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Re: How Do I Use NSCoding with Core Audio Data Types?

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Re: How Do I Use NSCoding with Core Audio Data Types?

Subject: Re: How Do I Use NSCoding with Core Audio Data Types?
From: n ketter <email@hidden>
Date: Fri, 21 Jun 2013 18:32:22 -0700

Thanks, yeah, I'm discovering that.

I've decided to take the route of creating metadata about the audio graph - in types that can be archived - and then rebuilding the AUGraph on the fly.

Thanks again!

On Fri, Jun 21, 2013 at 6:04 PM, Kyle Sluder <email@hidden> wrote:

On Fri, Jun 21, 2013, at 05:04 PM, n ketter wrote:
> I've created a class that contains three properties that are Core Audio
> types:
>
> @interface AudioFilePlayer : NSObject <NSCoding>
>
> @property (assign) AudioUnit mAudioUnit;
> @property (assign) AUNode mNode;
> @property (assign) AudioStreamBasicDescription mStreamFormat;
>
> @end
>
> My app holds an array of objects of type AudioFilePlayer and I want to
> archive and unarchive them using NSCoding. I've written the
> encodeWithCoder: and initWithCoder: methods as follows:

You can't just willy-nilly archive raw bytes to disk and expect decoding
them to make any sense. AudioUnits and AUNodes are pointers into living
objects in an AU graph.

On the other hand, an AudioStreamBasicDescription is just a compendium
of values describing a particular file format, so it is okay to write
those values to disk. However, writing raw C structs to disk is a risky
proposition; you have to worry about padding, alignment, and endianness.

--Kyle Sluder

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References:
	>How Do I Use NSCoding with Core Audio Data Types? (From: n ketter <email@hidden>)
	>Re: How Do I Use NSCoding with Core Audio Data Types? (From: Kyle Sluder <email@hidden>)

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