Re: Did GarageBand stop playing?
Re: Did GarageBand stop playing?
- Subject: Re: Did GarageBand stop playing?
- From: William Stewart <email@hidden>
- Date: Wed, 25 Jan 2006 19:23:54 -0800
On 24/01/2006, at 9:25 AM, Daniel Jalkut wrote:
Thanks, kelly. (And others who replied!)
I'm glad to know I wasn't just missing something obvious. I will
look into the GetTransportState option, but I guess I would still
have to install some kind of timer to periodically call through to
the host.
Nope.
Please read this carefully.
The Host callbacks are ONLY VALID if called from and AudioUnit's
render call. You cannot set up a timer and periodically "poll" the
host. If the host is not calling your AU's render call, then of
course you aren't being asked to render. You also cannot just call
the Host callbacks to find out if the host's transport is running or
not.
This is quite a deliberate decision on our part = the intention of
the host callbacks is to provide additional information to the AU
about the time as it relates to the current render operation.
So, the correct way for you to ascertain if the host's transport is
running is as Kelly described.
Bill
Maybe support for this will improve as "generator" type instruments
become more prevalent. I tried to look to AUFilePlayer as a
possible example, but it doesn't seem to be well-supported in
GarageBand 2.0. (I am waiting for my Intel Mac to bring new
GarageBand goodness).
Daniel
On Jan 24, 2006, at 9:47 AM, kelly jacklin wrote:
Hey Daniel,
Check out HostCallback_GetTransportState in AudioUnitProperties.h
and here:
<file:///Developer/Examples/CoreAudio/Documentation/AudioUnits/
Topics/au_properties.html#HostCallbacks-MusicalTime>
It has a boolean indicating whether or not the transport is
currently running. I do not know for sure whether GB supports
this currently, but what you want is what it's intended for, so
it's worth a try.
I know there have been issues in the past with Logic incorrectly
filling in the HostCallbackInfo structure with garbage for the
callbacks it didn't know about (which this one is), but I do not
know if this applies to GB. See the archives for (IIRC) Marc
Poirier's excellent discussion of how to detect whether you can
trust this callback when running under Logic, and indeed how to
detect if you are running under Logic to know whether you need to
worry about it. This may all be moot nowadays, or you may not
care if this is just for your own use in GB...
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