Sysex messages containing bytes greater than 127

[asimilon]

I think it would be flaky at best; it wouldn’t be beyond the realms of possibility that a particular synth might not even really check for F7 as the end marker, but assume that the MSB being 1 is the end of the SYSEX data.

Found this in the “File Dump Data Packet” section of this document

Encoding of data :

The 8-bit file data needs to be converted to 7-bit form, with the result that every 7 bytes of file data translates to 8 bytes in the MIDI stream.

For each group of 7 bytes (of file data) the top bit from each is used to construct an eigth byte, which is sent first. So :

AAAAaaaa BBBBbbbb CCCCcccc DDDDdddd EEEEeeee FFFFffff GGGGgggg

becomes :

0ABCDEFG 0AAAaaaa 0BBBbbbb 0CCCcccc 0DDDdddd 0EEEeeee 0FFFffff 0GGGgggg

The final group may have less than 7 bytes, and is coded as follows (e.g. with 3 bytes in the final group) :

0ABC0000 0AAAaaaa 0BBBbbbb 0CCCcccc

so to be sure you should just encode any 7 bytes of 8-bit data into 8 bytes.