gstreamer/markdown/tools/gst-launch.md

gst-launch-1.0

This content comes mostly from the Linux man page for the gst-launch-1.0 tool. As such, it is very Linux-centric regarding path specification and plugin names. Please be patient while it is rewritten to be more generic.

Name

gst-launch-1.0 - build and run a GStreamer pipeline

Synopsis

gst-launch-1.0 [OPTIONS] PIPELINE-DESCRIPTION

Description

gst-launch-1.0 is a tool that builds and runs basic GStreamer pipelines.

In its simplest 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 more complete description of possible PIPELINE-DESCRIPTIONS see the section Pipeline Description below or consult the GStreamer documentation.

Please note that gst-launch-1.0 is primarily a debugging tool. 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-1.0 accepts the following options:

--help

Print help synopsis and available FLAGS

-v, --verbose

Output status information and property notifications

-q, --quiet

Do not print any progress 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-1.0 also accepts the following options that are common to all GStreamer applications:

Pipeline Description

A pipeline consists of 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 its PROPERTIES.

Element Properties

PROPERTY=VALUE ...

Sets the property to the specified value. You can use gst-inspect-1.0 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 properties 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_parse_launch() 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,...]]

Links the element with name SRCELEMENT to the element with name SINKELEMENT. Names can be set on elements using 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 using that pad. If no pad names are given all possibilities are tried and a compatible 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. The simplest link is a simple exclamation mark. This links the element to the left of it with the element at its right.

The following links the element with name SRCELEMENT to the element with name SINKELEMENT, using the caps specified in CAPS as a filter:

[[SRCELEMENT].[PAD1,...]] ! CAPS ! [[SINKELEMENT].[PAD1,...]]

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.

Caps Properties

NAME=[(TYPE)] VALUE in lists and ranges: [(TYPE)] VALUE

Sets the requested property in capabilities. The name is an alphanumeric value and the type can have the following case-insensitive values:

• 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: [ VALUE, VALUE]; lists use this format: (VALUE [, VALUE ...]).

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) states explicitly.

Pipeline Examples

The examples below assume that you have the correct plugins available. In general, osssink can be substituted with another audio output plugin such as directsoundsink, esdsink, alsasink, osxaudiosink, or artsdsink. Likewise, xvimagesink can be substituted with d3dvideosink, 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 videoconvert in front of the sink to make things work.

Audio playback

Play the mp3 music file "music.mp3" using a libmad-based plugin and output to an OSS device:

gst-launch-1.0 filesrc location=music.mp3 ! mad ! audioconvert !
audioresample ! osssink

Play an Ogg Vorbis format file:

gst-launch-1.0 filesrc location=music.ogg ! oggdemux ! vorbisdec !
audioconvert ! audioresample ! osssink

Play an mp3 file using GNOME-VFS:

gst-launch-1.0 gnomevfssrc location=music.mp3 ! mad ! osssink

Play an HTTP stream using GNOME-VFS:

gst-launch-1.0 gnomevfssrc location=<http://domain.com/music.mp3> ! mad
! audioconvert ! audioresample ! osssink

Use GNOME-VFS to play an mp3 file located on an SMB server:

gst-launch-1.0 gnomevfssrc location=<smb://computer/music.mp3> ! mad !
audioconvert ! audioresample ! osssink

Format conversion

Convert an mp3 music file to an Ogg Vorbis file:

gst-launch-1.0 filesrc location=music.mp3 ! mad ! audioconvert ! vorbisenc !
oggmux ! filesink location=music.ogg

Convert to the FLAC format:

gst-launch-1.0 filesrc location=music.mp3 ! mad ! audioconvert ! flacenc !
filesink location=test.flac`

Other

Play a .WAV file that contains raw audio data (PCM):

gst-launch-1.0 filesrc location=music.wav ! wavparse ! audioconvert !
audioresample ! osssink

Convert a .WAV file containing raw audio data into an Ogg Vorbis or mp3 file:

gst-launch-1.0 filesrc location=music.wav ! wavparse ! audioconvert !
vorbisenc ! oggmux ! filesink location=music.ogg

gst-launch-1.0 filesrc location=music.wav ! wavparse ! audioconvert ! lame !
filesink location=music.mp3

Rip all tracks from CD and convert them into a single mp3 file:

gst-launch-1.0 cdparanoiasrc mode=continuous ! audioconvert ! lame !
id3v2mux ! filesink location=cd.mp3

Rip track 5 from the CD and converts it into a single mp3 file:

gst-launch-1.0 cdparanoiasrc track=5 ! audioconvert ! lame ! id3v2mux
! filesink location=track5.mp3

