--- John Rigg <[EMAIL PROTECTED]> wrote: > While we're on this subject, has anyone analysed the > aliasing behaviour > of the LADSPA compressors? This post reminded me of > an article I read > in the AES journal a while back, and a search on > aes.org found it:
I just hacked up a little experiment, by making SC4 output the gain control signal in place of the right channel and using Jaaa. It turns out that we DONT handle this at all! The gain control signal has energy right the way out to the band limit (and probably aliased around it), never mind what happens when that hits the multiplier! Fixing this right means upsampling and adding a lowpass filter to the control loop, then downsampling again. Anyone have a pointer to the latest version of that fast factor of two resampler that was posted here kicking around? Fixing it crude (but probably close enough) means adding a serious LPF at a few Khz in the sidechain just before the gain multiplier.... Note that doing this inherently limits the speed of the attack. The problem is that SC4 is far from the only problematic case, I don't see ANY of the ladspa dynamics plugins getting this right (with the possible exception of the 'Dyson' compressor, and I am not too sure about that one). Regards, Dan (Who is now honour bound to propose a patch), working on it. Send instant messages to your online friends http://uk.messenger.yahoo.com
