[Ardour-Dev] "Click of deaf" bug

Pau Arumí pau.arumi at barcelonamedia.org
Fri Jul 16 07:41:10 PDT 2010

To complement Natanael post:
the "brutal explosion" happens random but quite consistently in the
problematic region of the problematic session. Since we are in a room
with 22 Genelec 8040s and 2 subwoofers the problem is quite serious.

As a quick workaround we have implemented a ladspa plugin that detects
such high level situations and plays a low volume sine during few
seconds instead of the high level input. The reason behind playing a
sine is to make the problem evident, so it can not be confused with
another kind of click.

I can provide the code of this ladspa upon request.


El dv 16 de 07 de 2010 a les 10:55 +0200, en/na Natanael Olaiz va
> Hi,
> We found a strange and harmful bug in Ardour, and unfortunately, it 
> looks difficult to reproduce.
> Description: two regions are one just after the other (so, no crossfade) 
> makes a several hundred dBs click when the playhead pass over the 
> intersection: http://imagebin.ca/view/LSvEnz.html
> Some observations:
>      - It happens even without any plugin or automation on the track
>      - If the gain of the track is 0, it doesn't happens. If it's 
> greater, the bug happens and it looks proportional to the track gain.
>      - Related to the previous?: when there is a plugin applied, the 
> gain bug is happening after the plugin process (1 mono track with 22 
> outputs without plugin: all peaks fall -after several seconds- all 
> together, meanwhile 1 mono track with 22 outputs with a spacialization 
> plugin applied: the peaks fall differently because the process)
>      - It looks to happen only when the starting region have the fade-in 
> deactivated (no matter the state of the previous ending fade-out).
>      - When reloading the session, it doesn't happen. But if you move 
> the second region some times, and put it again snapped to the first one, 
> it usually happens again each time you pass over the region intersection 
> until you close the session again.
> We tried to simplify the session removing all the tracks but the 
> problematic one, and still happens. Then we tried to remove clean the 
> unused sources and move the regions to the begining, and we could not 
> reproduce it again...
> Any hint to debug it? Maybe a NaN in the fade-in algorithm?
> Thanks in advance.
> Best regards,
> Natanael.
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