Antex Electronics StudioCard AV Pro, StudioCard 2000, & SC-22 - Manual (Page 119)

C h a p t e r 6 V i d e o
6-10 Antex StudioCard Copyright © 1997
Video The video input provides a connection for incoming composite
video to a horizontal sync extractor circuit and a vertical interval
time code (VITC) reader. The horizontal sync extractor extracts
a sync pulse from the video signal and then performs a
frequency multiplication to create a clock that can be used as a
reference for the sample clock generator. The VITC reader,
which meets SMPTE VITC specifications, reads VITC frame
data and then stores it in a receive buffer . The DSP reads a
buffer when it is full and stores it in a mailbox register for the
host. If desired, the DSP will convert the VITC frame data into
MTC and merge the resulting message into the MIDI input data
stream. The DSP controls the frame rate, format (NTSC or
PAL), and video scan line of the reader.
The composite video signal available at the video output is
derived from a VITC generator that is capable of inserting a
burned-in time code window. The DSP controls the generator’s
frame rate, format, VITC video line, and sync source. The DSP
also supplies frame data from the host or, when jam sync
mode is selected, data is derived from the LTC, VITC, or MIDI
input. The burn-in window can be enabled or disabled and
displays time code from the either the VITC or LTC generator
or from the LTC, VITC, or MIDI input. When the VITC
generator and burn-in window are disabled, the video output
acts as a video feedthrough of the video input.