St. Zappa:

“…Baby sna-a-a-a-kes….
…They live in a ho-ho-hole (tiny hole) that is usually empty
(Usually empty…) tiny too!
They live by a co-co-code (Dit-dit-dit) that is usually SMPTE
Which stands 4 :
Society of Motion Picture and Television Engineers…”

SMPTE is indeed the society’s name, as mentioned. SMPTE TIME CODE is the American standard 4 time codes running @ 30 frames per second and 29.97 fps (drop frame), used 4 the NTSC video systems. In that case the TC will b nicked “SMPTE”.

At lower rates, the EBU ( European Broadcasting Union) standard is used (25 fps, 4 PAL video systems). So the TC will b nicked “EBU”.

24 fps rate (film) is also supported.

Each TC “frame“ includes a time address (hour, minute, second, frame) and other bits referring 2 user data, tape direction (sync word) etc.

VITC (Vertical Interval Time Code) is the time code recorded ACROSS the videotape, between any 2 frames of picture. This way the rotating video head can read the TC even when the tape is paused. Each frame is 90 bits (sub-frames) long.

LTC (Longitudinal Time Code) in the TC recorded ALONG audio tracks. TC cannot b read when tape is paused. Each frame is 80 bits (sub-frames) long.

A digital code is used, recorded as a Bi-phase Mark signal, so it can b read regardless of phase. Phase may b corrected by a special bit (Bit 27, if my aging memory is correct…).

The intelligent reader may have noticed that sync resolution can b as tight as 1 frame divided by 90 or (1 sec / 30 frames / 90 bits) = 0.37037… mSec.

At these tight resolutions, slaving a computer 2 an analog machine will copy the machine’s wow and flutter (speed variations) 2 the sampling rate clock, crapping errors all over the place. So slaving the machine will result in a better sound.

Since MIDI is a digital code too, the MTC (Midi Time Code or Matai Tikne Cvar) format carries the time code information embedded within the MIDI signal so these data can b transmitted 2 musical instruments, computers etc.

Since MTC data r long, sending them may slow ur MIDI down.

Cool handy little tools.

St. Zappa: (cntd.)

“…Maybe I think
That is what keeps them in sync
They’re wet and they’re pink
I think I’ll give’em a, give’em a, give’em A DRINK! “

Peace,

Zooot.