LMMS
Playing a sample or instrument with LS Filter's cutoff frequency near max mutes the project's audio.
The project's audio can be unmuted by doing any of these: • Reloading the project. • Reloading the effect. • Disabling the effect.
@Sawuare I assigned this to me but maybe you wan't to have a go at fixing this?
How can I reproduce that? Could you please provide steps to reproduce?
- Load a sample in a sample track or load an instrument.
- Add the
LS Filtereffect to what you loaded in the step above. Increase the cutoff frequency to max. - Play the sample or play a note.
@Sawuare I just reproduced that right before you post the comment. :smile:
@Sawuare I assigned this to me but maybe you wan't to have a go at fixing this?
@zonkmachine Sure, but how?
Sure, but how?
We have a super special debug flag when compiling but it's only for Linux and if I remember it correctly you are on Windows, no?
https://github.com/LMMS/lmms/blob/68c85c8e0579827994759573698c5b27f9c71832/plugins/LadspaEffect/swh/util/biquad.h#L105-L118
Here alpha blows up for high frequencies, because omega approaches to π and sn to 0. Here a2 is set to NaN since it is zero times infinity.
Possible workaround is: f->a2 = 1 - a0r * 2.0;
We have a super special debug flag when compiling but it's only for Linux and if I remember it correctly you are on Windows, no?
Yes, I'm on Windows. Is there an alternative?
I got this with the fpe flag. It happened when I tried to open the pluggin controls. In my book that isn't a bad call to powf. If I enter -0,00401606411^0,36787945 in a calculator I get −0,131367367 ...
Program received signal SIGFPE, Arithmetic exception.
0x00007ffff459893f in __ieee754_powf (x=x@entry=-0,00401606411, y=y@entry=0,36787945) at ../sysdeps/ieee754/flt-32/e_powf.c:125
125 ../sysdeps/ieee754/flt-32/e_powf.c: No such file or directory.
(gdb) bt
#0 0x00007ffff459893f in __ieee754_powf (x=x@entry=-0,00401606411, y=y@entry=0,36787945) at ../sysdeps/ieee754/flt-32/e_powf.c:125
#1 0x00007ffff459d1db in __powf (x=-0,00401606411, y=0,36787945) at w_powf.c:27
#2 0x00000000004f08b7 in linearToLogScale (min=88,2000046, max=22050, value=0) at /home/zonkmachine/builds/lmms/lmms/include/lmms_math.h:223
#3 0x00000000004f1945 in AutomatableModel::inverseScaledValue (this=0x19f5d30, value=0)
at /home/zonkmachine/builds/lmms/lmms/src/core/AutomatableModel.cpp:272
#4 0x000000000061818d in Knob::drawKnob (this=0x18dcf00, _p=0x7fffffffb430) at /home/zonkmachine/builds/lmms/lmms/src/gui/widgets/Knob.cpp:445
#5 0x000000000061957f in Knob::paintEvent (this=0x18dcf00, _me=0x7fffffffb810) at /home/zonkmachine/builds/lmms/lmms/src/gui/widgets/Knob.cpp:685
#6 0x00007ffff7122300 in QWidget::event (this=0x18dcf00, event=0x7fffffffb810) at kernel/qwidget.cpp:8533
Yes, I'm on Windows. Is there an alternative?
I don't know how it works on Windows unfortunately. @PhysSong Is it possible to invoke the gnu debugger, gdb on Windows?
Yes. You can run gdb on Windows. However, it will provide less information than Linux.
@PhysSong Is it possible to invoke the gnu debugger, gdb on Windows?
Last we tried this, msys2 was broken with the debug flags. https://github.com/LMMS/lmms/pull/2205#issuecomment-126917960
Increase the cutoff frequency to max.
That is the reason. It will produce a sound with absurd low freq. If you have ambient time, like several hours, the wave-form will dead slowly normalize and sound is re-established Look at the monitor-display, if im right, a horizontal line will be glued to the bottom of the display Could actually be interesting to add a graphic-EQ or SPAN and see what they display in this situation It is not the only filter-plugin that can cause this
@gi0e5b06 No, you're doing definitely wrong math there. That is a little bit long to explain here.
Anyway, the real problem is alpha, which blows up toward infinity. In strict sense, infinity isn't a number. It means it is larger than any number. However, we usually define 1 over infinity to be 0.
And there is a clear fact, 0 * infinity is not defined. That's what we call NaN.
If I enter -0,00401606411^0,36787945 in a calculator I get −0,131367367 ...
@zonkmachine You did a wrong calculation. -a^b is -(a^b)(here ^ denotes power, not the xor operator in C++), not (-a)^b. Such value can be defined using some mathematical techniques, but it never can be a real number. Moreover. there are some ambiguities with that, too.
So (-0,00401606411)^(0,36787945) doesn't make sense in powf() and causes an arithmetic exception. That's a separate issue, I guess.
Edit: //! @brief Scales value from logarithmic to linear. Value should be in min-max range.
It says everything.
wrong calculation. -a^b is -(a^b)
Precisely that error. Doing it again I get an imaginary part. And yes, we're talking floating point operations.
Is there an alternative?
Given how this issue is developing? A friendly advice. Stay away from it. You may not come out of it in one piece.
@gi0e5b06 The problem is:
abs(sn)<10E-10 looks harmless, but it is satisfied only if the frequency equals to the nyquist frequency.
abs(M_LN2 / 2.0 * bw * omega / sn)<0.05 is definitely wrong, since omega / sn is always larger than 1, bw is between 1.0(resonance 0.0) and 0.1(resonance 1.0), M_LN2 / 2.0 is 0.34657359 ... , so it may cause issues.
Unlike most of SWH filters, LS filter can have cutoff near the nyquist frequency(e.g. 0.5 * sampling rate). The usual value is 0.49 or 0.45(at least in other SWH plugins) times the sampling rate. https://github.com/LMMS/lmms/blob/46ef3c6a11e9713c24aa3e9b01c658b2941a58d6/plugins/LadspaEffect/swh/ls_filter_1908.c#L273
It is the same for upstream. @swh Is there any special reason for that?