Here's a summary of all the PulseAudio specific terms (note that the words that PulseAudio uses do not match the typical use of that word):
input
: digital audio stream from an application to PulseAudio (e.g. audio from Youtube video playing in your web browser). Note that this has nothing to do with any physical connector that your system has.
output
: digital audio stream from PulseAudio to application (e.g. recorded microphone audio to be sent to video conference by your browser). Note that this has nothing to do with any physical connector that your system has.
source
: device that can emit digital audio stream to PulseAudio (typically microphone, line input, HDMI capture card or something similar; may or may not be backed by actual audio hardware but PulseAudio will treat it as if it was real hardware)
sink
: device that can output digital audio stream from PulseAudio (typically speaker signal, headphone output, HDMI output, line out; may or may not be backed by actual audio hardware but PulseAudio will treat it as if it was real hardware)
PulseAudio will then create combinations of these. For example, pacmd list-source-outputs
will list digital streams from some source
to some output
, basically the connections between source
devices (hardware) and software output
s (applications).
If no application is currently taking digital streams, there are no connections even though applications that support PulseAudio are running and hardware that's able to generate audio streams are available (that is, connection exists only when application actively captures audio). I personally think that it would make more sense to call these as recording-streams
or something like that but PulseAudio authors call these source-outputs
instead.
It may help to think PulseAudio as a virtual mixing desk that has applications (input
and output
) and hardware (source
and sink
) connected to it and it will route streams/connections between different things.
pacmd list-source-outputs
) – what on earth is that supposed to mean? – Mikko Rantalainen Nov 22 '21 at 20:21