Re: AU - does Latency imply equal TailTime?
Re: AU - does Latency imply equal TailTime?
- Subject: Re: AU - does Latency imply equal TailTime?
- From: Alan Cannistraro <email@hidden>
- Date: Wed, 29 Jan 2003 01:16:49 -0800
K,
I think your assumptions are correct. We only set
kAudioUnitProperty_Latency for our plug that adds a delay to the input
- everything works as expected (hosts compensate for the delay
properly). I think kAudioUnitProperty_TailTime would be used in the
case of a reverb or some such that does not in fact delay the audio
but does add length to it.
This is one way to look at it, but it should not be limited to just
adding length to the end of a clip. As per Chris's explanation, it
also incorporates the impulse response of the filter. If a low-pass
filter requires n-samples to reach steady-state, then it is important
to report the time period of those n-samples as the tail time. Some
applications may wish to use this to achieve seamless bounces to disk,
so that a bounce from the beginning of a composition would yield
identical results to seaming two consecutive bounces of half the length
of the composition. In other words, the low-pass filter described
above would need n-samples before time zero in order for the sample at
time zero to be correct.
Al
On Tuesday, January 28, 2003, at 03:13 PM, Marc Poirier wrote:
Does a value for the kAudioUnitProperty_Latency property imply that,
at
the end of the input signal, there will still be output for an equal
amount of time? Or is an Audio Unit expected to return that same
value
for the kAudioUnitProperty_TailTime property in such a case? To me,
latency means latency all the way through: it starts late and it ends
late. And then if there is an additional tail on top of the already
expected delay (from the latency), then that additional value would be
returned from the kAudioUnitProperty_TailTime property.
Are my assumptions correct, or should AUs add the Latency into the
TailSize?
Thanks,
Marc
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