pipewire/README.md
2020-05-02 08:16:03 +00:00

4 KiB

PipeWire

PipeWire is a server and user space API to deal with multimedia pipelines. This includes:

  • Making available sources of video (such as from a capture devices or application provided streams) and multiplexing this with clients.
  • Accessing sources of video for consumption.
  • Generating graphs for audio and video processing.

Nodes in the graph can be implemented as separate processes, communicating with sockets and exchanging multimedia content using fd passing.

Building and installation

The prefered way to install PipeWire is to install it with your distribution package system. This ensures PipeWire is integrated into the rest of your system for the best experience.

If you want to build and install PipeWire yourself, refer to INSTALL.md for instructions.

Usage

The most important purpose of PipeWire is to run your favorite apps.

Some application use the native PipeWire API, such as most compositors (gnome-shell, wayland, ..) to implement screen sharing. These apps will just work automatically.

Most audio applications can use either ALSA, JACK or PulseAudio as a backend. PipeWire provides support for all 3 backends. Depending on how your distríbution has configured things this should just work automatically or with the provided scripts shown below.

PipeWire can use environment variables to control the behaviour of applications:

  • PIPEWIRE_DEBUG= to increase the debug level
  • PIPEWIRE_LOG= to redirect log to filename
  • PIPEWIRE_LATENCY=<num/denom> to configure latency
  • PIPEWIRE_NODE= to request link to specified node

Using tools

pw-cat can be used to play and record audio and midi. Use pw-cat -h to get some more help. There are some aliases like pw-play and pw-record to make things easier:

$ pw-play /home/wim/data/01.\ Firepower.wav

Running JACK applications

Depending on how the system was configured, your can either run PipeWire and JACK side-by-side or have PipeWire take over the functionality of JACK completely.

In dual mode, JACK apps will by default use the JACK server. To direct a JACK app to PipeWire, you can use the pw-jack script like this:

$ pw-jack <appname>

If you replaced JACK with PipeWire completely, pw-jack does not have any effect and can be ommited.

Running PulseAudio applications

Depending on how the system was configured, your can either run PipeWire and PulseAudio side-by-side or have PipeWire take over the functionality of PulseAudio completely. We don't recommend to completely replace PulseAudio at this point.

Use the pw-pulse script to launch a PulseAudio application on PipeWire, like:

$ pw-pulse <appname>

Running ALSA applications

If the PipeWire alsa module is installed, it can be seen with

$ aplay -L

Alsa application can then use the pipewire: device to use PipeWire as the audio system.

Running GStreamer applications

PipeWire includes 2 GStreamer elements called pipewiresrc and pipewiresink. They can be used in pipelines like this:

$ gst-launch-1.0 pipewiresrc ! videoconvert ! autovideosink

Or to play a beeping sound:

$ gst-launch-1.0 audiotestsrc ! pipewiresink

PipeWire provides a device monitor as well so that:

$ gst-device-monitor-1.0

Shows the PipeWire devices and applications like cheese will automatically use the PipeWire video source when possible.

Inspecting the PipeWire state

There is currently no native graphical tool to inspect the PipeWire graph but we recommend to use one of the excellent JACK tools, such as Carla, catia, qjackctl,... You will not be able to see all features like the video ports but it is a good start.

pw-mon dumps and monitors the state of the PipeWire daemon.

pw-dot can dump a graph of the pipeline, checkout out the help for how to do this.

There is a more complicated tools to inspect the state of the server with pw-cli. This tools can be used interactively or it can execute single commands like this to get the server information:

$ pw-cli info 0