[LAD] External midi sync

[Tim E. Real]

On January 22, 2010 07:22:14 pm you wrote:
> On Fri, 2010-01-22 at 18:34 -0500, Tim E. Real wrote:
> > Good, but that would introduce glitches.
> > What if the next sync comes at two or three times as long as the last
> > one?
>
> Say the last sync came 20 ms ago. We guess that the next will be
> something like the same but and devide the next 20 ms seconds in 4
> periods of 5 ms each. Three things can now happen:
>
> a) The next pulse comes very early, perhaps after 10 ms? Dump out on the
> interface whatever was supposed to play in the later, in the last
> periods.
>
> b) The next pulse comes very late, perhaps after 30ms? In that case we
> have have already played everything. There will be slight gap which will
> go unnoticed given the dramatic change of tempo.
>
> c) The next sync comes approximately as expected, perhaps after 19 or
> 21ms? Well, then there is no problem at all :-D
>
> > One simple (slower) tempo change and the rest of the song is out of sync.
>
> No!
>
> > We should not guess, we cannot assume or look ahead.
>
> Yes we can! (Hey, Roland already figured this out back in -85 or so)
>
> > The only solution seemed clear to me: Straight ahead linear real time,
> >  no assumptions of what's to come.
>
> This is soo 1982 ...
Yeah well, so are some parts of some linux apps, eh? He he...
Gee, I thought my newly acquired C64 skills would translate well here.
And what's wrong with my mullet? 
Ok, you've convinced me, there's room for improvement, I'll see if I can
 work it in. Thanks.
Good points. When that late sync finally arrives I can 
 adjust and make up for time lost due to the guess, even if it means 
 some notes will play sooner than expected during that moment, 
 while still regaining sync later.

Anyway it's way better than it was, now it's even usable. Just happy 
 about that. 

> > Really the resolution it is not noticeable, even at 20BPM.
>
> 20BPM is a resolution of 125 ms?? I am now convinced you do not not
> record yourself playing keyboard.
Sure I do. 
I record my KB by turning off external sync in the app so it uses its 
 tempo map for precise note time measurement.  
I sure wouldn't sync the app with my KB as sync master at 20BPM while 
 recording my live performance on the KB !
Looking at my piano roll, I have some 64th notes, and some odd time notes
 here and there. But on playback it sounds great even at 20BPM playback,
 considering, well, it's at 20BPM ! Even if some notes are slightly off. 
Tim.