HP 8591C User Manual page 289

Test Descriptions
Color Test Descriptions (Chromalluma Delay Inequality, Differential Gain, Differential Phase)
The composite test signal (FCC, NTC 7) is automatically selected. The
analyzer then tunes to the luminance component and switches to 0 Hz span.
Video averaging is performed and the center of the luminance component is
found and converted to time.
Next, the analyzer tunes to the chrominance component and performs video
averaging. The center of the chrominance component is found and converted
to time. The time difference between the two components is then computed.
Since the analyzer measures absolute time, an offset of 170 ns is added to the
result so that it will agree with tests done using a demodulator with sound
trap in (170 ns of delay,) and the result will be shown relative to the FCC
required pre-correction. See 'fable 8-2.
Table 8-2. Comparison of CLDI Measurement Values
Relative to FCC Required
Pre-Correction
Absolute
8-36
- 1 7 0
- 3 4 0 - 1 7 0