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Situation:

  • I'm teaching language lessons over Skype
  • I'm recording "demonstration" sessions
  • The basic pattern is:
    • (1) - the teacher gives a prompt
    • (2) - then the student thinks for a second then answers
  • This pattern repeats for an hour or two each session
  • I need to record the two tracks separately, but keep them in sync over the whole session

When I say, "keep them in sync",
I don't mean compensating for the lag of the VOIP connection;
That lag is very minor (and constant anyway).

What I mean is:
I just want to record the teacher and student audio to two separate tracks
but keep them sync'd up exactly the same way I originally hear them on my end.

So the two tracks are:

  • Teacher:
    • this is me
    • local, outgoing
    • coming from an external microphone that has two outputs: a USB output and an analog (both outputs can be used simultaneously) (this microphone)
    • currently, I'm using the USB output to send over Skype, and not using the analog output at all (although it worked fine when I tested it earlier)
  • Student:
    • incoming audio from Skype

I've been recording the tracks on the same computer that's running Skype
(through ffmpeg and pulseaudio on linux)
but the tracks drift out of sync.
(And I don't believe there is a software solution to that with the setup I'm stuck with.)

So I want to get some new, separate hardware to completely sidestep the software stack.

That is, I'd like to continue using the current computer for Skype,
but record both analog tracks on a separate piece of hardware.

So I think I want to do something like:

and

  • tap the analog output from the microphone (the teacher track)
    (again, currently, I'm not using the analog microphone output; only the simultaneous USB output to feed into Skype)

and

  • feed both analog inputs into a new, separate piece of hardware to be recorded in sync

(
Again,
by "in sync" I mean that I want the rate of the two tracks to not gradually drift apart over the session.
*I just want them to stay at the same rate I originally hear them at on my end;*
nothing to do with compensating for the network lag over Skype.
)

So I want some hardware that can take two separate analog inputs,
and can reliably record them in sync, as two separate files.
(
It would also be fine to record two separate channels in the same recording (like left/right),
so long as the tracks don't get mixed together.
)

Now, I could probably build something like that myself...
for instance, take something like:
this Raspberry Pi
and put it together with something like:
this soundcard
and then fiddle around for a week figuring out good softward setup to run on it...?

But ideally, can anyone recommend some straightforward, reliable hardware that's already set up like that, that I can just buy?

  • 1
    You don't need hardware, assuming you already have the teaching setup specified; all you need is software. Something like Voicemeeter Banana for Windows or Audio Hijack for Mac. – Tetsujin Mar 11 '18 at 8:55
  • Yes, voicemeeter, I was going to suggest that as well. Never used it but believe you can also multi track from it. – Timinycricket Mar 11 '18 at 10:04
  • @Tetsujin Like I said, I'm stuck with pulseaudio on linux. – Owen_R Mar 11 '18 at 10:11
  • 1
    Presumably there's something similar for nix, though it's one platform I know very little about. – Tetsujin Mar 11 '18 at 10:14
  • A stereo recorder should be the simplest way if you just get a 'Y' splitter and plug one source into the right and the other source into the left. They generally will have an output jack as well that you can monitor from. – Timinycricket Mar 15 '18 at 4:24
1

On Linux, you can use the Ardour DAW, it will record the separate tracks synced to it's internal software time-code.

It should be trivial to route the audio from skype into Ardour using Pulseaudio (it might be easier with Jack Audio) as well as the digital signal from your mic.

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