Crackling in ZynAddSubFX

[Peter Lutz-2]

I'm very new to Linux audio recording, so I apologize in advance if I'm missing something obvious.

I have a brand new computer with an M-Audio Delta 44 audio card running the latest version of Ubuntu Studio 8.04. I've been experimenting with software synthesizers using a USB MIDI keyboard, and I've managed to get QSynth working very well and have had some success recording that. I thought I'd try ZynAddSubFX since it sounds amazing. The problem I'm having is that the sound crackles (that's the best word I can think of to describe it) when I play it. The very odd thing I've discovered though is that if I record ZynAddSubFX in Ardour, I don't hear any crackling during playback of the recording. It's only as I'm listening to ZynAdd in real-time as I play it. I've tried using different speakers and headphones, but it makes no difference.

I suppose I could just record it and try to ignore the crackling as I play, but it would obviously be ideal to have no crackling at all.

I've tried tweaking both the ZynAdd settings and JACK settings (although my guess is that JACK settings are fine, since I haven't had any issues with recording live instruments or recording QSynth) but to no avail. I have the sample rate in ZynAdd matching the one in JACK (48000Hz) and have tried different buffer sizes in ZynAdd but haven't noticed a difference. I've also noticed that it usually doesn't crackle when I'm using the default instrument in ZynAdd, only once I switch to a different one -- then it seems pretty continuous no matter which instrument I switch to after that.

Does anyone have any ideas as to what could be causing this?

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[norv]

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Are you running a real-time kernel (rt)?
rt kernel is pretty much essential to avoid snap,crackle and pop.

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[Peter Lutz-2]

On Fri, Jun 20, 2008 at 6:40 PM, Norval Watson <norv2001@...> wrote:

Are you running a real-time kernel (rt)?

Yes, I am. It's the default kernel in Ubuntu Studio. I get almost no Xruns in JACK too, so as far as I know, its a separate problem. I have noticed though that one of the few times I'll get one or two Xruns is when I switch instruments within ZynAddSubFX. Not sure if that matters.

In case its helpful, here's some of my JACK settings:

Realtime: checked
Monitor: checked
H/W Monitor: checked
H/W Meter: checked (I'm not sure why I have these last two boxes checked, does it matter?)
Frames/Period: 64 (I've tried 128 too, and that didn't seem to change anything with ZynAdd)
MIDI Driver: seq
Sample Rate: 48000
Periods/Buffer: 2
Port Maximum: 256
Timeout: 500

As for ZynAddSubFX settings, here's some of the relevant ones:

Sample Rate: 48000
Buffer Size: 256
OscilSize: 512
PADsynth Interpolation: Linear (fast)
Append: checked
XML compression level: 3

Any ideas?

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[Peter Lutz-2]

After a little more experimenting, I found a little workaround for this issue... although it's still doesn't exactly shed any light on what's causing the problem. I figure I'll post it here to this mailing list, in case someone with more experience might know what's going on here.

I noticed that every time I switched to a different instrument in the ZynAddSubFX instrument bank, I would get an Xrun in JACK. Then I'd start hearing the crackling sound. The crackling didn't show up at first, only until I switched instruments. I found that if I disconnected ZynAddSubFX from system in the JACK Connection's Audio tab and then reconnected it, the crackling goes away. If I switch to another instrument in ZynAdd, however, I have to repeat this process otherwise the crackling comes back.

Another thing I noticed is that if I turn on "Verbose messages" in JACK, normally I'll steadily get line after line of messages like this:

load = 13.6919 max usecs: 185.000, spare = 1148.000

The load number will increase and the spare will decrease as I play notes. If I switch instruments in ZynAdd however, I get an Xrun and then the load number goes way down in the 1.0 - 2.0 range and as I play notes in ZynAdd, this number is unaffected. Its as if JACK disconnects itself from ZynAdd or something, despite not giving any indication that it has done so.

Oh well. I'm content with this workaround. I just thought I'd post this info in case it may be helpful for someone else.

On Fri, Jun 20, 2008 at 8:03 PM, Peter Lutz <peter@...> wrote:

On Fri, Jun 20, 2008 at 6:40 PM, Norval Watson <norv2001@...> wrote:

Are you running a real-time kernel (rt)?

