13 Mar
2007
13 Mar
'07
10:58 a.m.
Greetings:
I have a problem with a piece I'm working on in Rosegarden 1.5. I've
appended the text I sent to Chris Cannam, along with his response (I
hope he doesn't mind). Btw, the machine is based on an AMD64 3200+, with
2G RAM and an 80G hard drive. Sound runs through an M-Audio Delta 66.
Distro is 64Studio 2.0.
My questions lead, Chris's replies follow :
That sounds a bit like a plugin denormal problem. Although denormals
are usually less of a problem on AMD64.
The 0(1024) in qjackctl I think means that JACK has reported 1024 xruns
via the reporting API but they haven't been mentioned in the message
log. I don't actually know what causes that. Does CPU usage (as
reported by a plain old CPU usage reporting program) actually peak at
that point?
Probably not, or at least I wouldn't expect it to suddenly peak if usage
has previously been on the low side.
The only thing RG does that may affect CPU usage drastically during
playback is that it doesn't start running plugins until they actually
have something to work on, and it stops running them if they've fallen
silent for a certain period and have no more input coming up (this is
in contrast to e.g. Ardour which runs plugins all the time during
playback, taking a more strictly correct view).
So, if anyone has anything to add to Chris's assessment, I'd like to
know about it. If the problem is indeed related to denormals, is there a
way to fix it ? Comments and suggestions are most welcome.
Best,
dp
2) I've
written a piece consisting of six tracks with these specs:
Tr.1 (audio) drum loop, repeated, 1 plugin (CAPS plate reverb 2x2)
Tr.2 (MIDI) bass part, repeated, uses patch from 8mbgmsfx.sf2
soundfont, no fx (part is rendered via QSynth which does have its
reverb active)
Tr.3 (audio) rhythm guitar loop, repeated, 3 fx (dj EQ mono, CAPS
compress, CAPS plate 2x2)
Tr.4 (audio) lead guitar, no repeats or copy, 4 fx (CAPS plate 2x2,
AmpIV, AM pitch shifter, multiband EQ)
Tr.5 (audio) riff loop, copied, 3 fx (dj EQ mono, CAPS compress,
CAPS plate 2x2)
Tr.6 (audio) another percussion loop, copied, no fx
At 120 BPM the piece is 200+ measures long. It plays along
swimmingly, but at m. 74 (about two minutes into the piece) the sound
cuts out entirely. RG continues to run, but it pops up a message
telling me that there's not enough CPU for realtime processing. Up to
that point JACK reports approximately 33% CPU usage and no errors,
but then it reports 0(1024) for xruns. I don't know what the second
number (1024) means to JACK, but it keeps rising (with no sound)
until I halt RG.
So my question
is: Given my machine, should my CPU be topping out in
this scenario ?
13 Mar
13 Mar
11:10 a.m.
Hi Dave,
To be getting problems from denormals you really need a stretch of
silence going into some effects processing. From your description it
doesn't seem like that's very likely. If you do have a stretch of
silence, add a small amount of noise to the track, and if it goes
away you have a denormal bug, and you can shoot the plugin developer :)
It could also be a NaN problem, which have similar symptoms but can
happen at any time. Their uncommon, but much nastier to find and fix.
If you skip forward to near the point where it jams and play from
there, does it still jam? Have you tried muting some tracks to see if
it still happens?
- Steve
On 13 Mar 2007, at 15:08, Dave Phillips wrote:
Greetings:
I have a problem with a piece I'm working on in Rosegarden 1.5.
I've appended the text I sent to Chris Cannam, along with his
response (I hope he doesn't mind). Btw, the machine is based on an
AMD64 3200+, with 2G RAM and an 80G hard drive. Sound runs through
an M-Audio Delta 66. Distro is 64Studio 2.0.
My questions lead, Chris's replies follow :
That sounds a bit like a plugin denormal problem. Although
denormals are usually less of a problem on AMD64.
The 0(1024) in qjackctl I think means that JACK has reported 1024
xruns via the reporting API but they haven't been mentioned in the
message log. I don't actually know what causes that. Does CPU
usage (as reported by a plain old CPU usage reporting program)
actually peak at that point?
