[PD] midi latency test

[Larry Troxler]

On Thursday 06 March 2003 10:45, Johannes Taelman wrote:
> On Wed, 5 Mar 2003, Greg Rippin wrote:
> > Do MIDI In jacks still use opto-isolator components?  I think they did
> > in the original spec...  The rise- and fall-times could account for the
> > added delay perhaps?
>
> Not possible.
> 1 bit at midi rate is 1/31250Hz = 32 microseconds
> The rise- and fall-time of this optocoupler should be a fraction of that.
>

Really. This is an interesting kind of MIDI "Urban Legend" (qouted because I'm 
obviously misusing the term, since this has nothing to do with whether we are 
urban per se).

It would be interesting to find a story about how this got started. 
 
> I also heard the myth more than once that there is a substantial delay
> between midi-in and midi-thru ports. There is a delay from midi-in to
> midi-out or a 'soft' midi-thru, because the midi-commands are parsed
> before thay're retransmitted. A dedicated midi-thru is just a signal
> buffer.
>
> j#|@

Yep. Agreed. I just wonder if too save a few cents in hardware, if commercial 
synths still typically implement midi-thru as a direct hardware connection? I 
don't know, I should take a look at the manuals for my synths and see if they 
do. I suppose as I think about it, if a synth has a seperate thru and out 
port, then probably very little if anything in hardware costs would be saved 
by emulating the thru port in software.

Larry