Re: Audio distortion after several hours?
Re: Audio distortion after several hours?
- Subject: Re: Audio distortion after several hours?
- From: Daniel Staudigel <email@hidden>
- Date: Mon, 6 Jul 2009 15:34:12 -0700
This point may be either obvious, stupid or both in this context,
since I don't know what kind of EFI shielding your product employs,
but here goes. One thing, that has gotten me several times, is that
you can sometimes hear cellular data transfers which sneak their ways
into improperly shielded cables before they get amplified, and it has
a recognizable "pop-de-pop-de-de-de" sound that comes and goes. If
your clients have a less rigorously setup test environment than you,
this could easily happen.
Cheers,
Daniel
On Jul 6, 2009, at 3:25 PM, Jeff Moore wrote:
Without a better description of the problem, particularly what the
distortion sounds like, how often it happens, precisely when it
started, etc. There really isn't much we can do to help you out.
FWIW, the usual cause of problems like this is that somebody
somewhere has rolled over a 32 bit number. Basically, somebody is
using a 32 bit number where they should be using a 64 bit number.
On Jun 30, 2009, at 2:29 PM, Daniel Mack wrote:
we're developing USB based audio hardware and driver stacks for it
since
a couple of years, and haven't had any serious trouble for a long
time.
However, we've recently got many reports from users of newer
MacBook(Pro)s describing strange effects with audio processing after
some hours of runtime.
The first suspect was the driver, but the effects are too weird to
be explained by a simple software bug, especially because not even
unplugging and reconnecting the device (which involves destroying and
re-creating the AudioEngines from the kernel side) makes any
difference.
Sometimes, not even restarting the whole machine solves it, they say.
And the installations are all brought up to 10.5.7, which
unfortunatly
doesn't help either.
Sadly, I don't have access to any machine showing the effect. But
given that there are quite some sanity checks on the hardware
protocol
level and considering that the driver works pretty well on a varity
of
different Mac hardware models (we've run test for severeal weeks in a
row), I more and more tend to blame some other layer for these
issues,
possibly CoreAudio.
Sorry for not providing more information and more details, but that
vague reports is all I currently got.
Has anyone seen similar things recently?
--
Jeff Moore
Core Audio
Apple
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