NAME
gst-launch - build and run a GStreamer pipeline
SYNOPSIS
gst-launch [OPTION...] PIPELINE-DESCRIPTION
DESCRIPTION
gst-launch is a tool that builds and runs basic GStreamer pipelines.
In simple form, a PIPELINE-DESCRIPTION is a list of elements separated
by exclamation marks (!). Properties may be appended to elements, in
the form property=value.
For a complete description of possible PIPELINE-DESCRIPTIONS see the
section pipeline description below or consult the GStreamer documenta-
tion.
Please note that gst-launch is primarily a debugging tool for develop-
ers and users. You should not build applications on top of it. For
applications, use the gst_parse_launch() function of the GStreamer API
as an easy way to construct pipelines from pipeline descriptions.
OPTIONS
gst-launch accepts the following options:
--help Print help synopsis and available FLAGS
-v, --verbose
Output status information
-m, --messages
Output messages posted on the pipeline’s bus
-t, --tags
Output tags (also known as metadata)
-o FILE, --output=FILE
Save XML representation of pipeline to FILE and exit
-f, --no_fault
Do not install a fault handler
-T, --trace
Print memory allocation traces. The feature must be enabled at
compile time to work.
GSTREAMER OPTIONS
gst-launch also accepts the following options that are common to
all GStreamer applications:
--gst-version
Prints the version string of the GStreamer core library.
--gst-fatal-warnings
Causes GStreamer to abort if a warning message occurs. This is
equivalent to setting the environment variable G_DEBUG to
’fatal_warnings’ (see the section environment variables below
for further information).
--gst-debug=STRING
A comma separated list of category_name:level pairs to specify
debugging levels for each category. Level is in the range 0-5
where 0 will show no messages, and 5 will show all messages.
The wildcard * can be used to match category names.
Use --gst-debug-help to show category names
Example: GST_CAT:5,GST_ELEMENT_*:3,oggdemux:5
--gst-debug-level=LEVEL
Sets the threshold for printing debugging messages. A higher
level will print more messages. The useful range is 0-5, with
the default being 0.
--gst-debug-no-color
GStreamer normally prints debugging messages so that the mes-
sages are color-coded when printed to a terminal that handles
ANSI escape sequences. Using this option causes GStreamer to
print messages without color. Setting the GST_DEBUG_NO_COLOR
environment variable will achieve the same thing.
--gst-disable-debug
Disables debugging.
--gst-debug-help
Prints a list of available debug categories and their default
debugging level.
--gst-plugin-spew
GStreamer info flags to set Enable printout of errors while
loading GStreamer plugins
--gst-plugin-path=PATH
Add directories separated with ’:’ to the plugin search path
--gst-plugin-load=PLUGINS
Preload plugins specified in a comma-separated list. Another
way to specify plugins to preload is to use the environment
variable GST_PLUGIN_PATH
PIPELINE DESCRIPTION
A pipeline consists elements and links. Elements can be put into bins
of different sorts. Elements, links and bins can be specified in a
pipeline description in any order.
Elements
ELEMENTTYPE [PROPERTY1 ...]
Creates an element of type ELEMENTTYPE and sets the PROPERTIES.
Properties
PROPERTY=VALUE ...
Sets the property to the specified value. You can use gst-inspect(1) to
find out about properties and allowed values of different elements.
Enumeration properties can be set by name, nick or value.
Bins
[BINTYPE.] ( [PROPERTY1 ...] PIPELINE-DESCRIPTION )
Specifies that a bin of type BINTYPE is created and the given proper-
ties are set. Every element between the braces is put into the bin.
Please note the dot that has to be used after the BINTYPE. You will
almost never need this functionality, it is only really useful for
applications using the gst_launch_parse() API with ’bin’ as bintype.
That way it is possible to build partial pipelines instead of a full-
fledged top-level pipeline.
Links
[[SRCELEMENT].[PAD1,...]] ! [[SINKELEMENT].[PAD1,...]] [[SRCELE-
MENT].[PAD1,...]] ! CAPS ! [[SINKELEMENT].[PAD1,...]]
Links the element with name SRCELEMENT to the element with name
SINKELEMENT, using the caps specified in CAPS as a filter. Names can
be set on elements with the name property. If the name is omitted, the
element that was specified directly in front of or after the link is
used. This works across bins. If a padname is given, the link is done
with these pads. If no pad names are given all possibilities are tried
and a matching pad is used. If multiple padnames are given, both sides
must have the same number of pads specified and multiple links are done
in the given order.
So the simplest link is a simple exclamation mark, that links the ele-
ment to the left of it to the element right of it.
Caps
MIMETYPE [, PROPERTY[, PROPERTY ...]]] [; CAPS[; CAPS ...]]
