MIDI Time Stamp

[wackazong]

Hi,

in all MIDI Monitors, also in MIOS Studio, there is a "MIDI timestamp" or "MIDI Time Stamp". On the web I could not find what the format of that timestamp is. Can somebody explain that to me? How do I see whether the MIDI Event that I receive contains a timestamp? It should come before the status byte, but how is its format defined? I looked at a lot of "MIDI spec explained" sites, but I did not find an answer anywhere.

Thanks, ALEXander.

[stryd_one]

There's no timestamping in midi, that's just the time that the PC counted when it's received/the time when it sent it.

[nebula]

There is a timestamping capability for USB MIDI interfaces, in which the messages are sent to the interface shortly before they are actually to be sent out.  The protocol calls for a timestamp, and when that time occurs, the interface sends out the message.  This is to improve MIDI timing.

MIDI timecode is essentially hours/minutes/seconds/frames encoded over MIDI.  It is used to synchronize devices like DAWs, tape decks, video ... It should not be confused with MIDI clock, which is simply a byte sent out 24 times per quarter note, and its rate will vary depending on the tempo of the music - it's used to sync up stuff like drum machines and sequencers.

[stryd_one]

There is a timestamping capability for USB MIDI interfaces, in which the messages are sent to the interface shortly before they are actually to be sent out.  The protocol calls for a timestamp, and when that time occurs, the interface sends out the message.  This is to improve MIDI timing.

Yeh, less jitter, at the expense of latency...

But.. I think you'll find that the timestamping is not part of the USB MIDI protocol itself, and as such, not all drivers support it. For example in windows, the drivers using WDM can have the messages timestamped, but they can also just be fired out, FIFO style. Non-WDM USB MIDI drivers (and those not implementing all the WDM capabilities) don't get the timestamp from the app, so the timestamping has to be generated in the driver and decoded by the interface hardware, and when that is done, it's a proprietary solution. In fact, most drivers seem to make the timestamping, if it is even passed to the hardware, a proprietary implementation. If this weren't the case, almost all USB midi drivers would have comparable timing, and it'd be good. Alas that is not the case :(