Old 04-17-2018, 03:06 AM   #1
IXix
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Default Interpreting MIDI implementation charts

Is there some kind of standard for MIDI implementation charts that you need to be aware of to decode them? I get most of the chart I'm looking at but some of it is just totally baffling.

If any kind soul can shed light on notes 1 to 4 (why two byte counts?) and note 5 (huh?) I'd be very grateful (notes start at line 355.)

I'd post the relevant text but it's prohibited in the copyright notice so I'll just post the download link if anyone cares to look...
KORG Kaossilator Pro+ MIDI implementation chart: http://www.korg.com/us/support/downl...ual/0/69/2679/
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Old 04-17-2018, 06:45 AM   #2
goldenarpharazon
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There isn't any "standard" for explaining or documenting SysEx : it is beyond the Midi chart template definition. See https://www.midi.org/forms/midi_chart-v2.pdf. KORG have at least written a spec for these SysEx dumps even if it is very terse, and hence difficult to understand.

MIDI SysEx can only contain (send) bytes containing 7 bits of data, but the KORG device internally stores 8 bit bytes of data. So there is a conversion needed to get all the device data out in a dump in the SysEx stream.

The "Notes 1-4" try to explain this conversion as a resulting size difference with terse arithmetic, and then "Note 5" tries to explain the general encoding/conversion principle between the 7 bit and 8 bit byte length.

If one had access to the Korg device with some knowledge of its internally stored data, and at the same time looked at the actual transmitted MIDI SysEx data (i.e. in a MIDI monitor) alongside the terse Korg specification, then the dump's meaning and structure would gradually become clear(er) as would the spec. Looking at the overall midi.org MIDI standard for sample dumps at the same time might help too.
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Old 04-17-2018, 11:29 AM   #3
IXix
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Quote:
Originally Posted by goldenarpharazon View Post
MIDI SysEx can only contain (send) bytes containing 7 bits of data, but the KORG device internally stores 8 bit bytes of data. So there is a conversion needed to get all the device data out in a dump in the SysEx stream.

The "Notes 1-4" try to explain this conversion as a resulting size difference with terse arithmetic, and then "Note 5" tries to explain the general encoding/conversion principle between the 7 bit and 8 bit byte length.
Thanks, that helps a bit. So the two sizes in notes 1-4 are internal on the left and transmitted on the right? Note 5 is still as clear as mud but maybe if I stare at it a while longer it might start to make sense.
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Old 04-18-2018, 06:44 AM   #4
goldenarpharazon
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Note 5 (the lower diagram) shows all the high order 8th bits (labelled b7) all being packed into an extra 7 bit byte as MIDI data on the wire.

The Note 5 diagram shows 7 bytes of 8 bits being repacked into 8 bytes of 7 bits, which leaves 8 high order bits spare, one in each byte (intentionally unlabelled by the KORG spec author)

The recoding approach makes sense as a simple way to recode the information from 8 bits with minimal (i.e. as simple as possible) programming to encode this at the KORG end, or to reverse the encoding at the MIDI device that receives the dump.
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Old 04-18-2018, 08:45 AM   #5
IXix
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Quote:
Originally Posted by goldenarpharazon View Post
Note 5 (the lower diagram) shows all the high order 8th bits (labelled b7) all being packed into an extra 7 bit byte as MIDI data on the wire...
What I don't understand is how they expect anyone to understand what that diagram actually means! How on earth do you know what it means? It's not exactly self-explanatory is it?

Thanks for your help.
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