Yes, I am. It's the default kernel in Ubuntu Studio. I get almost no Xruns in JACK too, so as far as I know, its a separate problem. I have noticed though that one of the few times I'll get one or two Xruns is when I switch instruments within ZynAddSubFX. Not sure if that matters.

In case its helpful, here's some of my JACK settings:

Realtime: checked
Monitor: checked
H/W Monitor: checked
H/W Meter: checked (I'm not sure why I have these last two boxes checked, does it matter?)
Frames/Period: 64 (I've tried 128 too, and that didn't seem to change anything with ZynAdd)
MIDI Driver: seq
Sample Rate: 48000
Periods/Buffer: 2
Port Maximum: 256
Timeout: 500

As for ZynAddSubFX settings, here's some of the relevant ones:

Sample Rate: 48000
Buffer Size: 256
OscilSize: 512
PADsynth Interpolation: Linear (fast)
Append: checked
XML compression level: 3

Any ideas?

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[Atte]

Peter Lutz wrote:
> I
> thought I'd try ZynAddSubFX since it sounds amazing.

It is an amazing synth indeed.

> The problem I'm
> having is that the sound crackles (that's the best word I can think of
> to describe it) when I play it.

ZynAddSubFx has some fundamental problems with realtime. The original
author has given up on this, but Lats Luthman is working on a fix. In
the mean time you'll have to patch it yourself, patches available here:

http://sourceforge.net/tracker/?atid=502314&group_id=62934&func=browse

It might be easier to just get 2.2.1 and apply this patch
(that's the patches I use, wrapped up in one file, since I always forget
which ones to apply):

http://atte.dk/download/attes_patches.diff

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[Dave Phillips]

Atte André Jensen wrote:
> Peter Lutz wrote:
>  
>> I thought I'd try ZynAddSubFX since it sounds amazing.
>>    
>
> It is an amazing synth indeed.
>  
Amen. It is fantastic.

> ZynAddSubFx has some fundamental problems with realtime. The original
> author has given up on this, but Lats Luthman is working on a fix. In
> the mean time you'll have to patch it yourself, patches available here:
>
> http://sourceforge.net/tracker/?atid=502314&group_id=62934&func=browse
>
> It might be easier to just get 2.2.1 and apply this patch
> (that's the patches I use, wrapped up in one file, since I always forget
> which ones to apply):
>
> http://atte.dk/download/attes_patches.diff
>  

Thanks for the diff, Atte. Does anyone know which, if any, distros have
patched ZynAddSubFX with these patches ? I'll rebuild it if I have to,
but it would be nicer if the distro maintainers agreed to use the
patched version.

Best,

dp

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[Patrice-11]

I know I'm a little late... but...

I recompiled zynaddsubfx (cvs patched) and it now works fine with freebob...

Yes!

Peter Lutz wrote:

> I'm very new to Linux audio recording, so I apologize in advance if
> I'm missing something obvious.
>
> I have a brand new computer with an M-Audio Delta 44 audio card
> running the latest version of Ubuntu Studio 8.04. I've been
> experimenting with software synthesizers using a USB MIDI keyboard,
> and I've managed to get QSynth working very well and have had some
> success recording that. I thought I'd try ZynAddSubFX since it sounds
> amazing. The problem I'm having is that the sound crackles (that's the
> best word I can think of to describe it) when I play it. The very odd
> thing I've discovered though is that if I record ZynAddSubFX in
> Ardour, I don't hear any crackling during playback of the recording.
> It's only as I'm listening to ZynAdd in real-time as I play it. I've
> tried using different speakers and headphones, but it makes no difference.
>
> I suppose I could just record it and try to ignore the crackling as I
> play, but it would obviously be ideal to have no crackling at all.
>
> I've tried tweaking both the ZynAdd settings and JACK settings
> (although my guess is that JACK settings are fine, since I haven't had
> any issues with recording live instruments or recording QSynth) but to
> no avail. I have the sample rate in ZynAdd matching the one in JACK
> (48000Hz) and have tried different buffer sizes in ZynAdd but haven't
> noticed a difference. I've also noticed that it usually doesn't
> crackle when I'm using the default instrument in ZynAdd, only once I
> switch to a different one -- then it seems pretty continuous no matter
> which instrument I switch to after that.
>
> Does anyone have any ideas as to what could be causing this?
> ------------------------------------------------------------------------
>
> _______________________________________________
> Linux-audio-user mailing list
> Linux-audio-user@...
> http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
>  

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