Broadcast - Analog TV Test - BAR LINE TIME

Part 3 : Definition of Bar Line Time

Bar and Line Time (Measurement of Bar Level and Line Time Distortion)
References :
1. Walter Fischer Presentation, Analog Television,
2. ITU-T Recommendation J.64 (VITS) and 473 (Test Signals)
3. http://www.hamlet.co.uk/support/Test_signals.htm
4. PAL Systems Television Measurements, Tektronix®, February 2000
5. ITU-T Recommendation J.64

Definition

Colour Bar. See Figure 1.


















Figure 1 : 75% PAL Colour Bar

Consist of Bars which are made up of the traditional seven colours . From left to right they are white, yellow, cyan, green, magenta, red and blue. The colour bar signal is used to align colour monitors and, in systems, to check colour phase and amplitudes using vector monitors. (See also Figure 4a, 4b, 4c and 4d)


White Bar - Plain full white screen. Similar to 700mV Bar. (See Figure 4e)
Luminance Bar – aka Luminance bar amplitude. The luminance bar amplitude is defined as the difference between the level corresponding to the mid-point of the bar (element B2) and the level corresponding to a point immediately following the composite pulse (element F). These points are shown as b2 and b1 espectively in Figure 2. It is to be expressed as a percentage of the nominal bar amplitude (0.7 V for 625-line signals)















Figure 2 : Line 17 for 625-line system
Line Time
Line Time measurement is part of Linear Distortion Measurements.
Base Line Distortion - The base-line distortion is defined as the difference between the levels of the signal at point b7, which is located after the mid-amplitude point of the trailing edge of the bar (element B2) at a distance of 400 ns for 625-line systems (see Figure 2), and at a reference point b1
located before the beginning ofthe staircase in line 17 (see Figure 2). The base-line distortion is expressed as a percentage of the luminance bar amplitude. It is to be measured after the bandwidth of the signal has been limited. The sign of the difference is positive if the signal level at point b7 is higher than the level of reference point b1.

Side notes 1. Source from Walter Fischer Presentation, Analog Television, 30.07.02 Rohde &
Schwarz Munich atv_e1.ppt
Measurement of Levels, Field and Line Time Distortions consists of:
Sync Amplitude (Sync Level)
Burst Amplitude
White Bar Amplitude
Tilt @ White Bar
Base Line Distortion

Figure 2 : Dividing a Frame into Lines

Figure 3 : Black&White Video Signal with Sync

Figure 4a : Three Type of Typical PAL Colour Bars

















Figure 4b : Vector Diagram for Typical PAL 75% Colour Bar
















Figure 4c : 100% PAL Colour Bar

Figure 4d : PAL 75% Colour Bar

Figure 4e : White Bar

Side notes 2. Source from PAL Systems Television Measurements, Tektronix®, February 2000
VM700T Automatic Measurement.
Select BAR LINE TIME in the VM700T MEASURE menu to make bar & line time
measurements. A spectral display and numeric results are provided in this mode (see Figure 5).




















Figure 5 : The VM700T Bar Line Time Measurement Display

The Bar Level are expected to meet typical results as follows:
Bar Level : 700mV
Sync Level : 300mV
Vp-p Sync to Bar top : 1000mV or 1V
Line Time Distortion : <1%

Test setup for Bar Line Time measurements

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