gstreamer/subprojects/gst-docs/markdown/tools/gst-launch.md

# gst-launch-1.0

> ![information] 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`. A "preset" can also be set using
the `@preset=<preset name>` syntax.

For a more complete description of possible PIPELINE-DESCRIPTIONS see the
section [Pipeline Description](#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, write a little python
script or Rust application (or use whatever other programming language you
prefer) and 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)

**-e, --eos-on-shutdown**

Force an EOS event on sources before shutting the pipeline down. This is
useful to make sure muxers create readable files when a muxing pipeline is
shut down forcefully via Control-C (especially in case of `mp4mux` and `qtmux`
where the created file will be unreadable if the file has not been finalised
properly).

**-f, --no\_fault**

Do not install a segfault handler

**--no-position**

Do not print the current position of pipeline.

If this option is unspecified, the position will be printed when stdout is a TTY.
To enable printing position when stdout is not a TTY,
use the "--force-position" option.

**--force-position**

Allow printing the current position of pipeline even if stdout is not a TTY.
This option has no effect if the "--no-position" option is specified.


## GStreamer Options

`gst-launch-1.0` 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=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 0-9 where 0 will show no messages, and
9 will show all messages. The wildcard `*` can be used to match category names.

Note that the order of categories and levels is important, wildcards at the
end may override levels set earlier. The log levels are:

1. ERROR
2. WARNING
3. FIXME
4. INFO
5. DEBUG
6. LOG (this is the highest 'normal' debug level)
7. TRACE
9. MEMDUMP

Since GStreamer 1.2 one can also use the debug level names, e.g.
`--gst-debug=*sink:LOG`. A full description of the various debug levels
can be found in the GStreamer core library API documentation, in the
"Running GStreamer Applications" section.

Use `--gst-debug-help` to show category names

Example: `GST_CAT:LOG,GST_ELEMENT_*:INFO,oggdemux:LOG`

**--gst-debug-level=LEVEL**

Sets the threshold for printing debugging messages.  A higher level
will print more messages.  The useful range is 0-9, with the default
being 0. Level 6 (LOG level) will show all information that is usually
required for debugging purposes. Higher levels are only useful in very
specific cases. See above for the full list of levels.

**--gst-debug-no-color**

`GStreamer` normally prints debugging messages so that the
messages 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=1`
environment variable will achieve the same thing.

**--gst-debug-color-mode**

GStreamer normally prints debugging messages so that the
messages are color-coded when printed to a terminal that handles
ANSI escape sequences (on *nix), or uses W32 console API to color the
messages printed into a console (on W32). Using this option causes
GStreamer to print messages without color ('off' or 'disable'),
print messages with default colors ('on' or 'auto'), or print messages
using ANSI escape sequences for coloring ('unix'). Setting the
`GST_DEBUG_COLOR_MODE` environment variable will achieve the same thing.

**--gst-debug-disable**

Disables debugging.

**--gst-debug-help**

Prints a list of available debug categories and their default debugging level.

**--gst-plugin-path=PATH**

Add directories separated with `:` (`;` on Windows) 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 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.

### Element Presets

```
@preset=<preset name> ...
```

Sets the preset (basically a pre-made collection of property settings for a
specific element) on the element. you can use `gst-inspect-1.0` to
find out what presets are available for a specific element.

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

Linking using the `:` operator attempts to link all possible pads between
the elements

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;
- `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()`.
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]`, e.g. `width=[16,1920]`

Lists use this format: `{VALUE [, VALUE ...]}`, e.g. `width={1920,1280,640}`

## Pipeline Examples

The examples below assume that you have the correct plug-ins available.
In general, "pulsesink" can be substituted with another audio output
plug-in such as "alsasink", "osxaudiosink", or "wasapisink"

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 `videoconvertscale` in front of the sink to make things work.

### Audio playback

**Note:** For audio/video playback it's best to use the `playbin3` or
`uridecodebin3` elements, these are just example pipelines.

Play the mp3 music file "music.mp3" using a libmpg123-based plug-in and
output it to an audio device via PulseAudio (or PipeWire).

```
gst-launch-1.0 filesrc location=music.mp3 ! mpegaudioparse ! mpg123audiodec ! audioconvert ! audioresample ! pulsesink
```

Play an Ogg Vorbis format file:

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

Play an mp3 file or an http stream using GIO:

```
gst-launch-1.0 giosrc location=music.mp3 ! mpegaudioparse ! mpg123audiodec ! audioconvert ! pulsesink
```

```
gst-launch-1.0 giosrc location=http://domain.com/music.mp3 ! mpegaudioparse ! mpg123audiodec ! audioconvert ! audioresample ! pulsesink
```

Use GIO to play an mp3 file located on an SMB server:

```
gst-launch-1.0 giosrc location=smb://computer/music.mp3 ! mpegaudioparse ! mpg123audiodec ! audioconvert ! audioresample ! pulsesink
```

### Format conversion

Convert an mp3 music file to an Ogg Vorbis file:

```
gst-launch-1.0 filesrc location=music.mp3 ! mpegaudioparse ! mpg123audiodec ! audioconvert ! vorbisenc ! oggmux ! filesink location=music.ogg
```

Convert to the FLAC format:

```
gst-launch-1.0 filesrc location=music.mp3 ! mpegaudioparse ! mpg123audiodec ! 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 ! pulsesink
```

