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midi: don't write trailing continuation 0xf0 for SysEx

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Because our midi messages already have a size, we don't need the 0xf0
continuation terminator. Also having the terminator optionally requires
you to check and strip it if it's there.

The easiest algorithm is to check the first byte for start (0xf0) or
continuation (0xf7) and the last byte for end (0xf7) and that should be
enough to process the messages without having to ever stip the last
byte.
This commit is contained in:
Wim Taymans 2026-06-01 13:08:11 +02:00
parent b41d117609
commit 350eb9a041
10 changed files with 52 additions and 35 deletions
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10
doc/dox/internals/midi.dox
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@ -76,23 +76,25 @@ F0 byte and end with a F7 byte. Because of the buffer data length limitations,
it might be necessary to split a MIDI1 SysEx message accross multiple
buffers.
The stategy to implement this is specified in RFC 6295 (RTP Midi) section
The stategy to implement this is inspired by RFC 6295 (RTP Midi) section
3.2. Long SysEx messages can be split up into parts by using the following
start/end bytes combinations:
|-----------------------------------------------------------|
| Sublist Position | Head Status Octet | Tail Status Octet |
|-----------------------------------------------------------|
| first | 0xF0 | (0xF0) |
| first | 0xF0 | |
|-----------------------------------------------------------|
| middle | 0xF7 | (0xF0) |
| middle | 0xF7 | |
|-----------------------------------------------------------|
| last | 0xF7 | 0xF7 |
|-----------------------------------------------------------|
| cancel | 0xF7 | 0xF4 |
-----------------------------------------------------------
The trailing 0xf0 byte can be omitted at the end of continuation packets.
Because control packets have a size, there is no need for a tail
status byte for incomplete first and middle/continuation packets.
They have a regular data byte as the last octet (contrary to RFC 6295).
Nodes that require a complete SysEx message must be able to assemble the
complete message from the parts before processing the message.