Re: kAudioDevicePropertyStreamFormat in input
Re: kAudioDevicePropertyStreamFormat in input
- Subject: Re: kAudioDevicePropertyStreamFormat in input
- From: Jeff Moore <email@hidden>
- Date: Wed, 26 Jun 2002 11:46:30 -0700
On Wednesday, June 26, 2002, at 12:05 AM, Jan Trutzschler wrote:
the function
AudioDeviceGetProperty(device, 0, true,
kAudioDevicePropertyStreamFormat, &count, &inputStreamDesc);
returns a kAudioDevicePropertyStreamFormat on several audio devices
(usb audio/ quicksilver box).
if i ignore this error it seems that everything is running normally.
that means i can actually access the input.
is there any explination for this?
I assume you mean that AudioDeviceGetProperty() is returning an error
of some kind when trying to get the format of the first input stream.
kAudioDevicePropertyStreamFormat is a property constant.
Which error is it specifically is it and on what piece of hardware?
It's hard to say why this would be without knowing the actual error,
but here are some generalities:
kAudioHardwareIllegalOperationError: usually means the device ID isn't
valid, but may have other meanings
kAudioHardwareUnspecifiedError: means either the HAL implementation
threw an unrecognized exception or more commonly some kind of
CoreFoundation routine failure.
kAudioHardwareBadPropertySizeError: means what it says.
kAudioDeviceUnsupportedFormatError: means that the device doesn't have
a stream that corresponds to the section (input or output) or the
device channel number (0 is special and always refers to the first
stream in the case of formats).
There may be other errors, but these were the only ones I could find in
the code. Whatever the error code, it also means that the HAL did not
touch the contents of the memory passed in to hold the output result.
This means it will have the same value on output as it did on input. If
you had previously initialized the structure, it could appear as if the
HAL is returning valid information, when it really isn't.
--
Jeff Moore
Core Audio
Apple
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