Question

I’m working on midi file format, and I encountered an issue with a file.

Here is the content of my midi sample file where the channel event appears.

[“00”, “b1”, “64”, “00”, “00”, “65”, “00”, “00”, “06”, “0c”, “00”, “e1”, “00”, “40”, “00”, “b1”]

I think this is a RPN event (the part I hilighted).

But I didnt manage to decode this RPN. Why the controller 64 is followed by 2 bytes and 65 too.
How to know if there is only one or two bytes to decode ?

I found this ressources, but can’t find an answer :
http://www.sonicspot.com/guide/midifiles.html
http://www.somascape.org/midi/tech/spec.html#rpns

EDIT :
Later in the same midi file :
[“00”, “b1”, “65”, “00”, “00”, “64”, “01”, “00”, “06”, “40”, “00”, “26”, “00”, “00”, “65”, “7f”, “00”, “64”, “7f”, “00”, “b0”, “64”, “00”, “00”, “65”, “00”]

Answer 1

The second zero value after 64 00 and 65 00 is the delta time for the following message. Every message has delta time before it. Here’s how to interpret your first sample:

time  status  data
 00     B1     64 00
 00            65 00 (running status B1)
 00            06 0C (running status B1)
 00     E1     00 40
 00     B1

Here’s how to interpret the second sample:

time  status  data
 00     B1     65 00
 00            64 01 (running status B1)
 00            06 40 (running status B1)
 00            26 00 (running status B1)
 00            65 7F (running status B1)
 00            64 7F (running status B1)
 00     B0     64 00
 00            65 00 (running status B0)