Re: AudioStreams
Re: AudioStreams
- Subject: Re: AudioStreams
- From: Greg Hamilton <email@hidden>
- Date: Tue, 19 Nov 2002 14:02:07 +1100
Ok, I think I understand.
I can use the MTCoreAudio framework to get an NSArray of available
streams for a device and direction (record / playback). For the record
direction of my device (a Griffin iMic) it returns one stream which is
an interleaved two channel (stereo) stream of Float 32 data sampled at
44.1KHz. Should I be able to change the properties of this stream, such
as the sample rate ? And if I do change the properties should I see a
change in the format of the data delivered to my AudioDevice ioProc ?
Greg
On Tuesday, November 19, 2002, at 05:03 AM, Jeff Moore wrote:
In the HAL, an AudioStream is an object that encapsulates one
interleaved, unidirectional stream of data on a particular
AudioDevice. In the HAL's API, there are routines for getting and
setting properties for streams. The most important role an AudioStream
plays is the arbiter of the format in which your IOProc provides it's
data. AudioStreamXXXX routines are the preferred way to get/set the
formats of the device as opposed to the similar AudioDeviceXXXX
routines.
On Sunday, November 17, 2002, at 04:06 PM, Greg Hamilton wrote:
Hi,
I've written an app to record / playback using CoreAudio and
MTCoreAudio. It's pretty simple, just an MTCoreAudioDevice object for
record and another for playback, each with it's own ioProc for
reading / writing data.
I've read both the quite old coreaudio.pdf from Apple
(http://developer.apple.com/audio/pdf/coreaudio.pdf) and the
MTCoreAudio docs. Both make mention of AudioStreams and the
MTCoreAudio framework even provides two Objective C classes as
wrappers for AudioStreams and AudioStreamDescriptions but neither
documents explain exactly what AudioStreams are for nor how to use
them so I'm left making guesses based on the methods available in the
MTCoreAudioStream class.
What are AudioStreams and why would I use them ?
Greg
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--
Jeff Moore
Core Audio
Apple
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