Re: IOAudioStream[0x148cc00]::clipIfNecessary() - Error:
Re: IOAudioStream[0x148cc00]::clipIfNecessary() - Error:
- Subject: Re: IOAudioStream[0x148cc00]::clipIfNecessary() - Error:
- From: William Stewart <email@hidden>
- Date: Tue, 02 Nov 2004 12:50:30 -0800
The main thing we'd want to see from this is a bug report that would
associate some known audio glitching where its not expected... We're
certainly interested in following through with these problems, figuring out
if this is some unexpected latency in the system, etc...; it helps us
immensely if we can reproduce known cases.
As to what can cause this - it depends... Contested locks are usually a good
candidate - and both Shark and latency tracing are some of the tools we use
to investigate these problems...
If you're an app writer and have a reasonably reproducible scenario - one
approach I'd recommend is the following.
Use the latency tracing code in the SDK (CALatencyLog in Public Utility)...
Estalish logic in your code where you can feed in a percent CPU usage
*above* which you expect that something bad is going on - then that triggers
a latency trace...
For instance, lets say that you are doing some simple I/O that should only
consume 10% CPU time in the I/O proc. But, every now and then you get a
spike of CPU usage to about 20 or 30% (or even worse), but your code is not
doing (or lets say it shouldn't be!) anything different that would cause
this... So, then you set it up, so if the I/O usage is above 20% you take a
latency trace for the previous time (I'd recommend being able to trace about
10 msecs before the I/O proc would have started executing)... This gives you
a very narrow and focussed trace log of activity in the system covering the
time that the problem arose - its certainly a lot easier than going through
megabytes of trace logs!
We're happy to go through these traces with you to help understand them.
Bill
On 2/11/04 3:21 AM, "Stefan Haller" <email@hidden> wrote:
> We are receiving customer reports about audio dropouts. They tell us
> that they find console log entries like these:
>
> Oct 28 23:38:05 localhost kernel:
> IOAudioStream[0x148cc00]::clipIfNecessary() - Error: attempting to clip to a
> position more than one buffer ahead of last clip position
> (416c9,219)->(416ce,69).
> Oct 28 23:38:05 localhost kernel:
> IOAudioStream[0x148cc00]::clipIfNecessary() - adjusting clipped position to
> (416cd,219)
>
> This seems to happen with various hardware, for example Motu 828, or
> M-Audio Audiophile FW.
>
> Is this a problem of the driver, of the hardware, or of the host
> application? What can we do to figure out what's wrong?
>
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