best way to get rate conversion
best way to get rate conversion
- Subject: best way to get rate conversion
- From: "Phil Burk" <email@hidden>
- Date: Thu, 10 Oct 2002 10:01:18 -0700
I am preparing to add support for sample rate conversion to PortAudio, an
open-source cross-platform audio API used in many projects.
http://www.portaudio.com/
I currently use the HAL (Hardware Abstraction Layer ), making calls to
AudioDeviceAddIOProc() and AudioDeviceStart(). This technique is close to
the hardware and provides excellent latency but does not provide sample rate
conversion. My PowerBook G3, for example, only supports 44100 Hz.
A higher level API involving the AudioOutputUnit does provide sample rate
conversion by setting "austream.mSampleRate".
Questions:
1) Is the AudioOutputUnit the best way to implement basic audio I/O if I
want sample rate conversion?
2) I know that SRC can increase latency because it involves filters. But for
rates that match the HW rate (eg. 44100 Hz) will using the AudioOutputUnit
increase the latency significantly versus using the HAL?
Thanks,
Phil Burk
http://www.softsynth.com/ - JSyn, software development
http://www.javasonics.com/ - audio I/O for Java and the web
http://www.transjam.com/ - collaboration server, WebDrum
http://www.portaudio.com/ - portable audio API for 'C'
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