GarageBand Sample Rate Problems w/ mBox

[nikomatsakis]

I am trying to record using GarageBand with my mBox; I've found garageband to be
easier to use than ProTools for the simple recording I'm trying to do.

Now, this used to work fine, but I took a break for a few months and in the interim
something changed and now it doesn't well at all.

Specifically, when I record using the mBox, the resulting waveform appears fine
in the GarageBand viewing window until I stop recording; at this point the waveform
compresses to about a tenth of its original width. When I try to playback what I
recorded, I get a "squished up" version that plays extremely fast and choppy, so you
can barely understand it at all.

Someone from apple suggested that perhaps the sample rate was being miscommunicated
between the two programs (garageband and coreaudio), but everything appears to be
operating at 44.1kHz; in fact, if I try changing the sample rate on CoreAudio, it reverts to
44.1kHz when I start GarageBand.

ProTools seems to be able to record without trouble and everything plays back normally.
GarageBand works fine when using the internal microphone.

Any clues? I am very frustrated.

I am using Mac OS X 10.3.4, CoreAudio 6.5.4, GarageBand 1.1.0, and I don't
know if the mBox has a version number but I bought if a few years ago (2? 3?).

Oh yeah, and I tried trashing the preferences for everything coreaudio related, as well
as reinstalling the most recent version I could find, and trashing any garageband prefs.
No dice.


Niko

[Digi Engineering]

Sounds like a buffer-size mismatch between GB and the CoreAudio driver.

Open the "Audio/MIDI" pane in the GB Preferences, and toggle the "Optimize For" radio buttons. This should get GB to re-sync it's buffer size to what the CoreAudio driver is using.

-Ted

DAE Group
Digi Engineering

[nikomatsakis]

Okay, you're on to something here. When I toggle the buffer settings,
it seems like the driver is using the larger buffer setting no matter what GB
says and I can get undistorted sound. However, the recording seems to
have a 3 measure, or 4.5 sec, delay (descibed in detail below).

More details:

With the "large" buffer setting:

The good news is that I got it to actually record sound that did not playback
distorted. Unfortunately, it seems to take a while to start recording: I thought
this might be "Count-In", but that is not enabled. Anyhow, while it says its
recording, it's not till about 3 measures in (approx 4.5 sec) that the
sound starts to get recorded.

This might be tolerable, except that the words I have been recording are
then shifted back to the place where I began recording, only with the first few
words cut off.

So when recording, if I said "A B C D E F" then the waveform wouldn't start
recording till about "D" (i.e., you would see " D E F"). Once I finished recording,
it would get shifted and it would seem as though I just said "D E F".

With the "small" buffer setting:

Nearly the same behavior, except that the compression effect happens as well.
So perhaps the driver is set to the larger buffer setting permanently, and GB
can't affect it.

Either way, I still get the same "4.5 second" delay when I record.

[Digi Engineering]

That 4.5 second delay sounds like a GB issue, not a driver issue. That's way too long to be related to the buffer-size.

If you make the Digi CoreAudio Manager app visible, you can see the current buffer-size that it's set to. I just tried toggling the radio buttons in GB, and the CoreAudio driver changes it's buffer-size accordingly.

-Ted
DAE Group
Digi Engineering

[nikomatsakis]

Well, I this is progress anyhow. I'll see if Apple can figure out the 4.5
second delays. Regarding the buffer size: when I toggle the buffer size,
it seems to have no effect on the selected buffer size in the driver window.
I looked for that specifically. I believe it always says "512" (I am not in front
of it right now)