Probably not, or at least I wouldn't expect it to suddenly peak if
usage has previously been on the low side.
The only thing RG does that may affect CPU usage drastically during
playback is that it doesn't start running plugins until they
actually have something to work on, and it stops running them if
they've fallen silent for a certain period and have no more input
coming up (this is in contrast to e.g. Ardour which runs plugins
all the time during playback, taking a more strictly correct view).
So, if anyone has anything to add to Chris's assessment, I'd like
to know about it. If the problem is indeed related to denormals, is
there a way to fix it ? Comments and suggestions are most welcome.
Best,
dp
2)
I've written a piece consisting of six tracks with these specs:
Tr.1 (audio) drum loop, repeated, 1 plugin (CAPS plate reverb 2x2)
Tr.2 (MIDI) bass part, repeated, uses patch from 8mbgmsfx.sf2
soundfont, no fx (part is rendered via QSynth which does have its
reverb active)
Tr.3 (audio) rhythm guitar loop, repeated, 3 fx (dj EQ mono, CAPS
compress, CAPS plate 2x2)
Tr.4 (audio) lead guitar, no repeats or copy, 4 fx (CAPS plate
2x2,
AmpIV, AM pitch shifter, multiband EQ)
Tr.5 (audio) riff loop, copied, 3 fx (dj EQ mono, CAPS compress,
CAPS plate 2x2)
Tr.6 (audio) another percussion loop, copied, no fx
At 120 BPM the piece is 200+ measures long. It plays along
swimmingly, but at m. 74 (about two minutes into the piece) the
sound
cuts out entirely. RG continues to run, but it pops up a message
telling me that there's not enough CPU for realtime processing.
Up to
that point JACK reports approximately 33% CPU usage and no errors,
but then it reports 0(1024) for xruns. I don't know what the second
number (1024) means to JACK, but it keeps rising (with no sound)
until I halt RG.
So my
question is: Given my machine, should my CPU be topping out in
this scenario ?
11:36 a.m.
New subject: [linux-audio-dev] Re: [linux-audio-user] denormals or ... ?
On Tue, 2007-03-13 at 10:08 -0500, Dave Phillips wrote:
So, if anyone has anything to add to Chris's
assessment, I'd like to
know about it. If the problem is indeed related to denormals, is there
a
way to fix it ? Comments and suggestions are most welcome.
i made a few experiences regarding to denormals in Aldrin/libzzub.
numerous plugins had their own fixes for denormalization (and i know
that CAPS has a fix too, which is to add a -250dB square wave to avoid
the value to go off the scale). AMD cpus do not have that problem most
of the time, so the problem relates mostly to Intel cpus.
If all plugins and the host use SSE fp arithmetic, the host can turn off
denormalization through SSE intrinsics for each render step.
We did exactly that. I enabled the builds for SSE, removed any
denormal-fix related code and just disabled denormals. it makes the code
a lot cleaner and faster, however the downside is that non-SSE cpus will
not benefit from that advantage.
--
Leonard Ritter
-- Freelance Art & Logic
-- http://www.leonard-ritter.com
11:54 a.m.
New subject: [linux-audio-dev] Re: [linux-audio-user] denormals or ... ?
[Leonard Ritter]
On Tue, 2007-03-13 at 10:08 -0500, Dave Phillips wrote:
Unfortunately, there seems to be a denormal problem with at least
AmpIV in CAPS. The fix you mention works reasonably well for most
plugins, but in the Amp series there's a simple dc-blocking IIR
running at 8x fs that as far as I remember isn't 'renormalized' -- I
keep meaning to verify the problem and this likely culprit, but I
never seem to get around to it.
Dave, I think your problems may well be caused by denormals; in fact I
think it's the most probable cause. Does the problem persist if you
remove AmpIV from the processing setup? The other CAPS plugins
_should_ be safe (can't guarantee 100% though).
