Re: AU "offline" processing
Re: AU "offline" processing
- Subject: Re: AU "offline" processing
- From: Alberto Ricci <email@hidden>
- Date: Fri, 31 Jan 2003 15:53:53 +0100
At 9:22 AM -0500 1/31/03, Marc Poirier wrote:
but the practical question is: will music host apps tolerate
this and make sure that the correct behaviour happens? Is there a good
way to inform the host of these special needs?
Exactly. Suppose we have a random access "read samples" host
callback. Suppose we're time compressing. Such an AU would probably
read samples in chunks, when a chunk is complete it processes it and
outputs a smaller number of samples (because we're time compressing).
And so on.
How would the AU tell the host when it's done processing? Would the
host be expecting as many samples out as it sent into the AU?
Since CoreAudio is based on a pull mechanism, it's up to the host to
decide when to stop pulling for samples. It could stop after the AU
has processed a given number of samples, unless it starts returning
null buffers before that time.
But what if we're time expanding? The host starts pulling for
samples, receives a number of samples equal to the number of selected
samples in the editor, and how can it know that is should keep
pulling for samples because there are a lot more to come? Should it
pull until it receives null buffers, no matter what?
Maybe all the functionality is already present in CoreAudio. I am not
sure I grasped the concept in its entirety, though.
Alberto.
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