Creates a capability with the given mimetype and optionally with given
properties. The mimetype can be escaped using " or ’. If you want to
chain caps, you can add more caps in the same format afterwards.
Properties
NAME[:TYPE]=VALUE
in lists and ranges: [TYPE=]VALUE
Sets the requested property in capabilities. The name is an alphanu-
meric value and the type can have the following case-insensitive val-
ues:
- i or int for integer values or ranges
- f or float for float values or ranges
- 4 or fourcc for FOURCC values
- b, bool or boolean for boolean values
- s, str or string for strings
- fraction for fractions (framerate, pixel-aspect-ratio)
- l or list for lists
If no type was given, the following order is tried: integer, float,
boolean, string.
Integer values must be parsable by strtol(), floats by strtod(). FOURCC
values may either be integers or strings. Boolean values are (case
insensitive) yes, no, true or false and may like strings be escaped
with " or ’.
Ranges are in this format: [ PROPERTY, PROPERTY ]
Lists use this format: ( PROPERTY [, PROPERTY ...] )
PIPELINE CONTROL
A pipeline can be controlled by signals. SIGUSR2 will stop the pipeline
(GST_STATE_NULL); SIGUSR1 will put it back to play (GST_STATE_PLAYING).
By default, the pipeline will start in the playing state.
There are currently no signals defined to go into the ready or pause
(GST_STATE_READY and GST_STATE_PAUSED) state explicitely.
PIPELINE EXAMPLES
The examples below assume that you have the correct plug-ins available.
In general, "osssink" can be substituted with another audio output
plug-in such as "esdsink", "alsasink", "osxaudiosink", or "artsdsink".
Likewise, "xvimagesink" can be substituted with "ximagesink",
"sdlvideosink", "osxvideosink", or "aasink". Keep in mind though that
different sinks might accept different formats and even the same sink
might accept different formats on different machines, so you might need
to add converter elements like audioconvert and audioresample (for
audio) or ffmpegcolorspace (for video) in front of the sink to make
things work.
Audio playback
gst-launch filesrc location=music.mp3 ! mad ! audioconvert !
audioresample ! osssink
Play the mp3 music file "music.mp3" using a libmad-based plug-in and
output to an OSS device
gst-launch filesrc location=music.ogg ! oggdemux ! vorbisdec !
audioconvert ! audioresample ! osssink
Play an Ogg Vorbis format file
gst-launch gnomevfssrc location=music.mp3 ! mad ! osssink
gst-launch gnomevfssrc location= !
mad ! audioconvert ! audioresample ! osssink
Play an mp3 file or an http stream using GNOME-VFS
gst-launch gnomevfssrc location=smb://computer/music.mp3 ! mad
! audioconvert ! audioresample ! osssink
Use GNOME-VFS to play an mp3 file located on an SMB server
Format conversion
gst-launch filesrc location=music.mp3 ! mad ! audioconvert !
vorbisenc ! oggmux ! filesink location=music.ogg
Convert an mp3 music file to an Ogg Vorbis file
gst-launch filesrc location=music.mp3 ! mad ! audioconvert !
flacenc ! filesink location=test.flac
Convert to the FLAC format
Other
gst-launch filesrc location=music.wav ! wavparse ! audioconvert
! audioresample ! osssink
Plays a .WAV file that contains raw audio data (PCM).
gst-launch filesrc location=music.wav ! wavparse ! audioconvert
! vorbisenc ! oggmux ! filesink location=music.ogg
gst-launch filesrc location=music.wav ! wavparse ! audioconvert
! lame ! filesink location=music.mp3
Convert a .WAV file containing raw audio data into an Ogg Vorbis or mp3
file
gst-launch cdparanoia ! lame ! filesink location=cd.mp3
rips all tracks from compact disc and convert them into a single mp3
file
Using gst-inspect(1), it is possible to discover settings for cdpara-
noia that will tell it to rip individual tracks. Alternatively, you can
use an URI and gst-launch-0.10 will find an element (such as cdpara-
noia) that supports that protocol for you, e.g.:
gst-launch cdda://5 ! lame vbr=new vbr-quality=6 ! filesink
location=track5.mp3
gst-launch osssrc ! audioconvert ! vorbisenc ! oggmux !
filesink location=input.ogg
records sound from your audio input and encodes it into an ogg file
Video
gst-launch filesrc location=JB_FF9_TheGravityOfLove.mpg ! dvd-
demux ! mpeg2dec ! xvimagesink
Display only the video portion of an MPEG-1 video file, outputting to
an X display window
gst-launch filesrc location=/flflfj.vob ! dvddemux ! mpeg2dec !
