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QT7 changes behavior of AudioConverterConvertBuffer
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QT7 changes behavior of AudioConverterConvertBuffer


  • Subject: QT7 changes behavior of AudioConverterConvertBuffer
  • From: "Tim Dorcey" <email@hidden>
  • Date: Sun, 01 May 2005 20:42:18 -0700
  • Importance: Normal

In case anyone else is having problems with audio corruption after QT7/Tiger
installation, you might have a look at places you are using AudioConverter.
I had been trying to use AudioConverterConvertBuffer for sample rate
conversions, which seemed to work fine before QT7/Tiger.

On one system that I got some debugging going on, ConvertBuffer was
returning an error code of 1768846202 on alternating calls, causing me to
ignore that chunk of audio.  If I just ignore the error code instead, it
apparently sounds okay, though I haven't confirmed it is exactly right.
Also, I was surprised to see it always returning the same amount of data for
a given amount of input data, when I would expect it to be periodically
outputting accumulation of "fractional" samples (as it does on my pre-QT7
system).

It may also be that ConvertBuffer has not changed, but
AudioConverterGetProperty is behaving differently for
kAudioConverterPropertyCalculateOutputBufferSize.  I was using that to
determine how much data to ask ConvertBuffer to produce.  Perhaps
GetProperty is ignoring internally accumulated state, and then maybe
1768846202 means I didn't allow enough output for all the input.

Not sure if this is a bug, since I can't seem to find any explanation of how
things are supposed to work.  Perhaps I just got lucky prior to QT7.  Does
anyone know where is the hidden trove of CoreAudio docs?

Tim

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