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5.5 CGMS -A/ID-1
5.5.1 Description and specifications
What is CGMS-A (Copy Generation Management System)?
CGMS-A is a system of multiplexing the copy control information in the vertical sync blanking
intervals, and sending it.
What is ID-1?
ID-1 is a system of multiplexing the aspect ratio information in the vertical sync blanking intervals,
and sending it.
• NTSC, NTSC-M, NTSC-443
• PAL-60, PAL-M
CGMS-A and ID-1 are superimposed onto line 20 (first field) and line 283 (second field). The
CGMS-A and ID-1 waveform consists of the reference bit and 20-bit data. This waveform and the bit
allocation are shown below.
70IRE±10IRE
0IRE
11.2us±0.3us
2.235us±50ns
Reference 1 2 3 4 … 20
Bit no
49.1us±0.44us
Line 20/283
CGMS-A / ID-1
• Bit1-0: Aspect (ID1)
Bit Applications
1 2 Aspect ratio Picture display format
0 0 4:3 Normal
1 0 16:9 Normal
0 1 4:3 Letter Box
1 1 Not Defined
• Bit6-2: Fixed at “0000”
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