Hello,

a Tails user just reported it on IRC and I report it here as I had the same thought too for a while.

Possibly it’s better to mute the audio or set the volume to zero at boot time because system sounds and accidentially run audio/video files could raise suspicion.

Maybe it’s better to let the user do the 2 clicks to enable it, just to be on the safe side.

—JohnDoe

Why not, thanks for mentioning it. Care to bring us a patch? —intrigeri

Inspiration sources

• The "Small patch to mute sound on boot time" thread on tails-dev; last patch attached here.
• Debian’s alsa-utils initscript and its /usr/share/alsa/utils.sh library deals with channel levels in a way that supports many specific tricks needed by various hardware.
• Liberte Linux’ src/usr/local/bin/reset-mixer (which seems to only mute the first sound-card, and supports a limited set of controls, and therefore a limited set of hardware).

Implementation issues

What channel(s) shall be muted?

According to the archlinux documentation, "ALSA installs with all channels muted by default"; indeed, most of the work done by the alsa-utils initscript in Debian is merely to unmute many channels and toggle many controls.

If we mute all possible channels, most users won’t know what hardware-dependent list of channels they must unmute and increase level in order to get sound output.

So we may want to mute only the Master channel. However, this would only be a partial implementation of the stated goal: it seems there are ALSA drivers that don’t expose a Master channel, e.g. see this bug report.