auval and you
auval and you
- Subject: auval and you
- From: William Stewart <email@hidden>
- Date: Tue, 20 Mar 2007 11:44:31 -0700
As many of you know, audio units are plugins that run within the
process (address space) of a host application. They enhance the
capabilities of the host apps, providing many choices to users for
synthesis, sampling, audio processing and so forth.
From the perspective of a host app, there are two primary conditions
that must be met:
(1) The API as specified for the audio unit must be implemented
correctly
(2) The behaviour of the audio unit must be predictable and reliable.
If these two criteria are not met the user can experience
instabilities when using the audio unit within a host application
(such as Logic, Garage Band, Digital Performer, etc), including
catastrophic consequences such as crashing and the loss of unsaved data.
auval is a tool that was designed to validate the basic behaviour and
operation of an audio unit. Its primary focus applies to two areas:
(1) API conformance/correctness
- does the audio unit implement the semantics of the API contract
correctly?
(2) Behaviour
- does the audio unit have bugs that would cause random crashes or
other undesired consequences?
An audio unit passed through the validation process can have several
results:
(1) PASS
- the API is implemented correctly and no problems have been detected
(2) PASS with warnings
- the audio unit may have some problems in some situations, but in
general it is behaving correctly
In the following two cases the audio unit should be considered to be
unreliable and problematic if used:
(3) FAIL with errors
- the audio unit exhibits some significant problems that would
impact its general usability
(4) Crashes
- in some cases the auval tool is not able to directly detect a
problem with the audio unit, but it can cause something bad to happen
in the audio unit through the testing that it does.
Regardless of any of these results, auval has no actual influence or
affect on the audio unit when it is used within a host app.
The primary API specification for audio units was described with Mac
OS X 10.2; it is known colloquially as "Audio Unit v2"; version two
of the API. The API calls are expressed primarily in the
AudioUnit.framework, in the header files AUComponent.h and
AudioUnitProperties.h. Audio units have of course developed since
then, with new features added to accommodate different scenarios and
user requirements, however the basic API semantic and compatibility
has remained as defined at that time.
The auval tool has also developed since then; it has changed to test
and validate new features and is also able to detect problems now
that it previously wasn't able to. We regularly seed copies of auval
to all audio unit developers to ensure that the auval tool is not
itself introducing problems as well as to provide a chance for
feedback and other comments. We seed as often as we can; providing
builds months ahead of when we would expect these to be released to
the general public. We expect developers, just as our users expect
this of us, to incorporate fixes to these problems in their updates,
hopefully before a new version auval itself is released.
As an example of this, the changes that were made to auval as
released in 10.4.9 were largely made and seeded to developers in Sept/
Oct 2006 (some of these changes even earlier than this). We also
disabled some of the tests as they would apply to a Tiger based
system because we didn't think they warranted a failure on such a
system. In these cases, they will however fail when running against
the auval installed with a Leopard system; this version has also been
seeded to developers.
If you are not on the auval seeding program and you are developing
audio units, then please contact me (William Stewart: email@hidden).
We'll gladly answer any comments or concerns.
Thanks
Bill
--
mailto:email@hidden
tel: +1 408 974 4056
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"Much human ingenuity has gone into finding the ultimate Before.
The current state of knowledge can be summarized thus:
In the beginning, there was nothing, which exploded" - Terry Pratchett
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