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Re: core midi time stamping
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Re: core midi time stamping



At 11:50 PM +0100 7/16/05, Bob Lang wrote:
Hi All

It's worth remembering that the "original" MIDI (using five-pin DIN cables) transmits data at around 31250 baud, or 3125 characters per second. Given that a note on or off is 3 bytes (with a possible small saving for running status) then this system allows around 1000 messages per second, or around 1msec per message. Playing 10 notes simultaneously across various channels takes around 10 msecs. Using a MIDI controller keyboard for input and echoing from the computer to an external synth then we get a monitoring delay ("latency") of at least 2 msecs.

USB and FireWire devices may be inherently faster, but we know that the five-pin DIN cable system was fast enough for practical use so I suggest that trying to achieve sub-millisecond timings is unlikely to give any tangible or noticeable benefits to the user. I don't think anyone will notice the improvement, except for the odd pathological situation. And, of course, any improvements you get will be wiped out if the user is still operating with five-pin DIN equipment - and there's plenty of that around.

Actually, we know the the 5 pin DIN cable system was NOT fast enough. The audio perception people have demonstrated that really good drummers can recognize and reproduce timing differences of about 1/3 msec.


As the timing gets better, there is also the issue of phasing between simultaneously triggered notes -- which is predictable with a soft synth and could be predictable with time-stamping and hardware that talks directly to USB (or Firewire, or whatever).
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References: 
 >core midi time stamping (From: david tay <email@hidden>)
 >Re: core midi time stamping (From: Brian Willoughby <email@hidden>)
 >Re: core midi time stamping (From: Herbie Robinson <email@hidden>)
 >Re: core midi time stamping (From: Bob Lang <email@hidden>)



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