Re: AudioDevice Callback Frequency
Re: AudioDevice Callback Frequency
- Subject: Re: AudioDevice Callback Frequency
- From: Jeff Moore <email@hidden>
- Date: Wed, 17 Oct 2007 14:02:13 -0700
Ah, well that's a horse of another color. If you are in control of the
app, then you can have the app set the IO buffer size for your device
using kAudioDevicePropertyBufferFrameSize.
On Oct 17, 2007, at 11:27 AM, Nick Nallick wrote:
I'm using a combination of a user space app and a driver to collect
the machine's audio output. On the client side I've set up an
AudioDevice callback to collect the bit stream, format it, and send
it. How does my client app change the buffer size that I'm getting
in my callback function?
Thanks,
Nick
On Oct 15, 2007, at 7:11 PM, Jeff Moore wrote:
Basically, the answer to your question is no. The driver has no
influence over the IO buffer size a client in user-space might
choose.
On Oct 4, 2007, at 10:13 AM, Nick Nallick wrote:
I'm using a driver very similar to the AudioReflector sample to
capture the machine's audio output, package it and send it to
external hardware for output. Functionally this is similar to
what Airport Express does. My hardware device expects 40 ms
packets of audio sampled at 22.05 kHz (i.e., 882 samples per
packet). My experience is that my AudioDevice callback is being
called with 256 samples at a time (i.e., 11.61 ms at 22.05 kHz).
I'm currently accumulating this data into 40 ms packets and
sending it. Unfortunately this introduces some latency since I
generally have to wait longer than 40 ms for that much data (e.g.,
the first packet is delayed by 6.44 ms but this varies).
Is there any way to tell CoreAudio how often to call my callback,
or some better way to do this?
--
Jeff Moore
Core Audio
Apple
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