Remove interpolation of IIR filter coefficients #1345
Conversation
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Very good to see you are already trying to put this into Fluidsynth. I'm not sure what IIR means or what that does to the filter. And I know even less on what fres_mod changes to the cutoff frequency but I'm sure you got this down to a tee. As you can tell, at this point I'm pretty much lost on what all this means but glad you were able to find the issue and stop anymore clicks and pops to the sound as well. Wow this seems like it will not be easy to find what is behind the problem at all then. Sure, on stuff like this it will be your call to do what you assume is the best way forward. So you had to remove it. I just listened to both samples and find it hard to hear that much of difference, in other words, to me each sample has clicks and pops, but the second has barely any less, why is that ? |
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You need to listen till the end. The first clicks appear in DF2.ogg after 22 sec. |
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Yes I'm able to hear the clicks in DF2.ogg but also get clicks in DF2-nointerp.ogg as well |
* master: (33 commits) Remove interpolation of IIR filter coefficients (FluidSynth#1345) Add OS/2 KAI audio driver Fix behavior of volume envelope delay phase Fix chorus when compiling with single precision (FluidSynth#1339) Update docs about XG bank selection logic Fix a few compiler warnings Fix linkage against gobject Fix mixed declaration Log NRPNs in verbose mode Update documentation of synth.device-id Access to synth->bank_select not guarded by mutex when processing command line options: -o setting=value, the value is converted to UTF8 review findings Documentation updated (settings, about utf-8 encoding) C++ example updated drivers: winmidi,waveout and dsound using utf8 options Unicode support enabled in CMake script and CLI utility Fixed wasapi driver; encode device names as CP_UTF8 Solves FluidSynth#1322 Fix an import library is treated as a static library on OS/2 (FluidSynth#1321) Bump the github-actions group with 2 updates Keep GitHub Actions up to date with GitHub's Dependabot Minor fixups for MSYS2 CI (FluidSynth#1317) ... # Conflicts: # CMakeLists.txt
During implementation of #1342, I found the IIR filter producing strange cracks and clicks. I haven't done a deep investigation but it seems that this was caused by big and frequent changes of the cutoff frequency by
fres_mod.I found that the clicks were produced by the code that interpolates the filter coefficients. I.e. setting
if(dsp_filter_coeff_incr_count > 0)toif(FALSE)didn't cause any more clicks.Without a deeper investigation of the numeric logic I don't know how to fix this. Yet, I don't think this justifies the more complex logic, and therefore I'm suggesting to remove that interpolation logic.
Attached is a ZIP with two audio samples. DF2.ogg (Direct Form 2) is the filter as implemented before this PR. DF2-nointerp.ogg is the same filter without any interpolation.
filter-coeff-interp.zip