Re: Did GarageBand stop playing?
Re: Did GarageBand stop playing?
- Subject: Re: Did GarageBand stop playing?
- From: "Daniel Jalkut" <email@hidden>
- Date: Thu, 26 Jan 2006 06:00:31 -0800 (PST)
- Importance: Normal
Thanks for clarifying, Bill. I definitely misunderstood about when I could
call the host callbacks, so you've surely saved me some grief. I will try
them out and see if they do the trick in GarageBand!
Daniel
>
> 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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