linuxsampler-devel

[Linuxsampler-devel] Occasional clicks at the beginning of the played sample (fwd)

[Holger M. <ho...@ma...>]

Hi all,

I tested some more. The sfz-file begins with:

<group>
seq_length=2
ampeg_decay=37
ampeg_sustain=0.001
ampeg_release=0.4
loop_mode=loop_continuous
<region>
sample=1_E_a.wav
lokey=0 hikey=28
[...]

I noticed that if I set seq_length=1 the clicks don't happen.

The clicks only happen when
- seq_length=2
- the same note gets play twice, so that it cycles through the 2 samples

Is this a known bug? Is there a workaround by changing some parms in the
sfz-file?



---------- Forwarded message ----------
Date: Thu, 26 Jun 2014 19:09:52 +0200 (CEST)
From: Holger Marzen <ho...@ma...>
To: lin...@li...
Subject: Occasional clicks at the beginning of the played sample

Xubuntu 12.04 LTS,
Kernels 3.5, 3.15-lowlatency and 3.14.3 with realtime patch
16 GB RAM, Core i5, SSD (desktop and notebook computer)
linuxsampler svn 2482 (I also tried a recent one yesterday but it crashed)
sfz engine used
jack used

Tested with linuxsampler standalone, linuxsampler-dssi and
linuxsampler-lv2

I experience occasional clicks at the beginning of played notes, about
one every 10-20 seconds, varying in their strength. It doesn't depend of
the soundcard used. It happens even with the dummy sound device when
playing a MIDI track with Rosegarden or Qtractor.

I managed to catch twice the same note/sample, one deformed with click,
one clean:
http://www.marzen.de/tmp/click.jpg

This is another one with click. It can be seen in the waveform:
http://www.marzen.de/tmp/click2.jpg

It seems that some samples simply get lost.

It happens on both of my computers.

There are no problems with JACK processing other audio, at least no that
I ever noticed.

I run out of ideas. This is a big problem for me because with occasional
klicks when using linuxsampler I can't use my sfz-soundfonts for high
quality recording.

Any ideas?

Re: [Linuxsampler-devel] Occasional clicks at the beginning of the played sample (fwd)

[Christian S. <sch...@li...>]

On Thursday 26 June 2014 19:49:21 Holger Marzen wrote:
> I tested some more. The sfz-file begins with:
> 
> <group>
> seq_length=2
> ampeg_decay=37
> ampeg_sustain=0.001
> ampeg_release=0.4
> loop_mode=loop_continuous
> <region>
> sample=1_E_a.wav
> lokey=0 hikey=28
> [...]
> 
> I noticed that if I set seq_length=1 the clicks don't happen.
> 
> The clicks only happen when
> - seq_length=2
> - the same note gets play twice, so that it cycles through the 2 samples
> 
> Is this a known bug? Is there a workaround by changing some parms in the
> sfz-file?

I am not an SFZ expert, so maybe Andreas or Grigor can comment better on it.

seq_* opcodes seems to define "round robin" selection for regions in the SFZ 
format. I just had a short look at current SFZ code, and as far as I could see 
it right now, round robin selection in the SFZ engine could indeed be buggy.

bool Region::OnKey(const Query& q) [src/engines/sfz/sfz.cpp]

is called by the SFZ engine on each region, when a new note was triggered, to 
check which region shall be used and played. However that method ATM assumes 
to be called only once and due to this increments the round robin counter at 
the end of its call. The SFZ engine however calls this in a while loop:

	while (::sfz::Region* region = q.next()) {
							[src/engines/sfz/Engine.cpp, line 110]

which seems to cause the misbehavior you encountered. That is, that it falsely 
also triggers the 2nd region you have there at the same time.

So IMO the round robin counter should be incremented after that loop, but not 
inside Region::OnKey().

CU
Christian

Re: [Linuxsampler-devel] Occasional clicks at the beginning of the played sample (fwd)

[Holger M. <ho...@ma...>]

On Fri, 27 Jun 2014, Christian Schoenebeck wrote:

> seq_* opcodes seems to define "round robin" selection for regions in the SFZ 
> format. I just had a short look at current SFZ code, and as far as I could see 
> it right now, round robin selection in the SFZ engine could indeed be buggy.
> 
> bool Region::OnKey(const Query& q) [src/engines/sfz/sfz.cpp]
> 
> is called by the SFZ engine on each region, when a new note was triggered, to 
> check which region shall be used and played. However that method ATM assumes 
> to be called only once and due to this increments the round robin counter at 
> the end of its call. The SFZ engine however calls this in a while loop:
> 
> 	while (::sfz::Region* region = q.next()) {
> 							[src/engines/sfz/Engine.cpp, line 110]
> 
> which seems to cause the misbehavior you encountered. That is, that it falsely 
> also triggers the 2nd region you have there at the same time.

I made a soundfont with 2 different (in frequency) samples, so I could
hear if both samples are played together instead alternating. It didn't
happen. They were never played together. So this bug candidate doesn't
seem to be one.

I investigated the sound font some more. The clicking sample was
different compared to the others: it lacked loop information in the
wav-header. Since there wasn't any loop_start/loop_end in the sfz-file
linuxsampler probably used the defaults 0/0. Could be a reason for the
occasional klicks.

Another "bug" in the soundfont could be the release sound:
  ampeg_decay=37
  loop_mode=one_shot
  trigger=release
One_shot mode together with a very long decay could possibly lead to
voice-stealing, another possible source of occasional klicks.


TL;DR
-----
After fixing the soundfont I have now much better results.