sdlvideosink
Display the video portion of a .vob file (used on DVDs), outputting to
an SDL window
gst-launch filesrc location=movie.mpg ! dvddemux name=demuxer
demuxer. ! queue ! mpeg2dec ! sdlvideosink demuxer. ! queue ! mad !
audioconvert ! audioresample ! osssink
Play both video and audio portions of an MPEG movie
gst-launch filesrc location=movie.mpg ! mpegdemux name=demuxer
demuxer. ! queue ! mpeg2dec ! ffmpegcolorspace ! sdlvideosink
demuxer. ! queue ! mad ! audioconvert ! audioresample ! osssink
Play an AVI movie
Network streaming
Stream video using RTP and network elements.
gst-launch v4l2src ! video/x-raw-yuv,width=128,height=96,for-
mat=’(fourcc)’UYVY ! ffenc_h263 ! video/x-h263 ! rtph263ppay pt=96 !
udpsink host=192.168.1.1 port=5000 sync=false
Use this command on the receiver
gst-launch udpsrc port=5000 ! application/x-rtp, clock-
rate=90000,payload=96 ! rtph263pdepay queue-delay=0 ! ffdec_h263 !
xvimagesink
This command would be run on the transmitter
Diagnostic
gst-launch -v fakesrc num-buffers=16 ! fakesink
Generate a null stream and ignore it (and print out details).
gst-launch audiotestsrc ! audioconvert ! audioresample !
osssink
Generate a pure sine tone to test the audio output
gst-launch videotestsrc ! xvimagesink
gst-launch videotestsrc ! ximagesink
Generate a familiar test pattern to test the video output
Automatic linking
You can use the decodebin element to automatically select the right
elements to get a working pipeline.
gst-launch filesrc location=musicfile ! decodebin ! audiocon-
vert ! audioresample ! osssink
Play any supported audio format
gst-launch filesrc location=videofile ! decodebin name=decoder
decoder. ! queue ! audioconvert ! audioresample ! osssink decoder. !
ffmpegcolorspace ! xvimagesink
Play any supported video format with video and audio output. Threads
are used automatically. To make this even easier, you can use the play-
bin element:
gst-launch playbin uri=file:///home/joe/foo.avi
Filtered connections
These examples show you how to use filtered caps.
gst-launch videotestsrc ! ’video/x-raw-yuv,for-
mat=(fourcc)YUY2;video/x-raw-yuv,format=(fourcc)YV12’ ! xvimagesink
Show a test image and use the YUY2 or YV12 video format for this.
gst-launch osssrc ! ’audio/x-raw-
int,rate=[32000,64000],width=[16,32],depth={16,24,32},signed=(boolean)true’
! wavenc ! filesink location=recording.wav
record audio and write it to a .wav file. Force usage of signed 16 to
32 bit samples and a sample rate between 32kHz and 64KHz.
ENVIRONMENT VARIABLES
GST_DEBUG
Comma-separated list of debug categories and levels, e.g.
GST_DEBUG=totem:4,typefind:5
GST_DEBUG_NO_COLOR
When this environment variable is set, coloured debug output is
disabled.
GST_REGISTRY
Path of the plugin registry file. Default is
~/.gstreamer-0.10/registry-CPU.xml where CPU is the machine/cpu
type GStreamer was compiled for, e.g. ’i486’, ’i686’, ’x86-64’,
’ppc’, etc. (check the output of "uname -i" and "uname -m" for
details).
GST_PLUGIN_PATH
Specifies a list of directories to scan for additional plugins.
These take precedence over the system plugins.
GST_PLUGIN_SYSTEM_PATH
Specifies a list of plugins that are always loaded by default.
If not set, this defaults to the system-installed path, and the
plugins installed in the user’s home directory
OIL_CPU_FLAGS
Useful liboil environment variable. Set OIL_CPU_FLAGS=0 when
valgrind or other debugging tools trip over liboil’s CPU detec-
tion (quite a few important GStreamer plugins like videotestsrc,
audioconvert or audioresample use liboil).
G_DEBUG
Useful GLib environment variable. Set G_DEBUG=fatal_warnings to
make GStreamer programs abort when a critical warning such as an
assertion failure occurs. This is useful if you want to find out
which part of the code caused that warning to be triggered and
under what circumstances. Simply set G_DEBUG as mentioned above
and run the program in gdb (or let it core dump). Then get a
stack trace in the usual way.
FILES
~/.gstreamer-0.10/registry-*.xml
The xml plugin database; can be deleted at any time, will be
re-created automatically when it does not exist yet or plugins
change.
SEE ALSO
gst-feedback(1), gst-inspect(1), gst-typefind(1)
AUTHOR
The GStreamer team at
