Re: Q: Setting the size of an AudioUnit buffer?
Re: Q: Setting the size of an AudioUnit buffer?
- Subject: Re: Q: Setting the size of an AudioUnit buffer?
- From: William Stewart <email@hidden>
- Date: Fri, 6 Feb 2004 10:02:44 -0800
On 06/02/2004, at 12:34 AM, A. Le Flanchec wrote:
Hello,
I also have a problem with that. I tried to set the
MaximumFramesPerSlice property (up to 65536), but it did not change
ioNumberDataPackets (in the example PlayAudioFileLite, as far as I
remember) which is still set at 512. Maybe I'm doing something
wrong... I used kAudioUnitScope_Global... is it right to do so ?
Max Frames just describes to the AU what the maximum (and we would hope
normal and only!) number of frames that you are going to ask an AU to
do at any time... The AU then knows how much memory to allocate for
buffers (like delay lines, etc...)
It has *nothing* to do with the actual number of frames of the render
call.
If you are talking to an Output AU that is talking to a device (like
the AUHAL or Default Output units), then the actual number of frames
that the AU is going to render is determined by the device's I/O proc's
frame count (see <CoreAudio/AudioHardware.h>
By the way, I am completely new to making audio apps. I'm stuck in the
middle of a VERY steeeep learning curve, if you see what I mean... I
think that I should use different threads for the audio rendering and
the GUI. Maybe the fact that we hear drops while playing a file with
'PlayAudioFileLite' is also related to the fact that there are no
separate threads ? What do you think ? Is it necessary to use separate
threads with different priorities to make a rock solid audio app ?
Different threads for the MIDI and the Audio side ?
The much vaunted, and soon to come next rev of the SDK has some
completely rewritten audio file playing and recording code that I think
will help alot
Bill
OK, these are very basic questions... but I really would appreciate
some help, before I completely despair !
Vince
Subject: Re: Q: Setting the size of an AudioUnit buffer? To: Lance
Drake <email@hidden>
F>rom: Marc Poirier <email@hidden>
Date: Sun, 1 Feb 2004 14:24:44 -0600 (CST)
You want to set the MaximumFramesPerSlice property (or maybe it's
called MaxFramesPerSlice, but whatever, that's the one).
Marc
On Fri, 30 Jan 2004, Lance Drake wrote:
Hi Core-Audio folks,
After pouring thru the online literature, reading the
CoreAudio.pdf and scanning thru the headers, I have still not
determined how to set the size of the AudioUnit buffer - or where the
default value of 512-packets comes from.
As it is, my chore of reading a file to audio is grabbing 512
packets at a clip via the 'ioNumberDataPackets' quantity sent to my
inputProcessor routine as setup by the call to
AudioConverterFillComplexBuffer which is getting this number from the
render process specified by the call to AudioUnitSetProperty where
the property is kAudioUnitProperty_SetRenderCallback.
The solution (I imagine) is to also make a call to
AudioUnitSetProperty with the property of
kAudioUnitProperty_SetExternalBuffer - but what args I should send in
with that call.
The net result is what sounds like halting audio output that
seems to be a result of the buffer being starved because the OS is
off doing other things. My thought was that if I use a larger
buffer, this negative effect would be eliminated.
Thanks for your assistance,
Lance Drake
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