LFO problems

trogluddite · 24 May 2012

I'm guessing you are referring to the stability in time (i.e. synchronising to sample clock/tempo etc.).

As LFO's are dependent on counters, it will depend on the accuracy of the maths that is counting time - and any errors will change slightly with frequency. In SM, most numbers are 32bit floats, and these will be less accurate than the 64bit "double precision" floats used by some software. However, over the course of a whole song, the drift will be very small - you would have to compare the waveform phase with a known "accurate" wave to really see much difference. And, as all music software uses the favourite algorithm of the programmer, who is to say which one is more 'right'. For tempo synchronisation, the best way is to lock the LFO to the PPQ signal from the VST host (if search for 'PPQ' there are several examples) - that makes the host the 'Master' for timing, and will ensure that an LFO stays sync'ed to the bars and beats of the song.

As for CPU, there is no difference in ''priority' for LFO's compared to other audio - all of the streams (blue/white) in your plugin will run on the same CPU thread, and are considered part of the same 'process'. This will usually have quite high priority, as the timing is very important in order to avoid problems for the soundcard driver (in contrast, graphics etc. will be on a lower priority thread, so that they cannot interrupt the sound).

pall · 24 May 2012

Thanks Trog! I wanted to be sure if a LFO is suitable to build a sequencer. I made an impromptu, and I would like to know if is in right direction. But here in the General section seems cannot attach schematics. I start a thread to the Example section?