Re: Sample-accurate parameter automation? Possibe at all with AUs?
Re: Sample-accurate parameter automation? Possibe at all with AUs?
- Subject: Re: Sample-accurate parameter automation? Possibe at all with AUs?
- From: William Stewart <email@hidden>
- Date: Tue, 11 Mar 2008 16:09:52 -0700
Yes. And Stephen's general description is right..
As for a stream of parameter events... we had this notion in general
sometime ago and we even defined in specific format type for this kind
of control stream (see CoreAudio/CoreAudioTypes.h)
However, there didn't seem to be a general interest in providing a
sample by sample parameter stream, so we've basically not done
anything further on it.
Audio units in general are pretty agnostic about what format they see
on given buses, so its something we could add if there was sufficient
interest from both AU and host app developers
Bill
On Mar 11, 2008, at 3:15 PM, Brian Willoughby wrote:
On Mar 11, 2008, at 15:06, Kevin Dixon wrote:
The answer lies in the source code for AUBase and AUEffectBase, or
perhaps some of the others. I believe it is AUEffectBase which has
optional code to split the render process into chunks. Without
sample-accurate parameters, you always get a full buffer and process
it at once. But with sample-accurate parameter scheduling,
AUEffectBase will calculate the points within the buffer where the
parameter value changes to a new value. Then, your normal render
will be called with a small chunk of the buffer, just the part where
the parameter remains constant. In this case, you still just call
GetParameter once at the beginning of your render, but you'll be
called again to render the next parameter value.
So given this information, if an AU inherits from AUEffectBase,
then as a
host, you could schedule parameter changes and then by calling
render, it
would take care of itself by splitting the render up at the scheduled
points?
-Kevin
I believe the answer is 'yes'
I also think you have phrased the question perfectly. i.e. it seems
to be the responsibility of the AU to handle breaking down buffers
for sample-accurate parameters. Unless I'm wrong, the AU Host is
apparently only required to provide the information necessary, but
not to actually break down the buffers or anything like that.
Brian Willoughby
Sound Consulting
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