Re: Transport start/stop for Effect Units needed
Re: Transport start/stop for Effect Units needed
- Subject: Re: Transport start/stop for Effect Units needed
- From: Chris Rogers <email@hidden>
- Date: Thu, 15 May 2003 11:03:11 -0700
Paul,
What type of action are you wanting to do in an AudioUnit effect
which relies on knowing exactly when the transport starts?
We already have AudioUnitReset() which hosts should be calling
in most conditions before the transport is started.
AudioUnitReset() is designed to allow the AudioUnit to reset
its internal state, clearing filter memory, delay buffers, etc.
I'm just curious to know what specific types of operations you
need to do in the AudioUnit at this time and if it's somehow
separate from our concept of "reset"
Chris Rogers
Core Audio
Apple Computer
Chris Reed <email@hidden> wrote:
Couldn't you use the current host time and beat location callback to
determine if playback is progressing? If the current location doesn't
change, or the host returns an error for that call, then you can assume
the transport is stopped.
That is ok (as Howard says - if you can rely on the reported location)
but watching to see if the current location is changing isn't always
good enough. If the transport is stopped at the start of bar 1, then
starts playing *from there*, the start location for each frame will be
something like:
1.000 transport is stopped
1.000
1.000
1.000
transport starts
1.000
1.003 <- you detect the location is now changing
1.006
So you missed the opportunity to do something exactly on the first beat
of the bar! This is really a problem when the user wants to select an
exact range and render the plug-in output to a file.
Paul.
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