Limiter bug, continued

Hi,

I created a test session with Ardour which contains "looped" bits of the
part with the cymbal hits which cause the problem. The track also has
the next plugins:

 "Simple amplifier" to make the limiter work
 "SC4" to make the limiter work a little less
  (These two are there to emulate the behaviour of
   jamin before the limiter)
 "Fast lookahead limiter" the jamin limiter

The purpose of this test was to see which plugin causes the
non-deterministic behaviour I've heard happening with Jamin. It
succeeded. If you play through the session you'll hear that the limiter
doesn't work in the same way for the looped regions. It also doesn't
work the same way for the individual looped parts. For instance, playing
the first region a few times in a row reveals very different limiting.

  http://sampo.garageflower.net/jamin/JamBug.tar.bz2
 (btw. the session whines about a missing .wav, don't care about it)

Here's the bomb: Ardour shows the amount of attenuation the limiter is
doing. At the parts where the glitch happens, i saw "nan" clearly
printed on the meter.

I've done the majority of testing with the flag "Stop plugins with
transport" off. When I turned it on I discovered something of interest.
As Ardour stops the plugins at their tracks with the transport, starting
the transport at a different part of the song (in my case, i always
started from the beginning at frame 0) the limiter envelope starts
exactly from where it left. If I've stopped the transport when the
attenuation is at nan, starting the transport again causes a few seconds
of hugely distorted music to come out. The distortion vanishes
gradually, so this is probably the "nan" envelope fading away.
 
-- 
Sampo Savolainen <[email protected]>



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