Re: Problems setting sample rate
Re: Problems setting sample rate
- Subject: Re: Problems setting sample rate
- From: email@hidden
- Date: Thu, 18 May 2006 17:09:57 -0400
Hi Ted,
Thanks for all of the great info!
Currently, my host (client app in your terms) does not have a sample
rate menu. I'm not trying to change the sample rate. So, by default
everything is running at 44.1 kHz, and my app works fine with the Mbox
if the SR is set to 44.1k. However, the Digi CoreAudio Manager app
allows the user to set the sample rate of the Mbox to 48k if no other
clients are using it (under the Advanced menu button). After that, I
launch my client app, and I'm just trying to make it play correctly at 48k.
- Rick
Ted Barram wrote:
Hi Rick –
Since our CoreAudio driver is a user-space plugin rather than a kext,
there are some limitations that we imposed on it to make it play better
with client apps. One thing we did was to only allow the sample rate and
buffer-size to be changed by a client if that client is the only one
connected to the Server (aka Manager app). We did this for buffer-size
changes because our user-space model doesn’t support different clients
running at different buffer-sizes, and we encountered some clients that
were not listening for a “buffer-size changed” notification, which would
cause them to crash when another client changed the buffer-size. We saw
the same thing for sample rate changes, albeit not a crash, just
slow/fast audio. So, although these are actually client app bugs, we
opted to insulate ourselves against them. This decision is probably
worth revisiting on our end, especially the sr part.
So, if there’s more than 1 client attached to the Server/Manager, then
you can’t change the sr.
Also, the Manager app is not really a control panel, it’s an actual
server app that allows multiple clients to stream audio to our hardware.
When it’s launched, it owns our hardware, and PT can’t use our HW, so we
take pains to only launch it when it’s really needed. This is one reason
why it’s not published as the official control panel for our device.
One more thing: The Mbox2 uses a native IOKit-based driver, so it
doesn’t need the Server/Manager app (and all its associated baggage).
Hallelujah.
Hope this helps,
-Ted
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