Re: AudioConverter's algorithm vs complexity vs quality
Re: AudioConverter's algorithm vs complexity vs quality
- Subject: Re: AudioConverter's algorithm vs complexity vs quality
- From: William Stewart <email@hidden>
- Date: Mon, 28 Jul 2008 18:40:16 -0700
On Jul 28, 2008, at 4:29 AM, Mike Kluev wrote:
AudioToolbox.framework/AudioConverter.h states this:
### @constant kAudioConverterSampleRateConverterAlgorithm
### DEPRECATED: please use
kAudioConverterSampleRateConverterComplexity instead
while the doc at
http://developer.apple.com/documentation/MusicAudio/Reference/CoreAudio/audio_toolbox/chapter_4_section_4.html
states this instead:
### kAudioConverterSampleRateConverterAlgorithm = 'srci'
### Deprecated. Use kAudioConverterSampleRateConverterQuality instead.
Which one is corect?
Both.
The first is deprecated to "Complexity", the second is deprecated to
"Quality".
So, the basic layout is that there is three complexity settings (in
Leopard):
line - Linear
norm - Normal
bats - "mucho" complexity :)
Quality is a 0 to 127 setting, and for norm and bats will determine
the quality of the output (higher quality is higher CPU cost and
longer execution time).
For most situations (particularly real time) "norm" and Medium is ok.
If you want better playback, then setting quality to max is a good
idea - but you should look at the difference in CPU utilisation to see
if this affects you in any way.
If you are mastering content, then we would recommend using bats
complexity (and probably max quality unless the time taken really
matters)
Bill
I noticed that kAudioConverterSampleRateConverterComplexity doesn't
matter at all, only kAudioConverterSampleRateConverterQuality matters.
Is this correct observation and correct behavior? If yes, what is
the purpose
of kAudioConverterSampleRateConverterComplexity?
Could I pass values other than kAudioConverterQuality_Max ... Min
to the quality parameter?
My sound is mono 16 bit integer uncompressed PCM if that matters.
Mike
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