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Re: It cannot be done under OS X !!
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Re: It cannot be done under OS X !!


  • Subject: Re: It cannot be done under OS X !!
  • From: Kurt Revis <email@hidden>
  • Date: Fri, 26 Mar 2004 11:38:36 -0800

On Thursday, March 25, 2004, at 11:47 PM, Cyril Blanc wrote:

TC Helicon post an update for the Voice One. This update only work on PC.
Complaining about that I have receive the following answer:

.....
"This is why: the sysex-file containing the software update is actually not
a
sysex-file, but a file containing DSP code with a sysex-header. The file
has
to be sent without interruptions of any kind from the computer to the
VoiceOne
for the update to work.
Because of the way MIDI is implemented on the Mac -- in Windows it is
different -- the data is split up into tiny sysex packets during transfer,
thus interrupting the upload."
So you see, this is not really a matter of Sysex, but a matter of the
implementation of Sysex in the MacOS - and - the way the
hardware-architecture
is designed on the VoiceOne.
Therefore there are only two solutions for resolving this:
1. Apple changes their OS implementation.
2. We redesign the VoiceOne hardware.

Their statement that "the data is split up into tiny sysex packets" is very odd. There is no notion of "packets" at the MIDI level, just a stream of bytes.

So even if things are packaged up into smaller packets in the computer, or in the communication between the computer and MIDI interface, it shouldn't make any difference at all when it finally gets to the device.

It sounds like they are saying that the Mac puts longer or shorter pauses between individual bytes of sysex, in a different way than the PC does. This is certainly possible -- I haven't sat down with an oscilloscope to look at it. But as far as I know, the MIDI spec does not specify absolute timing for individual sysex bytes. As long as the pauses are within reasonable bounds, their hardware should be able to deal with it. But apparently their hardware can't do that, even though hundreds of other MIDI devices (some more than fifteen years old!) can.

But that's just my initial guess. It's hard to say for certain without (1) actual data about the sysex byte timing, on PC and Mac, and (2) a look at the MIDI spec.

--
Kurt Revis
email@hidden
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  • Follow-Ups:
    • Re: It cannot be done under OS X !!
      • From: Neil Johnson <email@hidden>
References: 
 >It cannot be done under OS X !! (From: Cyril Blanc <email@hidden>)

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