开云体育

On Mon, Jan 29, 2024 at 04:44 PM, Paul wrote:

Question - is Loopback_2 used by sbitx?

I don't think so.? gives:



So we have plughw device 0 used for the codec, 1 and 2 used for loopback, leaving the third loopback (numbered 3) unused.


The same search gives a hint of how they get used and how they get created:



Line 20 creates three of them, placed at indices 1,2,3.

Line 14: I found it was important to use the full address:port ( 127.0.0.1:4532 ) not just 127.0.0.1?

I edited the wiki page posted earlier so it has this update.

If yes, could we use this one to route analogue audio I/O from card 0 (audioinjectorpi) on SBITX to another audio I/O device such as a USB headset or Bluetooth headset?

Yes.? Below is a proof of concept.

After connecting my USB headset I ran the command again:

pi@sbitx:~ $ aplay -l | awk -F \: '/,/{print $2}' | awk '{print $1}' | uniq

audioinjectorpi

Loopback

Loopback_1

Loopback_2

II

?

Mine gives:

These suggest it looks promising, the devil is in the detail

Great, I get to play satan!

I am trying to avoid the use of PulseAudio as that has been replaced in newer distributions using Pipewire and Wireplumber, however both of these sit on top of ALSA. Based on this will focus my efforts on using Alsa if possible to minimise complication. Might not be possible but it is a starting point with help from the references above.

Research continues - if I get the answer and tested, it will be added here to begin with and then the wiki page as a Howto
If anyone already solved it then please add to the topic.

I've done a small proof of concept to play sound from sbitx's loop device out to my usb sound card.

What I did to try to make progress was to set up and test wsjt-x using the settings in the wiki page posted earlier.

That told me what device names to use.

Then I tried a few things but in the end what worked for me was to set up a gnuradio flowgraph using its audio source and audio sink.

This is what it looks like:


?
The stuff in the bottom right shows the variables I created, the same stuff is in the text under each variable block.

To be honest I guessed incorrectly based on what wsjt-x refers to as sound card input vs output.??

I used the 'QT GUI Sink' to show a FFT and waterfall of the data and changed names around and it worked.

This is what is known as the FAFO method (f-around, find out).

Then to show it worked, I moved over to the linux CLI and did:

$ arecord -D "plughw:CARD=Loopback,DEV=1" | aplay -D "plughw:CARD=Device,DEV=0"