On Wed, 07 Dec 2016 15:52:15 -0500
termtech <termtech@xxxxxxxxxx> wrote:
> On Wednesday, December 7, 2016 10:43:22 AM EST David Jones wrote:
> > On Dec 7, 2016 06:48, termtech <termtech@xxxxxxxxxx> wrote:
> > > On Wednesday, December 7, 2016 7:34:25 AM EST David Klann wrote:
> > > > On 12/03/2016 01:50 PM, termtech wrote:
> > > > > On Saturday, December 3, 2016 1:20:09 PM EST David Klann wrote:
> > > > >> Greetings,
> > > > >>
> > > > >> Long-time Linux user, and relatively new JACK user here. I have built
> > > > >> ...
> > > > >
> > > > > Hello, this might be a long shot, but maybe not.
> > > > > You mentioned it did this when Jack was disabled,
> > > > >
> > > > > so it seems Jack is not the problem.
> > > > >
> > > > > Look for the LAU thread on Wednesday titled:
> > > > > " [SOLVED] Crackles in audio, drifting intermittent noise etc."
> > > > > I was having very strange phasing problems, although I didn't notice
> > > > >
> > > > > from channel to channel but I wasn't really listening for that.
> > > > >
> > > > > I knew it was hardware related, only that could cause it.
> > > > >
> > > > > My ONLY solution was changing the number of enabled CPU cores,
> > > > >
> > > > > either through my BIOS or through Linux commands such as:
> > > > > echo 0| sudo tee /sys/devices/system/cpu/cpu3/online
> > > > > cat /sys/devices/system/cpu/cpu3/online
> > > > >
> > > > > I found that I must run with just ONE core for the most stability.
> > > > > (I had posted that I found TWO cores were OK but actually
> > > > >
> > > > > further test revealed it was not OK.)
> > > > >
> > > > > So try:
> > > > > echo 0| sudo tee /sys/devices/system/cpu/cpu1/online
> > > > > echo 0| sudo tee /sys/devices/system/cpu/cpu2/online
> > > > > echo 0| sudo tee /sys/devices/system/cpu/cpu3/online
> > > > >
> > > > > cpu0 will always be online.
> > > > >
> > > > > Tim.
> > > >
> > > > Hi Tim!
> > > >
> > > > Thanks for this tip! I probably never would have considered this even
> > > > though it was a vague, nagging thought in the back of my head.
> > > >
> > > > Disabling three of the four cores (or hyperthreads?) on the CPU fixed
> > > > the problem for us!
> > > >
> > > > Specifically (and to tweak your command set), I placed the following in
> > > > /etc/rc.local to ensure the CPU disabling survives a reboot:
> > > >
> > > > <code>
> > > > for c in 1 2 3; do echo 0 > /sys/devices/system/cpu/cpu${c}/online; done
> > > > </code>
> > > >
> > > > In reading the "Crackles in audio..." thread, I am curious to know why
> > > > this happens with some CPUs and not with others. My understanding is
> > > > that this is fundamentally a timing issue between processes that are
> > > > running on different CPUs (or cores). So, while it's not specifically a
> > > > JACK issue, if the jackd process is running on CPU0 and the audacity
> > > > process is running on CPU3 then a timing error may be introduced between
> > > > those two CPU's. Is that a reasonable summary of the effect?
> > > >
> > > > And for my next trick, I will experiment with the taskset(1) command to
> > > > set processor affinity for the audio processes. Maybe we can leave all
> > > > four CPU's enabled and still avoid the "left-right channel skew"
> > > > problem.
> > >
> > > Ah thanks, I was looking for something like taskset.
> > > I wondered if the entire audio chain, from driver to application,
> > > should somehow be set to one CPU even if all four are enabled.
> > > Please let us know how it works out for you.
> > >
> > > I am very late to this multi-core party. It's my first such PC.
> > > I am sure this episode has been repeated before in other threads.
> > > It's hard to dig through the confusion and misinformation.
> > > Even though I did research these CPUs before buying, I didn't
> > > expect it would affect things in this manner.
> > >
> > > Tim.
> > >
> > > > Thank you everyone who weighed in on this, and especially Paul for
> > > > pointing out that it cannot be an issue introduced by JACK.
> > > >
> > > > Best regards,
> > > >
> > > > ~David Klann
> >
> > Well, I have 2 PCs I do audio on. One has 4-core AMD Phenom II (no
> > hyperthreading). Other has Intel i7 (4 cores + hyperthreading). Have never
> > tweaked anything like what you're talking about and have never had any such
> > problem as you had.
> >
> > I do not have Pulseaudio installed on either of them.
> >
> > My final guess at root of problem: hardware issue with CPU itself. Maybe
> > some manufacturing defect that only manifests when all cores are in use?
>
> It appears to be something related to certain (older?) PCI audio cards.
> Although, I think Len said he's running a similar card as mine
> and hasn't seen any problems.
>
> An older SBLive! PCI card appeared to work fine. Maybe I should test again...
>
> Tim.
This is most odd. I'm fortunate to have access to several quite different
multicore machines. (2 and 4 core), one working with an elderly 2496, the
others using a KA6 - all the onboard sound chips are rubbish - none of them show
this problem.
Probably not a lot of help though :/
--
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.
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