Re: Trying to port my app to Core Audio. Audio Sync
Re: Trying to port my app to Core Audio. Audio Sync
- Subject: Re: Trying to port my app to Core Audio. Audio Sync
- From: James McCartney <email@hidden>
- Date: Mon, 2 Feb 2004 18:01:27 -0800
On Feb 2, 2004, at 5:36 PM, Ralph Hill wrote:
I have no strong reason to not use the output audio unit. But I don't
see any advantage to the output audio unit. I looks to me like I have
the same three issues with the output audio unit that I have with the
HAL:
1. I have to add a ring buffer to match a push model application to a
pull model library.
2. I have to force the pull model library to use small buffers
(~10msec)
10 milliseconds is not small.
Anyway this doesn't make much sense. You can either have a push model
or low latency. Choose one or the other. Only the hardware knows where
it is in the data and the HAL has sophisticated clock algorithms for
chasing it. If your software wants to push however much it wants
whenever it wants as you stated, then you will not do as well. Pushing
is great for things like playback of pretimed or prerendered data. But
if you need low latency then pushing is not the best model.
3. I have to have a way of estimating when the sound gets to the
output jacks.
Is it easier to do these three things in the output audio unit than
the HAL? I have looked and I don't see an easier way than for the
HAL. Can you suggest an way to use the audio output unit to get what
I need?
Yes you still need a pull model.
The output unit does a lot of other work automatically tracking the
hardware state for you which you will have to do if you use the HAL.
-
james mccartney
apple coreaudio
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