A
SysexMessage
object represents a MIDI system exclusive message.
When a system exclusive message is read from a MIDI file, it always has
a defined length. Data from a system exclusive message from a MIDI file
should be stored in the data array of a SysexMessage
as
follows: the system exclusive message status byte (0xF0 or 0xF7), all
message data bytes, and finally the end-of-exclusive flag (0xF7).
The length reported by the SysexMessage
object is therefore
the length of the system exclusive data plus two: one byte for the status
byte and one for the end-of-exclusive flag.
As dictated by the Standard MIDI Files specification, two status byte values are legal
for a SysexMessage
read from a MIDI file:
- 0xF0: System Exclusive message (same as in MIDI wire protocol)
- 0xF7: Special System Exclusive message
When Java Sound is used to handle system exclusive data that is being received
using MIDI wire protocol, it should place the data in one or more
SysexMessages
. In this case, the length of the system exclusive data
is not known in advance; the end of the system exclusive data is marked by an
end-of-exclusive flag (0xF7) in the MIDI wire byte stream.
- 0xF0: System Exclusive message (same as in MIDI wire protocol)
- 0xF7: End of Exclusive (EOX)
The first
SysexMessage
object containing data for a particular system
exclusive message should have the status value 0xF0. If this message contains all
the system exclusive data
for the message, it should end with the status byte 0xF7 (EOX).
Otherwise, additional system exclusive data should be sent in one or more
SysexMessages
with a status value of 0xF7. The
SysexMessage
containing the last of the data for the system exclusive message should end with the
value 0xF7 (EOX) to mark the end of the system exclusive message.
If system exclusive data from SysexMessages
objects is being transmitted
using MIDI wire protocol, only the initial 0xF0 status byte, the system exclusive
data itself, and the final 0xF7 (EOX) byte should be propagated; any 0xF7 status
bytes used to indicate that a SysexMessage
contains continuing system
exclusive data should not be propagated via MIDI wire protocol.