. I did some early PC sound card audio quality testing and published result on my web pages for several sound cards. That lead me later to take part in making one of the first PC sound quality measurement standard “Personal Computer Audio Quality Measurements 1.00″ started by Cirrus Logic in the later 1990′s. I contributed to standard and reviewed the technical material. Quality levels for some of these measurements are suggested in Microsoft’s PC ‘97, PC ’98, PC ‘99, Intel’s AC ‘97, and in the MPC3 specification.

Sound System Overview

Someone once said, “The nice thing about standards is there are so many of them.” This is true for Linux sound, too. The most common way to access a soundcard is via ALSA, also known as Advanced Linux Sound Architecture. There are other methods, but this is somewhat the lowest common denominator on most modern systems.

However, most modern systems add one or more layers so you can do things like easily redirect sound from a speaker to a headphone, for example. Or ship audio over the network.

The most common layer over ALSA is PulseAudio, and for many years, it was the most common standard. These days, you see many distros moving to PipeWire.

PipeWire is newer and has a lot of features but perhaps the best one is that it is easy to set it up to look like PulseAudio. So software that understands PipeWire can use it. Programs that don’t understand it can pretend it is PulseAudio.

There are other systems, too, and they all interoperate in some way. While OSS is not as common as it once was, JACK is still found in certain applications. Many choices!

One Way

There are many ways you can accomplish what I was after. Since I am running PipeWire, I elected to use qpwgraph, which is a GUI that shows you all the sound devices on the system and lets you drag lines between them.

It is super powerful but also super cranky. As things change, it tends to want to redraw the “graph,” and it often does it in a strange and ugly way. If you name a block to help you remember what it is and then disconnect it, the name usually goes back to the default. But these are small problems, and you can work around them.

In theory, you should be able to just grab the output and “wire” it to the other program’s input. In fact, that works, but there is one small problem. Both PipeWire and PulseAudio will show when a program is making sound, and then, when it stops, the source vanishes.