Linux: sound and devices

Everything here is about one question: which output the game plays through. On Linux that question has more than one answer, and the machine does not always agree with itself about which is right.

See which output was taken

The game states it once, at startup, and you do not need to raise the log level:

grep 'stage="output"' logs/game.log

A healthy line names the output and the format the machine reports for it:

INFO ironlark::audio: opened stage="output" output=PipeWire Sound Server (44100 Hz, 2 ch, F32)

The role in the filename follows how you started: host.log with --become-host, client.log with --connect-to, game.log otherwise.

The game is the only application with no sound

That symptom has one common cause on Linux, and it is not the game’s settings.

A desktop runs a sound server — PipeWire on most systems now, PulseAudio before it — and the server owns the hardware. Applications reach it in one of two ways: they speak the server’s own protocol, or they go through ALSA and rely on ALSA’s default being routed to the server. That routing is a configuration file, and it is not always in place. When it is missing, default addresses a sound card directly — often the first one, which on a machine with an external interface is the one nobody is listening to.

The result is a game that opens an output successfully and plays into it while you hear nothing, because your speakers are on a different card.

The game prefers the sound server over default when the server is already running, which is what makes this work without configuration. What follows is for the machines where you want to choose yourself.

Choose the output yourself

In config/server.toml beside the game:

[audio]
device = "pipewire"

Either name works: the system’s own name for an output, or the name a person reads.

default is the one value that is not an output. It asks for whatever the game would have chosen on its own, which is how a setting is undone without editing the key away:

[audio]
device = "default"

A pinned output is not followed

A device you name is the one the game keeps. Unplug it and the game does not move to another; the sound server does that for you only while the game is playing through the server rather than through a card you named.

See what you could have named

Name something that does not exist, and the refusal carries the whole list:

grep 'no output of this' logs/game.log

The names are the ones ALSA publishes, so aplay -L shows the same set.

Turn game sound off

[audio]
enabled = false

Nothing is opened at all, which is also the answer when a driver writes complaints to the terminal that no log level of ours can filter.

Trace the whole path

Every audio record carries a stage, and the stages are the path a sound takes: settings, output, bus, decode, gate, start, advance, end, summary. To follow one sound:

grep 'ironlark::audio' logs/game.log

advance is per-frame and off unless asked for. It reports the playback position of every sound in flight, which is how a mixer that has stopped moving is told apart from one that is playing where you cannot hear it:

RUST_LOG="ironlark::audio=trace" ./ironlark-game

The console stays quiet at its usual level; the extra detail goes to the file.