metronome timing accuracy

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Subject: metronome timing accuracy
From: Carsten Bauer (cbauer-@t-online.de)
Date: Wed Jun 25 2003 - 04:29:46 EEST

Hi all,

during playing around I tried to put two metronome signals together:

ecasound -t:300 -a:1 -i:null -el:sine_fcac,880,1 -ea:50 -eemb:60,10
                        -a:2 -i:null -el:sine_fcac,880,1 -eemb:6,1
                        -a:all -o:metro.raw

so one ticks every second, the other every 10 seconds. Interestingly, you hear
signals go out of sync very soon, looking at the file with ecawave shows that
the 6 bpm metronome is a bit slower compared to the 60 bpm one, after 180 sec
it has 1 sec (~0.55%) delay and thus the two signals sound in sync again for
a short while. What might be the reason for this deviation? Which signal can
be trusted more?

(For comparison, the specs of my battery driven digital metronome ascertain a
tempo precison of +/- 0.2 %.)
In fact, in the ecasound example above I thought that no difference at all
would appear because everything is digitally calculated. Wha's wrong, or
what's wrong with my thinking?

When I tried - just for fun - to make the wo signals tick completely synced by
altering the pitch of the 6 bpm signal by 0.55%

ecasound -t:300 -a:1 -i:null -el:sine_fcac,880,1 -ea:50 -eemb:60,10
                        -a:2 -i:null -el:sine_fcac,880,1 -eemb:6,1 -ei:0.55
                        -a:all -o:metro.raw

I get the following:
--------------------------------------------
- [ Controller/Starting batch processing ] ---------------------------------
Warning: DBC_CHECK failed - "impl_repp->lockref_rep == 0", samplebuffer.cpp,
845.
- [ Engine init - Driver start ] -------------------------------------------
Warning: DBC_CHECK failed - "impl_repp->rt_lock_rep != true",
samplebuffer.cpp, 844.
Warning: DBC_CHECK failed - "impl_repp->rt_lock_rep != true",
samplebuffer.cpp, 844.
Warning: DBC_CHECK failed - "impl_repp->lockref_rep == 0", samplebuffer.cpp,
845.
Segmentation fault
-------------------------------------------

OK, it's a weird example :-), but anyway, other, more useful apps of the
envelope modulation might be affected similarly? Or not?

Greetings,
Carsten

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