Re: Coreaudio performance under load
Re: Coreaudio performance under load
- Subject: Re: Coreaudio performance under load
- From: Jeff Moore <email@hidden>
- Date: Wed, 15 Feb 2006 14:15:53 -0800
You need to figure out why you are getting drop-outs before we can
offer some help in fixing them. The reasons could be many ranging
from something simple like your code just doing too much work in the
IOProc to something complicated like your code blocking on a lock or
allocating memory or something like that.
Toward this end, you'll need to instrument your own code so that you
can figure out what's going on. You should also familiarize yourself
with the various tools we have on the system to help you diagnose
issues like this. Shark, for example, provides an excellent way to
look at what's going on in your program from the system's point of
view. You'll find the system trace facility in Shark exceptionally
helpful.
Another tool that you'll want to use is the IO Cycle Telemetry window
in HALLab, which is part of the Core Audio SDK and can be found in /
Developer/Examples/CoreAudio/HAL/HALLab). This window allows you to
tap into the running HAL in another process and spy on what's going
on. It provides a way to pin-point the general reasons why an
overload happens. The telemetry can also be used to trigger kernel
traces that help figure out a little more precisely why the IO thread
isn't getting the time it needs.
You should leaf through this list's archives as the topic of
diagnosing drop-outs has come up many times, as you might imagine.
Also, we are more than happy to help you puzzle through the HALLab or
kernel trace output to help figure out what's going wrong.
On Feb 11, 2006, at 2:03 PM, Michael Guntsche wrote:
I recently finished an auhal output plugin for the libao library
(http://www.xiph.org/ao).
During my testing I noticed that I only need some higher load on my
powerbook (bouncing dock icon + compile) to get buffer underuns
(stuttering). First I thought that I did something wrong and so I
tried SDL which also has support for CoreAudio, but I got buffer
underruns there too quite easy.
I know that I could increase the ringbuffer size but this also
increases latency. Since I never get dropouts in quicktime or
iTunes I wonder how they do that.
--
Jeff Moore
Core Audio
Apple
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