MACKIE HDR24/96 - Manual (Page 201)

HDR 24/96
Time Code Reader /
Generator
Distorted
SMPTE In
Regenerated /
Reshaped
SMPTE Out
Small Mixer or Line
Distribution Amplifier
SMPTE In
Gain-Adjusted
SMPTE Out
There are times you may want to offset the position of two devices with respect to each other, but still
keep them synchronized to each other. For example, you may have a tape containing audio that starts
at 18:22:12:00, but you want to record this material to your HDR24/96 starting at 1:00:00:00. In the
HDR24/96, you can set the Time Code Offset parameter to offset the position of the HDR24/96
transport with respect to incoming time code according to the following rule:
Time Code In + Time Code Offset = Transport Position
Offsets can be either negative or positive. The above problem is solved by using a negative offset of
17:22:12:00 such that:
18:22:12:00+ (-17:22:12:00) = 1:00:00:00
In the HDR24/96 time code output always follows the transport position. Nearly every time code-
capable device supports Time Code Offsets.
Similar to the Time Code Offset in the HDR24/96 is the Song Offset. The Song Offset determines
what time code time corresponds to the downbeat of the first measure in Bars|Beats|Ticks display
mode. Instead of affecting the time code input, the Song Offset affects only the display. Using the
same example, a Song Offset of 18:22:12:00 corresponds to BBT 1:1:000. Some devices do not
support display-only offsets like the HDR24/96 Song Offset.
A Word or Three about Pull-Ups and Pull-Downs
Probably no aspect of synchronization causes more confusion than pull-ups and pull-downs. That’s
why we left this subject for last. Simply put, a pull-up or pull-down is the raising or lowering of the
speed of a device above or below the “standard” speed.
The only reason that pull-ups and downs exist is due to the Telecine process by which film is
transferred to video.
Worldwide, films that are destined for theatrical release are shot on film that runs at 24 fps. In the
US, after a film is shot, it is typically transferred to NTSC color video and edited on a non-linear
video editing system. Once the film editing is complete, video work prints are sent out to the various
parties involved in audio post production for the film.
Because NTSC color video runs at 29.97 fps and film runs at 24 fps, there is a non-integer ratio
between the number of video and film frames. To accomplish the transfer, the film is slowed down
by .1% to 23.976 fps to establish an integer relationship of 5 video frames to every 4 film frames.
This slowing down of the film IS the pull-down. The film and video frames are then transferred by
Technical Reference 201