linux – Does the ALSA “plug” auto-conversion plugin interfere ondemand only?

Background

We develop a Debian-based Linux distribution and some users face the issue that some audio sources cannot be played, because the sound card does not natively support the audio format.

We provide a configuration script for audio/ALSA setup and by default use the native hw plugin. There is the plug auto-conversion plugin which automatically converts the audio stream to a format which is supported by the sound card, but it is disabled by default, since software conversion leads to increased CPU utilisation and decreased audio quality.

However, if the conversion was done only when really required, there would be now downside, but only the upside that all audio sources can be played, regardless whether the sound card natively supports the source format or not.

Question

The question hence is whether the plug ALSA plugin really is a no-op for audio streams supported by the sound card, neither increasing CPU utilisation, not degrading audio quality.

No one of our team has a sufficiently high quality sound system to reliably test it, and when it comes to audio quality, it is prone to subjective and information-biased perception. Also I couldn’t find a definit information in the related ALSA documentation or elsewhere via search machines. Hence I hope for some expertise here.

Reference

Here the official ALSA plug plugin documentation: www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html#pcm_plugins_plug