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: William Stewart <email@hidden>
- Date: Fri, 27 Jan 2006 12:07:49 -0800
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
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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