I can't figure out why the filter automation I have in the module makes some clicking sounds on the notes. It's on channel 9 and 15. Is this a openMpt bug?
http://dl.dropbox.com/u/1957768/helpmodplug2.it
Drastic cutoff freq changes can make the filter go nuts in several ways indeed, sometimes it even depends on the interpolation algorithm choses in the player options. So yes, in some way it's a bug...
Should I post this bug in the "issue tracker" or is this a known bug that's going to be fixed soon?
It is a known bug, but don't expect it to be fixed soon. I don't even have an idea what causes it. Feel free to open a ticket in the issue tracker, though.
What part in the source code is the filter stuff happening? I want to check it out.
Probably something in fastmix.cpp or mmx_mix.cpp. The fact that the artifacts are different with every filter mode and don't even occur with some of them doesn't really give me much confidence that the fix is simple (i.e. it would most likely involve rewriting the filters for every resampling type, including MMX-accelerated and normal code).
Not sure if this is of any help, but I recall noticing this when I used to work with filters extensively.
When you make an envelope for the cutoff frequency and you have a high resonance filter setting, even if the envelope itself is long enough for a slow progression, you will hear unwanted sound changes at the lower frequencies (on vertical view; everything below around 25% starting from the bottom up)
Why would that be unwanted? It's called resonance. :P The filter just has a 7-Bit granularity, so the steps are obvious, but the resonance is nothing unwanted, on the contrary.
Quote from: Jojo on May 16, 2011, 11:44:54
Why would that be unwanted? It's called resonance. :P The filter just has a 7-Bit granularity, so the steps are obvious, but the resonance is nothing unwanted, on the contrary.
I mean that it looks like the fine progression doesn't occur as if its taking big steps, but that only happens in the lower part of the frequency range.
As said, the granularity of the filter is low. Lower than the interpolated curves in the instrument editor might suggest.
Do you think having a higher granularity like 16-bits etc. would be a possible solution?
Not for your problem. The clicks don't have anything to do with the frequency resolution of the filter.