Midi Merge Technique? (Jitter)

[Philip Pilgrim]

I guess you could design a windowing circuit where the incoming MIDI
data's edge is detected and then a dT transpires before checking the
bit. If this dT was ANDed with a free running stable clock on the
receiver then jitter would be eliminated. This removes edge timing
recovery from the incoming signal and sort of makes the circuit a simple
edge detector with timing and bit regeneration.

      ___________
     /           \ 
    |             |
____|             |__________
incoming "sloppy" Midi

    |<-dt->|win|
    
     |      |      |
     |      |      |
_____|______|______|____
Clk
             ______
            |
            |            
____________|
reconstructed MIDI data



Philip


Batz Goodfortune wrote:
> 
> Y-ellow Y'all.
>         it just occurred
> At 02:43 AM 01/23/00 +0100, Magnus Danielson wrote:
> 
> [bobbit]
> 
> >MIDI clocks are just specified as being relative in frequency and not much is
> >being said about jitter. Nobody really thinks about jitter since it is an
> >asynchronious protocol which by nature has varying delay. Jitter is the
> >property of some cyclicly reoccuring event, and this is exactly what an
> >asynchronious protocol isn't. If you try to send contious events over it you
> >may talk about jitter thougth. You could also possibly talk about jittered
> >delay as you send some message in and await it to pass through some system.
> >There is the cyclic event in your messurement and not in the system.
> 
> There is one thing that all of us have overlooked as far as jitter is
> concerned. Including myself until now. And that is, the receiving end, if
> it's any good, has to have a PLL or fly-wheel circuit. Whether that be
> software or hardware. And what this does is overcome Jitter.
> 
> Often called a flywheel circuit because of it's similarities to a big heavy
> flywheel with a lot of momentum. It takes a lot to change the speed over a
> long time. Which means the speed is pretty damn constant at the receiving
> end. regardless of how much jitter there is. (to a point of course)
> 
> And of course. The reaction time of the PLL is set up so that a fast rate
> of change (accellarando/decellarando) can occur but jitter and even missing
> pulses can be circumvented.
> 
> So I guess, as long as the jitter isn't so bad that it represents an actual
> tempo change, there isn't going to be much of a problem.
> 
> Hope this helps.
> 
> be absolutely Icebox.
> 
>  _ __        _
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