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Resolved NRPN data format

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  1. Max Dobroselsky
  2. Sherlock Holmes
  3. MIDI Specifications
  4. Friday, 21 August 2020
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I have a question about NRPN (non-registered parameter number) data. Can NRPN contain more than one pair of MSB/LSB of data entry? For example, four bytes of data (MSB LSB MSB LSB).
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Given that NRPN is for proprietary use, yes, it's possible to implement a scheme as you suggest if that's what you want to do.
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  1. more than a month ago
  2. MIDI Specifications
  3. # 1
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But if the format of NRPN can be totally arbitrary, is it possible to read them? For example, we can easily read custom meta events since meta events have fixed format. But what if we encountered NRPN in a MIDI file? Is there reliable way to read it? Waiting for NRPN NULL (99/127 98/127)? But, for example, for RPN it's possible to omit NULL since data can be read by definition of RPN. So if we don't know NRPN, it's impossible to read it in general case?
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  1. more than a month ago
  2. MIDI Specifications
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You cannot make any assumptions about NRPN. You can read what's there, but you cannot interpret what you read in any general sense.
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  1. more than a month ago
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Yes, of course we can't interpret NRPN data. But if format is arbitrary, we can't even read data. For example, we see following bytes sequence: 99/xx 98/yy 6/zz 6/rr. What is 6/rr? It's a new NRPN with data of rr, or 6/zz 6/rr together create two-byte value? With RPN we can easily understand where each new RPN starts and ends, even without NULL bytes, just by knowing format of each RPN.
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  1. more than a month ago
  2. MIDI Specifications
  3. # 4
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Usually when both the Data MSB and the Data LSB are used, they are part of a single value, but again, with NRPN you cannot make that assumption.
Are you trying to decide how to present the data in a user interface? What is your goal?
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  1. more than a month ago
  2. MIDI Specifications
  3. # 5
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I'm developing a library to work with MIDI. Now I want to implement parsing RPN/NRPNs. And right now it seems that I have no reliable way to parse NRPN :(
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  1. more than a month ago
  2. MIDI Specifications
  3. # 6
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You have no choice but to expose the individual Data Entry messages. (It's probably safe to combine MSB and LSB if they are sent at the same time.)
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  1. more than a month ago
  2. MIDI Specifications
  3. # 7
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