Overwitch, a JACK client for Overbridge devices, AKA Overbridge for Linux

The Lounge General Discussion
44

WRT recording the audio to file you could do something like this.

First and foremost install jack_capture and run JACK and Overwitch as stated above.

Then, let’s see all the JACK ports and how they are connected. My audio interface is a Soundcraft Signature MTK12 (14 inputs and 12 outputs). For the sake of brevity I’ll omit some ports.

$ jack_lsp -c
[...]
system:playback_11
system:playback_12
Digitakt:Main L
Digitakt:Main R
Digitakt:Track 1
Digitakt:Track 2
[...]
Digitakt:Track 7
Digitakt:Track 8
Digitakt:Input L
Digitakt:Input R
Digitakt:Main L Input
Digitakt:Main R Input
[...]

From here, let’s monitor something. I’ll connect the main output to the stereo pair I’m monitoring thru my headphones.

$ jack_connect "Digitakt:Main L" system:playback_11
$ jack_connect "Digitakt:Main R" system:playback_12

And let’s run jack_lsp -c again. We’ll see the connections.

$ jack_lsp -c
[...]
system:playback_11
   Digitakt:Main L
system:playback_12
   Digitakt:Main R
Digitakt:Main L
   system:playback_11
Digitakt:Main R
   system:playback_12
Digitakt:Track 1
Digitakt:Track 2
[...]
Digitakt:Track 7
Digitakt:Track 8
Digitakt:Input L
Digitakt:Input R
Digitakt:Main L Input
Digitakt:Main R Input
[...]

Now, let’s just record what we want. For instance, the 8 mono tracks.

$ chrt -f 35 jack_capture -b 16 -c 8 -p "Digitakt:Track 1" -p "Digitakt:Track 2" -p "Digitakt:Track 3" -p "Digitakt:Track 4" -p "Digitakt:Track 5" -p "Digitakt:Track 6" -p "Digitakt:Track 7" -p "Digitakt:Track 8" foo.wav
>>> Warning. Could not set higher priority for a SCHED_OTHER process using setpriority().
>>> Recording to "foo.wav". Press <Return> or <Ctrl-C> to stop.
>>> Please wait while writing all data to disk. (shouldn't take long)   
   |"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""|
00:|-----------                    *                                 |
01:|-------------               *                                    |
02:|--------------------------- *                                    |
03:|                                                                 |
04:|-------                     *                                    |
05:|---------                *                                       |
06:|                                                                 |
07:|                                                                 |
Buffer: 4.01s./4.01s    Time: 0.28m.   DHP: [ ]  Overruns: 0  Xruns: 0
Finished.

And there it is. An 8 channel WAVE file directly streamed to disk while monitoring the device mix.

$ sox --i foo.wav 

Input File     : 'foo.wav'
Channels       : 8
Sample Rate    : 48000
Precision      : 16-bit
Duration       : 00:00:28.08 = 1347712 samples ~ 2105.8 CDDA sectors
File Size      : 21.6M
Bit Rate       : 6.14M
Sample Encoding: 16-bit Signed Integer PCM

By the way, these are the reported latencies. No Xruns.

$ chrt -f 35 overwitch -q 2 -d Digitakt -b 8
Device: Digitakt (outputs: 12, inputs: 2)
JACK sample rate: 48000
JACK buffer size: 64
^CMax. latencies (ms): 3.5, 3.4

Edit: I forgot to mention that I’ve fixed the bug in the device selection.

5 Likes