Cheers, Tim
So, if anyone has anything to add to Chris's
assessment, I'd like to
know about it. If the problem is indeed related to denormals, is there
a
way to fix it ? Comments and suggestions are most welcome.
i made a few experiences regarding to denormals in Aldrin/libzzub.
numerous plugins had their own fixes for denormalization (and i know
that CAPS has a fix too, which is to add a -250dB square wave to avoid
the value to go off the scale). AMD cpus do not have that problem most
of the time, so the problem relates mostly to Intel cpus.
1:19 p.m.
New subject: [linux-audio-dev] Re: [linux-audio-user] denormals or ... ?
Tim Goetze wrote:
Unfortunately, there seems to be a denormal problem
with at least
AmpIV in CAPS. The fix you mention works reasonably well for most
plugins, but in the Amp series there's a simple dc-blocking IIR
running at 8x fs that as far as I remember isn't 'renormalized' -- I
keep meaning to verify the problem and this likely culprit, but I
never seem to get around to it.
Dave, I think your problems may well be caused by denormals; in fact I
think it's the most probable cause. Does the problem persist if you
remove AmpIV from the processing setup? The other CAPS plugins
_should_ be safe (can't guarantee 100% though).
Thanks for the tip, Tim, that fixed it. The AmpIV plugin was the
culprit, I replaced with the Simple Amplifier and the truncated play
problem is solved. Sad to say too, because I really like AmpIV.
So now we know. Thanks to all who replied, you guys are the cat's meow. :)
Best,
dp
19 Mar
19 Mar
10:34 a.m.
New subject: [linux-audio-dev] Re: [linux-audio-user] denormals or ... ?
Dave Phillips <dlphillips(a)woh.rr.com> writes:
that fixed it
I've added a note about this to:
http://apps.linuxaudio.org/apps/all/caps
--
Esben Stien is b0ef@e s a
http://www. s t n m
irc://irc. b - i . e/%23contact
sip:b0ef@ e e
jid:b0ef@ n n
1:03 p.m.
New subject: [linux-audio-dev] Re: [linux-audio-user] denormals or ... ?
[Esben Stien]
Dave Phillips <dlphillips(a)woh.rr.com> writes:
I have a patch ready that should take care of this problem. Anyone
willing to give it a try in real life? (Dave got it per mail but
it seems he's too busy ...)
Cheers, Tim
that fixed it
I've added a note about this to:
http://apps.linuxaudio.org/apps/all/caps
1:22 p.m.
New subject: [linux-audio-dev] Re: [linux-audio-user] denormals or ... ?
Tim Goetze wrote:
I have a patch ready that should take care of this
problem. Anyone
willing to give it a try in real life? (Dave got it per mail but
it seems he's too busy ...)
Ach, I didn't send a report ? My bad, especially because the patch
didn't fix the problem. For the moment I'm using another amplifier
plugin that works, but I'd prefer ampIV.
Best,
dp
1:33 p.m.
New subject: [linux-audio-dev] Re: [linux-audio-user] denormals or ... ?
[Dave Phillips]
Tim Goetze wrote:
Thanks, I'll send my DSP engineers back to their drawing boards then.
They sure are a worthless bunch, I think I'll lay off every tenth to
improve morale.
Cheers, Tim
I have a patch ready that should take care of
this problem. Anyone willing to
give it a try in real life? (Dave got it per mail but it seems he's too busy
...)
Ach, I didn't send a report ? My bad, especially because the patch didn't
fix
the problem. For the moment I'm using another amplifier plugin that works, but
I'd prefer ampIV.
1:42 p.m.
New subject: [linux-audio-dev] Re: [linux-audio-user] denormals or ... ?
Tim Goetze wrote:
Thanks, I'll send my DSP engineers back to their
drawing boards then.
They sure are a worthless bunch, I think I'll lay off every tenth to
improve morale.
Glad to be of service, Tim. As you're the head honcho in the outfit, be
sure to give yourself a hefty raise after the layoffs.
Best,
dp
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9 comments
5 participants
participants (5)
-
Dave Phillips -
Esben Stien -
Leonard Ritter -
Steve Harris -
Tim Goetze