BLEP Oscillators
I have been reading a little about anti-aliasing oscillators, came across the article linked below, seems a little daunting. Has anyone came across some examples or implementations in Max that helps explain the process? Need help getting my head around it
https://www.metafunction.co.uk/post/all-about-digital-oscillators-part-2-blits-bleps
i am no expert (as you can hardly do that with basic msp objects) but figure 2 in that article shows roughly what the more recent developments are: the idea was that a step - like you have in square waves, saw waves, or sync signals, can be made bandlimited in a very similar way how you would do it for a pulse/spike.
if i am not mistaken, that is what saw~ and tri~, both originated around 2002, already do.
the older and simpler method is when you use additive techniques. for example you contruct a square wave out of partials, and then when the oscillator is played, you simply stop generating those partials wich would exceed half the samplingrate. i do that in my wavetable synths. the trickiest part is when you want to include pitchbend/pitch envelope, the rest is quite simple.
Yes, saw~ and tri~ are both great. If you want to explore something else, or just generally want to do this as a learning exercise, then gen~ is quite capable of doing this. Not the easiest project to take on if you haven't done this before though. There have been some folk working on BLEP in gen~ over the past years too, have a search of the forum archives and see if there's anything helpful there?
I have worked on this in the aim of generating tutorial material for band-limited oscillators in gen~, including BLIT and BLEP and maybe PTR, but it wouldn't be out for a while yet (there's a lot of things going on!)
That's a good idea Roman on stopping the generation of particles exceeding half the sampling rate, How are you implementing this? Using a filter at the Nyquist frequency?
Graham, thanks for the feedback, I believe you recommend me "Digital sound generation" by Beat Frei in a separate post I had on VA Oscillators.
I am going to attempt to replicate this block diagram from that paper in gen~
I will post my efforts here later this week, Maybe you will be able to help me out. Would love to see your tutorial material when it's available.
(Worth mentioning this is a BLIT Oscillator) Not sure which of the two methods is the easiest to implement.
"How are you implementing this? Using a filter at the Nyquist frequency?"
you could call that a filter but actually you would just stop to generate the content.
say you have an additive synth which plays 3 sines at note number 69: 440Hz, 660Hz and at 880Hz.
now you make sure that all partials´ gain will be faded out between SR/4 and SR/2 and that´s it.
for additive synthesis you can do that live - for wavetables you would include that in their generation. (and eventually give one octave "headroom" for possible pitchbend modulation.)