputting audio:
Not sure about:
Sending ogg to an icecast streaming server:
... ! shout2send ip=... port=... password=... mount=/whatever.ogg gst-launch ... ! fdsink | oggfwd host port password mount
- Regretabbly, it appears fc6, and thus olpc, does not include shout2send in gst-plugins-good-plugins. Nor does it have rpms for oggfwd, or other possible alternatives. You can grab a random binary of oggfwd from it's site, or compile shout2send from source. :( MitchellNCharity 17:43, 12 June 2007 (EDT)
- Correction, shout2send is on the olpc. oggfwd is not. --Damonkohler 23:14, 13 September 2007 (EDT)
Doing live streaming video from an xo
Section TODO
- Fill in blank sections.
- Include snapshot recipes.
- Discuss python interfacing.
See also
- Programming the camera
- Video
- Sound
- http://gstreamer.freedesktop.org/
- http://gstreamer.freedesktop.org/documentation/
- Getting started with GStreamer with Python
- Software components ; Sugar Architecture/API#Third_Party_Packages
Other resources
- http://mediamods.com/public-svn/camera-activity/Camera.activity/glive.py
- https://coderanger.net/svn/projects/olpc/games/olpcgames/camera.py (said to not really be working (trouble knowing when gs is done) MitchellNCharity 18:24, 12 June 2007 (EDT))
- Where is the camera code in sugar? MitchellNCharity 18:16, 12 June 2007 (EDT)
- gstreamer-plugins
- gstreamer-plugins-plugin-coreelements
- gst-plugins-base-plugins
- gst-plugins-good-plugins
- google search "site:gstreamer.freedesktop.org"
- http://xiph.org/ Ogg/Theora/Vorbis