NI Video Measurement Suite

Vertical Blanking Interval (VBI) Measurements

  • Updated2023-08-17
  • 2 minute(s) read

Vertical Blanking Interval (VBI) Measurements

Closed Captioning (CC)

Pattern(s): CC Data Line

Definition: This is a measurement of the “Closed Captioning” (CC) data in a single vertical blanking line of the specified frame (no averaging over multiple lines of frames). It is located on line 21 in each field of 525-line systems (it does not apply to 625-line systems). If the clock run-in and start bits are valid, then all subsequent data bits will be measured and decoded. Each CC line contains a clock run-in, two start bits, and two 8-bit characters, each comprised of 7 data bits and 1 odd parity bit.

Measurement Definition
Run-In & Start Pattern Validation of the clock run-in and start bits as a binary pattern
Clock Start Time Start time of the leading edge of the clock run-in measured at its 50% level
Clock Duration Duration of the clock run-in measured at its 50% levels
Start Bit Gap Duration of the gap between the end of the clock run-in and the leading edge of the third start bit
Clock Levels High and low levels of the clock run-in
Data Rise and Fall Times Rise and fall times of data bits measured between their 10% and 90% levels
Data Levels High and low levels of the data bits
Character 1 The 7-bit decimal value of character 1 and the value and type of its parity bit
Character 2 The 7-bit decimal value of character 2 and the value and type of its parity bit

Wide Screen Signalling (WSS)

Pattern(s): WSS Data Line

Definition: This is a measurement of the “Wide Screen Signalling” (WSS) data in a single vertical blanking line of the specified frame (no averaging over multiple lines of frames). If the run-in clock and start bits are valid, then all subsequent data bits will be measured and decoded. Each WSS line contains a clock run-in, start code, and data bits that define picture aspect ratio, height, and position. PAL data also contains other information. NTSC WSS contains a CRC code.

Measurement Definition
Run-In & Start Pattern Validation of the clock run-in and start bits as a binary pattern
Data CRC Verification of the data CRC
Start Time Start time of the leading edge of the clock run-in measured at its 50% level
Data Rise and Fall Times Rise and fall times of data bits measured between their 10% and 90% levels
Data Width Width of data bits measured between their 50% levels
Levels High and low levels of the data bits
Aspect Ratio Decoded aspect ratio from first data group (4:3, 14:9, or 16:9)
Size Decoded height from the first data group
Position Decoded position from the first data group (525 only)
525-Line Systems:
Word 0 Data
Word 1 Data
Word 2 Data
CRC Data
Decimal values of the 3 data words and the CRC (525 only)
625-Line Systems:
Group 1 Data
Group 2 Data
Group 3 Data
Group 4 Data
Decimal values of the 4 data groups (625 only)

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