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 ! lamemp3enc ! xingmux ! id3v2mux ! 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 ! lamemp3enc ! mpegaudioparse ! xingmux ! 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 ! lamemp3enc ! mpegaudioparse ! xingmux ! 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 ! lamemp3enc vbr=new vbr-quality=6 ! xingmux ! id3v2mux ! filesink location=track5.mp3
```

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

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

### Video

**Note:** For audio/video playback it's best to use the `playbin3` or
`uridecodebin3` elements, these are just example pipelines.

Display only the video portion of an MPEG-2 video file, outputting to an X
display window:

```
gst-launch-1.0 filesrc location=JB_FF9_TheGravityOfLove.mpg ! mpegdemux ! mpegvideoparse ! mpeg2dec ! videoconvert ! 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 ! mpegvideoparse ! mpeg2dec ! videoconvert ! sdlvideosink
```

Play both video and audio portions of an MPEG movie:

```
gst-launch-1.0 filesrc location=movie.mpg ! dvddemux name=demuxer  \
\
demuxer. ! queue ! mpegvideoparse ! mpeg2dec ! videoconvert ! sdlvideosink \
demuxer. ! queue ! mpegaudioparse ! mpg123audiodec ! audioconvert ! audioresample ! pulsesink
```

Play an AVI movie with an external text subtitle stream:

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 ! decodebin3 !  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 playbin3 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 ! queue ! videoconvert ! x264enc tune=zerolatency key-int-max=15 ! video/x-h264,profile=main ! rtph264pay pt=96 config-interval=-1 ! udpsink host=192.168.1.1 port=5000
```

Use this command on the receiver:

```
gst-launch-1.0 udpsrc port=5000 ! application/x-rtp,clock-rate=90000,payload=96 ! rtpjitterbuffer ! rtph264depay ! h264parse ! avdec_h264 ! videoconvert ! xvimagesink
```

### Diagnostic

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

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

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
```

```
gst-launch-1.0 videotestsrc ! xvimagesink
```

### Automatic linking

You can use the "decodebin3" element to automatically select the right
elements to get a working pipeline.

Play any supported audio format:

```
gst-launch-1.0 filesrc location=musicfile ! decodebin3 ! audioconvert ! audioresample ! pulsesink
```

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 ! pulsesink   decoder. !  videoconvert ! xvimagesink
```

You can also support different inputs by using an URI and uridecodebin3, e.g.:

```
gst-launch-1.0 uridecodebin3 uri=file:///path/to/video.mp4 name=decoder decoder. ! queue ! audioconvert ! audioresample ! pulsesink   decoder. !  videoconvert ! xvimagesink
```

```
gst-launch-1.0 uridecodebin3 uri=https://gstreamer.freedesktop.org/data/media/sintel_trailer-480p.webm name=decoder decoder. ! queue ! audioconvert ! audioresample ! pulsesink   decoder. !  videoconvert ! xvimagesink
```

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

```
gst-launch-1.0 playbin3 uri=file:///home/joe/foo.avi
```

```
gst-launch-1.0 playbin3 uri=https://gstreamer.freedesktop.org/data/media/sintel_trailer-480p.webm
```

### 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,format=YUY2;video/x-raw,format=YV12' ! xvimagesink
```

or

```
gst-launch-1.0 v4l2src ! image/jpeg ! queue ! decodebin3 ! videoconvert ! autovideosink
```

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 pulsesrc !  'audio/x-raw,rate=[32000,64000],format={S16LE,S24LE,S32LE}' ! 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
```

`*` is allowed as a wildcard as part of debug category names (e.g.
`GST_DEBUG=*sink:6,*audio*:6`). It is also possible to specify the log level
by name (1=ERROR, 2=WARN, 3=FIXME, 4=INFO, 5=DEBUG, 6=LOG, 7=TRACE, 9=MEMDUMP),
e.g. `GST_DEBUG=*audio*:LOG`.

`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.

These can then later be converted into an image using the 'dot' utility from
the graphviz set of tools, like this: `dot foo.dot -Tsvg -o foo.svg` (png or jpg
are also possible as output format). There is also a utility called `xdot`
which allows you to view the .dot file directly without converting it first.

When the pipeline changes state through NULL to PLAYING and back to NULL, a
dot file is generated on each state change. To write a snapshot of the
pipeline state, send a SIGHUP to the process or use the pipeline_snapshot
tracer from the GStreamer Rust plugins.

`GST_REGISTRY`: Path of the plugin registry file. The default is
`~/.cache/gstreamer-1.0/registry-CPU.xml` where CPU is the machine/cpu type
GStreamer was compiled for, e.g. 'x86_64', 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

`GST_DEBUG_FILE`: Set this variable to a file path to redirect all GStreamer
debug messages to this file. If left unset, debug messages will be output
to the standard error output.

`ORC_CODE`: Useful Orc environment variable. Set `ORC_CODE=debug` to enable
debuggers such as gdb to create useful backtraces from Orc-generated code.  Set
`ORC_CODE=backup` or `ORC_CODE=emulate` if you suspect Orc's SIMD code
generator is producing incorrect code.  (Quite a few important
GStreamer plugins like videotestsrc, audioconvert or audioresample use Orc).

`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.

  [information]: images/icons/emoticons/information.svg