Creative 1212M, 1820M owner manual Smpte Background, Stripe Mode, Time Code, Types of Smpte

7 - Appendix

SMPTE Background

Stripe Mode

This mode is used to record SMPTE time code onto an audio track of another recorder. SMPTE is output when the Start button is pressed in the System Settings menu and begins at the time set by the Start Time setting. MTC is also simultaneously output from the Sync Daughter Card MIDI out. SMPTE and MTC will continue to be output until the Stop button is pressed. See Striping SMPTE.

SMPTE Background

SMPTE time code was standardized way back in 1969 by the Society of Motion Picture and Television Engineers as a way to mark frame numbers on video tape.

Using SMPTE, a particular location can be precisely located by simply entering the appropriate time code number which is expressed in Hours, Minutes, Seconds, Frames and Subframes. This is possible because each frame of SMPTE time code contains absolute location information expressed in digital form.

There are two types of SMPTE time code: Vertical Interval Time Code (VITC), which is used on video tape and Longitudinal Time Code (LTC) or audio time code. VITC is strictly used for video and has the advantage of being able to be read while the video deck is paused. LTC can be recorded on the audio or sync tracks of video tape and can thus be used in audio or video work.

Longitudinal time code is the type of SMPTE used on the Sync Daughter Card. It contains 80 bits of information per frame. An audio SMPTE frame is divided into 80 “bit cells”. A voltage change during a bit cell period constitutes a digital “1” and no change during a bit cell period constitutes a digital “0”. In addition to the location bits, there are user bits that may contain information about tape reel numbers, bits dealing with video information, and a 16-bit sync word at the end of the frame.

FramesFrames Seconds Seconds Minutes Minutes Hours Hours

SMPTE

Time

Code

10	20	30	40	50			60
Start
Frame					Bit		Bit
	80 Bit Cells per Frame			Cell			Cell
						=0

SYNC WORD

70 80

End

Frame

=1

There are four types of SMPTE time code in general use: 24, 25, 30 frame-per-second and 30 drop-frame. In general, you should choose one rate (30 non-drop is common in audio) and stick with it for initial recording and later editing.

Types of SMPTE

Type	Use	Hours	Minutes	Seconds	Frames
24 frame	US Film	00-23	00-59	00-59	00-23
25 frame	Euro. Film + Video	00-23	00-59	00-59	00-24
30 drop-frame	US & Japan Color Video	00-23	00-59	00-59	00-29
30 non-drop	US & Japan B/W Video	00-23	00-59	00-59	00-29

The four frame rates are all straightforward except 30 drop-frame. The 30 df rate came about because the US color video frame rate is actually 29.97 frames/sec instead of 30 frames/sec. This adds up to an error of 108 frames each hour relative to “wall clock”

E-MU Digital Audio System 95