[LAU] MIDI over wifi on Linux, revisited

Jonathan E. Brickman jeb at ponderworthy.com
Sun Jan 3 14:33:58 UTC 2016

> As others have pointed out already, SLIP is merely used as a means of
> framing packet data (e.g. IP, OSC) on 'unreliable' streams (e.g. serial
> lines). Some clients (e.g. PureData) even use it for 'reliable' streams
> (e.g. TCP).
Got it.  SLIP frames the data, but does not do retransmission.
> First decision you have to take is if you want to go UDP or TCP. As you
> want to do live input, TCP may be too slow on wireless because of
> frequent retransmissions.
> Depending on what you want to do, TCP may just be good enough. Thus
> simply use any of the available OSC and network MIDI libraries
> (RTP-MIDI, ipMIDI, ...) in TCP mode (if the library should support it).
Why, exactly, is existing MIDI/OSC-over-TCP due to retransmissions? 
We're talking about a 31.5 kHz real data stream, why is that necessarily 
slow in response when encapsulated in a wireless connection whose speeds 
start in the megabit range?  Is timeout detection really that long?  It 
is sounding like we need a much shorter timeout for this, something a 
lot more like DNS-over-TCP?
> If you need it to be more responsive, you want to use UDP. As you have
> seen, UDP packets tend to get lost on wireless. The solution is to use a
> means of transport insusceptible to lost packets.
> For OSC, you can use TUIO1 [1] or TUIO2 [2]. They quite elegantly
> circumvent the problem of lost packets by transmitting (almost) full
> state information. There are numerous implementations out there [3].
> [1] http://www.tuio.org/?specification
> [2] http://www.tuio.org/?tuio20
> [3] http://www.tuio.org/?software
> For MIDI, use RTP-MIDI [4] with enabled journaling. The RTP-MIDI journal
> enables clients to recover from lost packets (the journal contains
> critical state information). I am not sure whether there is a readily
> available implementation of RTP-MIDI journaling for GNU/Linux, though.
> [4] https://tools.ietf.org/html/rfc4695
> As a workaround, it may be fun to encode MIDI to TUIO at the sender and
> decode it back at the receiver...
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Will be studying, thanks!

Jonathan E. Brickman   jeb at ponderworthy.com   (785)233-9977
Hear us at http://ponderworthy.com -- CDs and MP3 now available! 
Music of compassion; fire, and life!!!
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