Ensemble Designs 9400 3G Test Signal and Sync Pulse Generator - Manual (Page 80)

www.ensembledesigns.com Avenue 7400 and 9400 - Page 80
Model 7400 HD/SD and Model 9400 3G/HD/SD Sync Pulse Generator and Test Signal Generator
SDI
Serial Digital Interface. This term refers to inputs and outputs of devices that support serial digital
component video. This could refer to standard definition at 270 Mb/s, HD SDI or High Definition Serial
Digital video at 1.485 Gb/s, or to the newer 3G standard of High Definition video at 2.97 Gb/s.
SMPTE
The Society of Motion Picture and Television Engineers is a professional organization which has done
tremendous work in setting standards for both the film and television industries. The term “SMPTE’” is
also shorthand for one particular component video format - luminance and color difference.
Single Mode
A Single mode (or mono mode) optical fiber carries an optical signal on a very small diameter (9
micron) core surrounded with cladding. The small diameter means that no internally reflected
lightwaves will be propagated. Thus only the original “mode” of the signal passes down the fiber. A
single mode fiber used in an optical SDI system can carry a signal for up to 20 kilometers. Single mode
fibers require particular care in their installation due to the extremely small optical aperture that they
present at splice and connection points. See also Multi-mode.
TBC
A Time Base Corrector is a system to reduce the Time Base Error in a signal to acceptable levels. It
accomplishes this by using a FIFO (First In, First Out) memory. The incoming video is written into the
memory using its own jittery timing. This operation is closely associated with the actual digitization of
the analog signal because the varying position of the sync timing must be mimicked by the sampling
function of the analog to digital converter. A second timing system, genlocked to a stable reference,
is used to read the video back out of the memory. The memory acts as a dynamically adjusting delay
to smooth out the imperfections in the original signal’s timing. Very often a TBC will also function as a
Frame Synchronizer. See also Frame Sync.
Time Base Error
Time base error is present when there is excessive jitter or uncertainty in the line to line output
timing of a video signal. This is commonly associated with playback from video tape recorders, and
is particularly severe with consumer type heterodyne systems like VHS. Time base error will render a
signal unusable for broadcast or editing purposes.
Timecode
Timecode, a method to uniquely identify and label every frame in a video stream, has become one of
the most recognized standards ever developed by SMPTE. It uses a 24 hour clock, consisting of hours,
minutes, seconds, and television frames. Originally recorded on a spare audio track, this 2400 baud
signal was a significant contributor to the development of video tape editing. We now refer to this as
LTC or Longitudinal Time Code because it was carried along the edge of the tape. This allowed it to
be recovered in rewind and fast forward when the picture itself could not. Timecode continues to be
useful today and is carried in the vertical interval as VITC, and as a digital packet as DVITC. Timecode is
the true metadata.