Section 3 - Configuring the VM700A
VM700A Option 01 (NTSC) & Option 11 (PAL) User Manual
3-25
The Video Source Identification file contains a series of number and text string
pairs used to identify signal sources in Auto mode. The number is encoded in
binary format onto the line of the frame specified by the Source ID line in the
Measurement Locations file; the default Source ID video line is line 16.
During Auto mode operation, if an encoded ID number is found on the Source
ID line, the VM700A decodes the number and searches the Video Source
Identification file for a matching number entry. If a match is found, the accompa-
nying text string is printed on the line labeled Source ID in the Auto mode
display. If no match is found, the message “Not Found” is printed.
The Video Source Identification file can contain multiple lines. The range for
identifying numbers is 0 to 16383 (14 bits). The text string that accompanies
each number can be up to 20 characters long.
Inserting a Video Source Identification Number. The Video Source Identification
number is inserted using a 148 Insertion Test Signal Generator, a VITS 201 PAL
Insertion Generator, or similar device. Pulses 1 µsec wide and 1 µsec apart
represent binary 1’s. The encoding begins with a start bit (pulse) at the default
location of 26 µsec after the leading edge of sync. (You can change the start
value in the Measurement Locations file, but it should be an even number
between 26 and 52 µsec.) When a start pulse is found, the VM700A checks that
no part of the waveform preceding the start pulse is more than one-half the bar
amplitude. If part of the waveform preceding the start pulse is more than one-half
the bar amplitude, the encoded number is rejected. Encoding always ends with a
stop pulse whose trailing edge is at 57 µsec.
The start and stop pulses are not used in the encoding scheme. There are a
maximum of 14 pulses between the start pulse and end pulse, which are used to
represent a binary number. The pulse following the start pulse is the least
significant bit and the pulse preceding the stop pulse is the most significant bit.
Video Source
Identification (File)
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