What Is Midi Time Code (Mtc) - M-Audio Portman 4x4 Manual

and can be read from audio tracks for synchronization purposes.
The SMPTE Time Code consists simply of:
Hours : Minutes : Seconds : Frames.
Therefore a typical SMPTE time code reading would be:
01 : 25 : 42 : 17
which represents the time 1 hour : 25 minutes : 42 seconds : 17
frames.
The original SMPTE Time Code was Longitudinal Time Code
(LTC). "Longitudinal" means that the code is laid down in a con-
tinuous audio stripe along the length of the tape (longitudinally).
The PORTMAN 4x4/S is designed to write this longitudinal time
code (LTC) as well as read and convert it to MIDI Time Code
(MTC).

What is MIDI Time Code (MTC)?

MIDI Time Code (MTC) is the MIDI implementation of SMPTE.
MTC was first standardized in 1987 as a method of synchronizing
MIDI software and hardware sequencers, as well as drum
machines. Later it was also adopted by digital audio recording
software and hardware manufacturers as a method of synchroniz-
ing to audio and video gear. Interfaces such as the PORTMAN
4x4/S perform the essential task of reading longitudinal SMPTE
from a audio and/or video tape and converting it to MTC for use
by MIDI applications.
MTC implements a special System Common MIDI message that is
sent four times per frame (every quarter-frame). Each of these
"quarter-frame" messages is two bytes long and contains one
eighth of a complete time code value. A unit or program receiving
MTC must receive eight of these messages in order to construct a
the complete time. By the time 8 quarter-frame messages are
received and the complete time is constructed, that time value is
two frames old and it would seem that any synchronized pro-
gram would always be two frames behind. Fortunately, most
sequencer programs add two frames to the received MTC in order
to derive the current time.
As long as a longitudinal SMPTE source is running, time code
may be read. However, what happens when it stops? The LTC is
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