Using gst-inspect-1.0, it is possible to discover settings like the above for "cdparanoiasrc" that will tell it to rip the entire CD or only tracks of it. Alternatively, you can use an URI and gst-launch-1.0 will find an element (such as cdparanoia) that supports that protocol for you, e.g.:

gst-launch-1.0 [cdda://5] ! lame vbr=new vbr-quality=6 !
filesink location=track5.mp3

Record sound from your audio input and encode it into an ogg file:

gst-launch-1.0 osssrc ! audioconvert ! vorbisenc ! oggmux !
filesink location=input.ogg

Video

Display only the video portion of an MPEG-1 video file, outputting to an X display window:

gst-launch-1.0 filesrc location=videofile.mpg ! dvddemux ! mpeg2dec !
xvimagesink

Display the video portion of a .vob file (used on DVDs), outputting to an SDL window:

gst-launch-1.0 filesrc location=flflfj.vob ! dvddemux ! mpeg2dec ! sdlvideosink

Play both video and audio portions of an MPEG movie:

gst-launch-1.0 filesrc location=movie.mpg ! dvddemux name=demuxer
demuxer. ! queue ! mpeg2dec ! sdlvideosink
demuxer. ! queue ! mad !  audioconvert ! audioresample ! osssink

Play an AVI movie with an external text subtitle stream:

gst-launch-1.0 filesrc location=movie.mpg ! mpegdemux name=demuxer
demuxer. ! queue ! mpeg2dec ! videoconvert ! sdlvideosink
demuxer. ! queue ! mad ! audioconvert ! audioresample ! osssink

This example shows how to refer to specific pads by name if an element (here: textoverlay) has multiple sink or source pads:

gst-launch-1.0 textoverlay name=overlay ! videoconvert ! videoscale !
autovideosink
filesrc location=movie.avi ! decodebin2 !  videoconvert ! overlay.video_sink
filesrc location=movie.srt ! subparse ! overlay.text_sink

Play an AVI movie with an external text subtitle stream using playbin:

gst-launch-1.0 playbin uri=<file:///path/to/movie.avi>
suburi=<file:///path/to/movie.srt>

Network streaming

Stream video using RTP and network elements

This command would be run on the transmitter:

gst-launch-1.0 v4l2src !
video/x-raw-yuv,width=128,height=96,format='(fourcc)'UYVY !
videoconvert ! 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-1.0 udpsrc port=5000 ! application/x-rtp,
clock-rate=90000,payload=96 ! rtph263pdepay queue-delay=0 ! ffdec_h263
! xvimagesink

Diagnostic

Generate a null stream and ignore it (and print out details):

gst-launch-1.0 -v fakesrc num-buffers=16 ! fakesink

Generate a pure sine tone to test the audio output:

gst-launch-1.0 audiotestsrc ! audioconvert ! audioresample ! osssink

Generate a familiar test pattern to test the video output:

gst-launch-1.0 videotestsrc ! ximagesink

Automatic linking

You can use the "decodebin" element to automatically select the right elements to get a working pipeline.

Play any supported audio format:

gst-launch-1.0 filesrc location=musicfile ! decodebin ! audioconvert !
audioresample ! osssink

Play any supported video format with video and audio output. Threads are used automatically:

gst-launch-1.0 filesrc location=videofile ! decodebin name=decoder
decoder. ! queue ! audioconvert ! audioresample ! osssink
decoder. ! videoconvert ! xvimagesink

To make the above even easier, you can use the playbin element:

gst-launch-1.0 playbin uri=<file:///home/joe/foo.avi>

Filtered connections

These examples show you how to use filtered caps.

Show a test image and use the YUY2 or YV12 video format for this:

gst-launch-1.0 videotestsrc !
'video/x-raw-yuv,format=(fourcc)YUY2;video/x-raw-yuv,format=(fourcc)YV12'
! xvimagesink

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:

gst-launch-1.0 osssrc !
'audio/x-raw-int,rate=[32000,64000],width=[16,32],depth={16,24,32},signed=(boolean)true'
! wavenc ! filesink location=recording.wav

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. This might come handy when saving the debug output to a file.

GST_DEBUG_DUMP_DOT_DIR: When set to a filesystem path, store dot files of pipeline graphs there.

GST_REGISTRY: Path of the plugin registry file. The default is ~/.gstreamer-1.0/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_REGISTRY_UPDATE: Set to "no" to force GStreamer to assume that no plugins have changed, have been added or have been removed. This will make GStreamer skip the initial check to determine whether a rebuild of the registry cache is required or not. This may be useful in embedded environments where the installed plugins never change. Do not use this option in any other setup.

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 detection. Quite a few important GStreamer plugins like videotestsrc, audioconvert and audioresample use liboil.

G_DEBUG: This is a 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 under gdb (or let it core dump). Then get a stack trace in the usual way.