Re: Audio File to PCM Float32 Format Converter?
Re: Audio File to PCM Float32 Format Converter?
- Subject: Re: Audio File to PCM Float32 Format Converter?
- From: William Stewart <email@hidden>
- Date: Mon, 9 Jan 2006 11:14:22 -0800
See the PlayFile example in the latest SDK - it uses the AUFilePlayer
(a generator type of AU 'augn')
On 08/01/2006, at 5:42 PM, Puhl, Scott wrote:
I'm needing an Audio Unit that reads from an audio file and renders
PCM Float32 data.
Before I write this myself, I want to find out if its already
available to me.
It seems it may be, as alluded in the Audio Unit API Documentation
(Developer/Examples/CoreAudio/Documentation/AudioUnits/Topics/
au_type.html):
"Format Converter Units
Typically, Audio Units deal with PCM data in Float32. However,
several format conversions may
be desirable within a processing chain, such as the source of a
chain that supplies data from a file, sample rate conversion..."
Is a format converter unit provided that does this?
aufc, conv, appl
The difference between a format converter AU and a file player AU
(which is a generator AU) is that an aufc is converting its input to
its output. An aufc has a relaxed semantic about the relationship
between input and output - it can ask for more or less data as
necessary for instance.
A generator has no input elements, but rather just outputs; how a
generator generates its audio data is internal and opaque to the user
of the AU.
As a second question, is the subtype functionality for the Apple
format converter units documented anywhere?
kAudioUnitSubType_AUConverter = 'conv',
kAudioUnitSubType_Varispeed =
'vari',
kAudioUnitSubType_DeferredRenderer = 'defr',
kAudioUnitSubType_TimePitch =
'tmpt',
kAudioUnitSubType_Splitter =
'splt',
kAudioUnitSubType_Merger =
'merg',
No, but I can give you a summary:
[~] % auval -s aufc
aufc conv appl - Apple: AUConverter
- wraps an audio converter to do linear PCM conversions (bit depth,
sample rate, interleaving/de-interleaving)
aufc defr appl - Apple: AUDeferredRenderer
- will call for its input on a different thread than it is called on
for its output
aufc merg appl - Apple: AUMerger
- merges two inputs to one output
aufc splt appl - Apple: AUSplitter
- splits one input to two outputs
aufc tmpt appl - Apple: AUTimePitch
- expands or contracts the duration of its input, raises or lowers
the pitch of its input. Both operations are independently applicable
aufc vari appl - Apple: AUVarispeed
- expands or contracts the duration of its input with the pitch
correspondingly being raised or lowered (half as long, twice as
high). Can also do sample rate conversion from its input to its output
HTH
Bill
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tel: +1 408 974 4056
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