On Thu, 21 Mar 2024, Tristan Cacqueray wrote:
I'd like to propose a new package named simple-dsp. I couldn't figure out how to use the existing dsp library, so I made my own version featuring a little GUI to try the code in realtime.
I'd be happy to contribute this work directly to dsp.
The 'dsp' package is pretty old, predating any Vector data type or refined numeric type class hierarchies. I decided to leave it as it is, for educational reasons, since it contains many literal translations of signal processing algorithms from various text books. I have not used most of the contained functions myself.
My goal is to be able to extract sensible discrete values from a sound input at 60 Hz for video production. I implemented low/band/high pass filters to compute 3 RMS volumes, but the values I'm getting are not sharp enough, e.g. the band pass picks the low end. Ideally I would extract the transient events of the percusive sound and the note pitch of the melodic elements.
For a filter that computes lowpass, highpass and bandpass in one go, I use the "universal filter", also known as "state variable filter": https://hackage.haskell.org/package/synthesizer-core-0.8.3/docs/Synthesizer-... You can see running examples here: https://hackage.haskell.org/package/synthesizer-core-0.8.3/docs/src/Synthesi... Frequencies are specified as ratio with respect to the sampling rate, e.g. 440 Hz resonance frequency at 44100 Hz sampling rate translates to 440/44100. For working on storable vectors you would instead use Universal.causal and apply this to Data.StorableVector.Lazy. For very fast processing I have the synthesizer-llvm package, which however depends on the LLVM package in a compatible version. (LLVM-16 currently preferred.) Unfortunately I do not understand your application well, thus I do not know whether the state variable filter is the right choice for your application.