external MIDI instrument timing

[dewdman42]

Mts is for MIDI what the audio buffer is for audio.

MIDI still has to ultimately be serialized in the MIDI cable either way.

Historically the reason we had a lot of MIDI jitter has more to do with the fact that the operating system interacted with the MIDI hardware in a sloppy way.

Without mts, what happens is that a host like DP will send MIDI events as they happen to a MIDI device driver. But the OS is taking turns with other tasks, handling the mouse, screen updates, background programs, etc. eventually the Os will give the MIDI device driver it's turn and whatever MIDI events have been piled up will be sent all at once, or serially actually but basically all at once.....not at the original intervals they were intended by the host daw. Because without mts, all of the MIDI events in that interval of time are basically thought by the MIDI driver to be at the same time. So in other words, without MTS, MIDI gets sent and received in clumps, as the OS gives time for handling it.

With MTS, MIDI events are sent to the MIDI driver with some timing information so that they don't go out on the wire in clumps, but spaced apart time wise as intended.

Mts (or not) will not account for the large and consistent latency that we've been talking about here, it's more related to jitter. Mts is a good thing. It's not clear these days which MIDI devices are using it. Motu devices are. Apple coremidi has mts integrated into the api, and dp is merely using that Api now. In years past you needed to use motu hardware with DP or Steinberg hardware with cubase or emagic hardware with logic in order to have some form of mts happening. However now that coremidi includes mts in it, you just need to know that the device and driver is respecting coremidi timestamping. Motu hardware is for sure I know but it's very hard to obtain information about which other interfaces are or aren't respecting coremidi timestamping. When in doubt ask them but the tech support guy probably doesn't even know honestly speaking.

But anyway I feel mts is not really related to the issue we are discussing here which is more about the large and predictable latency and difference between audio and MIDI and the clock. Jitter, which is the timing clumpiness, is what happens without mts.