Audacity Forum

The stereo guitar sound from my Focusrite sound card is going via firewire then thunderbolt adapter into my Mac. It appears for some reason on inputs 5 & 6 of Audacity. However Audacity won't let me select 5 & 6 as inputs. When I select for example input 6 & record. I get 6 tracks appear (1 to 6) with my guitar sound on the bottom two (5&6).
I obviously only want two tracks for stereo guitar. So how can I achieve this without also getting tracks 1 to 4 on screen ?
Ideally if I could get the focusrite to send to tracks 1 & 2 of Audacity so I can then select that input as 1/2 stereo but how can I achieve this ?
Thanks

Pobinr wrote:I obviously only want two tracks for stereo guitar. So how can I achieve this without also getting tracks 1 to 4 on screen ?

Only by using inputs 1 and 2 of the sound card. Audacity does not yet have channel mapping to make inputs 5 and 6 appear as channels 1 and 2 in Audacity.

If inputs 1 and 2 are not suitable, then use the first two channels that are suitable, record as many tracks as required, then delete the empty tracks when the recording is stopped (Click the [X] in the top left corner of the track to delete the track).

Thanks I see that's what I'll have to do & delete tracks 1 to 4 each time!
Focusrite support suggested getting Logic software where routing of inputs is possible. It's a shame as I love Audacity, but not quite able to do what I now need to.

The real problem is that Windows sound card drivers do not support channel mapping. Most other recording applications get round the problem by using ASIO drivers (which do support channel mapping), but Audacity cannot be distributed with ASIO support because of a conflict between the open source license of Audacity and the closed source license (non-free) of ASIO.

You probably don't need to specifically use Logic for recording. Any recording program that supports ASIO should work. Some low cost or free programs that you could try include: Reaper, Wavosaur, Kristal Audio Engine.

If you prefer editing in Audacity, you could always use another program for recording, then export the recording as a WAV file, then edit the WAV file in Audacity.

steve wrote:The real problem is that Windows sound card drivers do not support channel mapping.

We're on Mac here, hence OP can record six consecutive channels rather than from one of three different stereo pairs as happens on Windows, but cannot choose the required channels from the six available.

Does ASIO on Windows let you choose which of multiple channels to record? I may be wrong but I thought that issue was down to Audacity whatever the OS.


Gale

I suspect it's down to Audacity. I hope one day they programme Audacity to enable re routing of inputs or presumably be able to select tracks to not be active. In my case tracks 1 - 4. One would think not that hard to achieve. But that all takes time & it's free.

Gale Andrews wrote:We're on Mac here

Oops

Gale Andrews wrote:Does ASIO on Windows let you choose which of multiple channels to record?

Usually yes. I don't know if that is always the case, but for example, if using ASIO4All, once it has been enabled in the audio application, the ASIO4All control panel becomes available through which you can configure which devices and in/outs you wish to use.

On Linux you can do a similar thing with Jack.

Is there no way to do that on Mac?

Well I have a humble request for Audacity developers. Please could we have the the option to re-route or select precise inputs to Audacity to get round this problem. Thank you in anticipation

steve wrote:I don't know if that is always the case, but for example, if using ASIO4All, once it has been enabled in the audio application, the ASIO4All control panel becomes available through which you can configure which devices and in/outs you wish to use.

OK, but that's like using an external channel mapper, then? And if you can choose for example channel 5 and 6 only in the ASIO control panel, does choosing "2 (stereo) input channels" in Audacity Device Toolbar then let your record only channels 5 and 6?

Someone has just told me that scenario still records silent channels 1 and 2 on his self-compiled ASIO build of Audacity. So perhaps a lot may still depend on the actual audio device?

steve wrote:On Linux you can do a similar thing with Jack.

So again how does that work in Audacity in the above scenario?

steve wrote:Is there no way to do that on Mac?

CoreAudio should support multi-channel recording on most devices. I don't know any formal way it has to do channel mapping, unless Apple Audio MIDI Setup provides that for a multi-channel device. Have you looked there, Pobinr?

Also there is Jack OS X .

Pobinr wrote:Please could we have the the option to re-route or select precise inputs to Audacity to get round this problem.

I've already made a note to add your vote for this

If you want to try compiling Audacity then there is a patch here that uses "Recording Profiles" set in audacity.cfg to choose the channels to record and what tracks to record them to.

There is no way to make these settings in the interface yet, and unfortunately the developer who was working on this has no time to pursue it right now.

However if you reply to the topic that patch is in, the developer may see it and be encouraged...


Gale

Gale Andrews wrote:OK, but that's like using an external channel mapper, then?

In part yes, but I don't think that it can (for example) be used to set input 2 to channel 1 and input 1 to channel 2. It just selects which inputs are enabled.

Gale Andrews wrote:And if you can choose for example channel 5 and 6 only in the ASIO control panel, does choosing "2 (stereo) input channels" in Audacity Device Toolbar then let your record only channels 5 and 6?

I don't have a multi-channel sound card or an ASIO enabled build of Audacity to test that, but I would expect that is what "should" happen.

Gale Andrews wrote:Someone has just told me that scenario still records silent channels 1 and 2 on his self-compiled ASIO build of Audacity.

Either I'm wrong about what should happen (though that is what appears to happen in ASIO enabled applications, and it makes sense),
or they do not have ASIO/Audacity set up right,
or Audacity does not do the right thing with ASIO (I'd not be surprised if the situation were similar to the case with Jack, as described below).

Gale Andrews wrote:

On Linux you can do a similar thing with Jack.

So again how does that work in Audacity in the above scenario?

When a multi-channel device is selected as the input for Jack, the device is seen as a "readable client" and each input appears as a "socket".
Audacity does not handle this correctly, so here's what "should" happen, what "does happen, and two workarounds for Audacity's incorrect behaviour:

What should happen:
The required inputs would be selected by the users in the audio application (this is limited in Audacity to the number of channels rather than which channels).
Recording would then connect to those selected channels.

What does happen:
If, for example, 3 channels are selected, Audacity connects to channels 1, 2 and 3, regardless of any settings in Jack.

Workaround 1:
Set Audacity to use the number of required inputs.
Put Audacity is "Record/Pause" mode.
Switch the inputs that Audacity is connected to using the "Connect" utility in Jack Control, (or whatever your preferred Jack configuration tool).
The downside of this workaround is that you need to redo the connections every time that you want to record. Audacity defaults to the first n channels each time that you start recording or monitoring.

Workaround 2:
Start Jack, and open a "dummy" jack application that has inputs straight through to its outputs (for example an empty instance of JackRack.
Connect the "dummy" application to the required input ports (for example, inputs 4 and 2). "System ports" 4 and 2 are now connected to inputs 1 and 2 of the "dummy", and thus to outputs 1 and 2 of the "dummy".
Start Audacity and set it to record 2 channels from the "dummy".
Press record, and Audacity will record channels 1 and 2 from the "dummy", which are directly connected to system ports 4 and 2, so Audacity records "input 4" from the audio device on channel 1 and "input 2" from the audio device on channel 2.
In effect the channel mapping is being handled externally to Audacity.

Gale Andrews wrote:If you want to try compiling Audacity then there is a patch here that uses "Recording Profiles" set in audacity.cfg to choose the channels to record and what tracks to record them to.

That is looking promising, and will hopefully enable Audacity to work correctly with Jack and other multi-channel systems in the future.