Re: TransportState AU host callbacks - Logic warning
Re: TransportState AU host callbacks - Logic warning
- Subject: Re: TransportState AU host callbacks - Logic warning
- From: William Stewart <email@hidden>
- Date: Tue, 30 Mar 2004 10:18:31 -0800
Thanks for the report Marc,
I forwarded your comments onto Emagic and they will have this fix in
their next update - no, I don't know when this will be... This will
also be the same problem in Garage Band (but they have fixed it there
now as well). They are also working on providing the implementation for
this, but I don't know when they'd have that available...
Bill
On 28/03/2004, at 1:19 PM, Marc Poirier wrote:
>
Warning: For those of you experimenting with supporting the new
>
TransportState AU host callbacks, beware that your plugin will crash in
>
Logic. Unfortunately, given the way Logic is behaving right now, you
>
simply can't even try using the callback if anyone might use your
>
plugin
>
in Logic.
>
>
The bug is that Logic, when Setting the
>
kAudioUnitProperty_HostCallbacks,
>
is providing a bogus value for the inDataSize parameter. It is telling
>
the AU what it thinks the AU wants to hear rather than the actual size
>
of
>
the incoming data buffer, i.e. it is passing the value received from
>
GetPropertyInfo rather than the size of the actual data being offered
>
to
>
the AU. So the problem with this is that, the buffer that Logic is
>
passing is 12 bytes in size, but it is telling the AU that it is 16
>
bytes,
>
and so the AU reads in 4 bytes of random garbage as the value for the
>
transportStateProc function pointer.
>
>
This whole system is supposed to be designed in a way such that the
>
host
>
callbacks structure can be extended and older hosts will still safeul
>
work
>
with newer plugs, but when hosts do things incorrectly in this way,
>
unfortunately it makes it unsafe to do what you ought to be able to do
>
safely.
>
>
So hopefully Emagic will fix this soon. This is a really big problem!
>
Given how popular of an AU host Logic is, this effectively means that
>
no
>
one can make use of the new callbacks until Logic is fixed. :-(
>
>
I'm going to report this to Emagic now, but I thought I'd put a warning
>
out to other AU developers, too...
>
>
Marc
>
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