Re: Updating AUBD on the fly...
Re: Updating AUBD on the fly...
- Subject: Re: Updating AUBD on the fly...
- From: William Stewart <email@hidden>
- Date: Thu, 23 Mar 2006 11:03:14 -0800
On 23/03/2006, at 10:09 AM, Mark Coniglio wrote:
I am receiving an kAudioUnitErr_PropertyNotWritable error when
attempting to change the ASBD of an AUAudioFilePlayer when the
AUGraph that contains it is running.
More correctly, you will be getting this error because the AU is
Initialised, and it is rejecting a format change while it is in that
state.
I would like to know if it is possible to set the ASBD of a non-
playing AUAudioFilePlayer within a running AUGraph. Obviously I can
restart the graph, but this causes other files that are currently
playing to start over from the beginning.
This issue is discussed in the AU Docs (formats and Initialised state).
Bill
Background:
In my program, the user can change the audio file being played by a
AUAudioFilePlayer while the graph is running. Each file player has
an AUConverter between its output and the next input, so that I can
standardize number of inputs, sample rate, number of channels, etc.
Before attempting to change the files, I do the following:
- Stop playing the current file by calling AudioUnitReset on the
AUAudioFilePlayer's output
- Call AudioUnitReset on the input to the AUConverter
- Call AudioFileClose on the output of the AUAudioFilePlayer
Then I start initializing the AUAudioFilePlayer to play the new file.
The problem occurs when the user switches from a stereo to a mono
file. In this case, I am attempting to set the output format of the
AUAudioFilePlayer, by changing the mChannelsPerFrame from 2 to 1.
Then I call
AudioUnitSetProperty(audioUnit, kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output, 0, &auFormat, propSize);
This exact same code works when after calling AUGraphOpen but
before any connections are made, and before calling
AUGraphInitialize and AUGraphStart.
It does not work if the graph is running, even if I disconnect all
of the inputs and outputs to the AUAudioFilePlayer and AUConverter
and reset them both.
Any ideas?
Best Wishes,
Mark
--
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Mark Coniglio, Artistic Co-Director | email@hidden
Troika Ranch Dance Theater | http://www.troikaranch.org
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