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Re: Why a 'prop' error?
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Re: Why a 'prop' error?


  • Subject: Re: Why a 'prop' error?
  • From: Stevo Brock <email@hidden>
  • Date: Wed, 5 Nov 2008 12:17:11 -0800

Hi Eric,

Thanks for your response. The dest description is what I'm getting back from the AudioConverter after setting it up. I'm passing in

mSampleRate: 44100
mFormatID: aac
mFormatFlags: 0
mBytesPerPacket: 0
mFramesPerPacket: 0
mBytesPerFrame: 0
mChannelsPerFrame: 2
mBitsPerChannel: 0
mReserved: 0

This is at the core of our conversion engine which handles many kinds of inputs and outputs and is code that has been working for years. From time to time we enhance it (and try to keep up to date with all the Apple updates). Turns out with the latest combination of everything - OS, QT, our stuff, we are seeing a 'prop' error when setting the converter quality. We are under the impression that, as long as you are setting a valid value from 0 - 127, that this call should not return an error. Obviously we have a wrong impression and I'm trying to understand what situations would generate an error so that we can make the appropriate changes in our code.

-Stevo Brock
 Head of Development
 Monkey Tools, LLC
 www.monkey-tools.com




On Nov 5, 2008, at 11:30 AM, Eric M. Aldrich I wrote:

While I'm not sure why you're getting the 'prop' error, mBytesPerpacket for aac should be 0 -- also make sure you have the mFormatID set to 'aac ' (that last space is really important).

Eric

On 05/11/2008, at 10:14 AM, Stevo Brock wrote:

We're seeing a 'prop' error when setting the converter quality that we haven't seen before. Maybe somebody (Apple?) can explain why we're getting this error.

We create a new AudioConverter with the following:

source
mSampleRate: 48000
mFormatID: lpcm
mFormatFlags: 9
mBytesPerPacket: 8
mFramesPerPacket: 1
mBytesPerFrame: 8
mChannelsPerFrame: 2
mBitsPerChannel: 32
mReserved: 0

dest
mSampleRate: 44100
mFormatID: aac
mFormatFlags: 0
mBytesPerPacket: 1536
mFramesPerPacket: 1024
mBytesPerFrame: 0
mChannelsPerFrame: 2
mBitsPerChannel: 0
mReserved: 0

(note this is the full dest as returned by the AudioConverter).

Then, when calling:
UInt32 u32 = kAudioConverterQuality_Max;
status = AudioConverterSetProperty(converter, kAudioConverterSampleRateConverterQuality, sizeof(UInt32), &u32);


we get a status == 'prop'

This is on OS X 10.5.5, Quicktime 7.5.5, Intel

What are the cases where you can set the kAudioConverterSampleRateConverterQuality property for an AudioConverter and when you can't?

-Stevo Brock
Head of Development
Monkey Tools, LLC
www.monkey-tools.com





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--- Eric M. Aldrich I Apple Core Audio Engineering Audio Codecs




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References: 
 >Why a 'prop' error? (From: Stevo Brock <email@hidden>)

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