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Re: Format Converters
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Re: Format Converters


  • Subject: Re: Format Converters
  • From: Doug Wyatt <email@hidden>
  • Date: Thu, 13 Oct 2005 14:03:56 -0700

I would just add:

- AUConverter essentially wraps an AudioConverter. Set element 0's input and output stream descriptions to any PCM format.
- AUDeferredRenderer passes canonical Float32 samples from input to output, but calls for input on a secondary thread internal to the AU. It is described in more detail in AudioUnitProperties.h.


Doug

On Oct 13, 2005, at 12:18, William Stewart wrote:

The rule we've applied to this in AU Lab (which will host AU Converter units if the source of a strip is a Generator AU) is that the AU publishes a "custom" view.

We use this as a way for the AU to tell us that it has applicability as a "user" type of AU, compared with the more generic convert data role (or some other data management) that converter units do.

So, in the list below, the only converter AUs that AU Lab will show is the time pitch and varispeed.

The following AUs I don't think have any use as some kind of arbitrarily selectable "processing-type" AU to a user:

AULab also handles the split and merge AUs as a way of dealing with sidechains:
- AU Splitter is used so that the user can arbitrarily create a side chain output from anywhere within a strip, and then make that a "source" for a new strip
- AU Merger is used so that the user can arbitrarily grab some channels from the input side of the audio device and mix these with the existing strips output to a single output.


AU Converter is an AU that will perform float-int-float, interleave/ deinterleave, sample rate conversions. It forms the basis of the data conversion services that are vended by the generic and device output units. Its provided as a separate AU to allow for arbitrary conversions to be used within a signal path.

AU Deferred Renderer is there to provide a threaded context for an AU Render chain. It introduces buffering internally, it gets its input on one thread, buffers it, and provides to the AU's Render method (which is being called on whatever thread it is called on by the user). This would need I think some extensive custom support in a host app.

HTH

Bill


On 13/10/2005, at 8:10 AM, Jeremy Sagan wrote:

I have recently added support for format converters to my application. I am just wondering where there is documentation on what exactly these audio units do, their correct usage and what their parameters mean. In OS X 10.4 I notice the following audio units:

AUConverter
AUDeferredRenderer
AUMerger
AUSplitter
AUTimePitch
AUVarispeed

I have a pretty good idea what the last 2 do. I have found very limited info in the file AudioUnitParameters.h but that is it.

Jeremy

-- Doug Wyatt Core Audio, Apple

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References: 
 >Format Converters (From: Jeremy Sagan <email@hidden>)
 >Re: Format Converters (From: William Stewart <email@hidden>)

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