Re: Accessing underlying AUGraph being used by quicktime
Re: Accessing underlying AUGraph being used by quicktime
- Subject: Re: Accessing underlying AUGraph being used by quicktime
- From: Craig Hansen-Sturm <email@hidden>
- Date: Fri, 27 Jan 2006 16:15:33 -0800
On Jan 27, 2006, at 12:07 PM, William Stewart wrote:
On 26/01/2006, at 12:44 PM, Brian Sheehan wrote:
Craig,
I'm just learning the CoreAudio API at the moment, and I'm still
trying to get my head around what's doable or not. So just to
confirm,
are you saying that the AUs used/instantiated through the quicktime
api can not be accessed in any way?
Yes, whatever QT is doing to render audio is private implementation
with no public interface at this time.
I think it is more productive to go back to the original problem -
what is it that you want/need to do (and describe this from the
point of view of tasks, rather than ideas about how you would
"ideally or otherwise" implement it)
Thanks
Bill
Bill is definately going to kill me for even mentioning this.
But.... ;-)
....There are ways of using the QuickTime Component Manager api's to
"capture" system components (AU's are, of course, just generic qt
components). There are also debug-helper api's which can be used
to walk internal process data-structures. However, none of this is
supported, and it is definately not recommended practice. I would
not consider using these facilities for any shipping product.
cheers.
--craig
I suppose more generally I'd be interested to know if there was a way
of accessing an AUGraph or standalone AudioUnit that you didn't
have a
reference for. For example, accessing the AudioUnit instances of
other
running applications.
thanks for your help,
Brian
On 1/26/06, Craig Hansen-Sturm <email@hidden> wrote:
Brian,
QuickTime audio is making use of many of the standard AU's, the
AudioConverter, and the OutputUnit.
However, the infrastructure to "wire" these units together is opaque
currently, and is not based on
AU Graphs.
At the time of the design, we were unclear whether there was
sufficient interest from 3rd parties to provide
an external API. I believe this wouldn't be difficult to do;
however.
--craig
On Jan 26, 2006, at 10:39 AM, Brian Sheehan wrote:
Thanks for your response Brad.
That's strange, cos the docs hint at some sort of facility for
doing this:
"If you need to work with QuickTime at a lower level, to modify
individual video frames during playback, for example, or to add a
filter to the sound output, you need to work with the underlying
technology that QuickTime relies on for output. This will vary
depending on your platform and software revision.
For example, QuickTime 7 for Mac OS X uses Core Audio for audio
output. To work with QuickTime audio at the low level, you
should use
the Core Audio API. Older versions of QuickTime send audio
output to
the Sound Manager (included in QuickTime for Windows). To work with
low level audio on these systems, you need to use the Sound Manager
API."
What part of the Coreaudio does Quicktime use? Anything I can
get my
hands on at all?
thanks again,
Brian
On 1/26/06, Brad Ford <email@hidden> wrote:
On Jan 26, 2006, at 10:15 AM, Brian Sheehan wrote:
Hi,
The quicktime docs make a passing reference to this
(http://developer.apple.com/documentation/QuickTime/RM/
Fundamentals/
QTOverview/index.html),
so it should be possible - how would I go about getting a
reference to
the AUGraph that is being used during playback of a movie
using the
Quicktime API?
This is quite impossible as QuickTime doesn't use AUGraph to play
back audio.
Just to give an idea of what sort of situation this might be used
in -
I want to use quicktime to playback a movie, but I want to filter
the
audio output through some AudioUnit.
This is currently not possible through public API. Sorry.
-Brad Ford
QuickTime Engineering
thanks,
Brian
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