video test

 

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Video Reference

75.75 Color

75.75 Color Bars (also known as 75% reduced amplitude bars with a 75% white reference) is a full field color bars test signal composed of a 75% gray bar (75% amplitude, 100% saturation) and 75% color bars (yellow, cyan, green, magenta, red, blue, and black).

Usage:

Color bars is by far the most widely known video test signal. Color bars are often used to test video levels and chrominance relationships. For example, 100.75 Color Bars is a useful signal to help measure the insertion gain of a device under test. Insertion gain is a measure of the ability to preserve signal amplitudes through a device under test . Errors in insertion gain are visible in the video picture as areas which are too dark or too light. Full field color bars are used in making subjective evaluations and adjustments on color monitors. The waveform view of the black and white bars can also be used as a reference to match the video levels of other video systems equipment.

The VIDI/O Pattern Generator offers a choice of either 75% or 100% bars with an additional choice of either 100% or 75% white bar level for 75% bars. Note that for NTSC transmission applications, chrominance amplitudes for 100% bars can cause distortions and violate NTSC transmission standards, hence the use of 75% bars. Full field color bars are also often recorded at the head (leader) of a video tape and monitored during playback.

Usage Summary: Insertion Gain, Monitor Alignment, Video Levels (WFM), Chroma Level and Phase.

100.75 Color Bars

100.75 Color Bars (also known as 75% bars reduced amplitude bars with a 100% white reference) is a full field color bars test signal composed of a 100% white bar (100% amplitude, 100% saturation) and 75% color bars (yellow, cyan, green, magenta, red, blue, and black).

Usage:

Color bars is by far the most widely known video test signal. Color bars are often used to test video levels and chrominance relationships. 100.75 Color Bars is a useful signal to help measure the insertion gain of a device under test. Insertion gain is a measure of the ability to preserve signal amplitudes through a device under test . Errors in insertion gain are visible in the video picture as areas which are too dark or too light. Full field color bars are used in making subjective evaluations and adjustments on color monitors. The waveform view of the black and white bars can also be used as a reference to match the video levels of other video systems equipment.

The VIDI/O Pattern Generator offers a choice of either 75% or 100% bars with an additional choice of either 100% or 75% white bar level for 75% bars. Note that for NTSC transmission applications, chrominance amplitudes for 100% bars can cause distortions and violate NTSC transmission standards, hence the use of 75% bars. Full field color bars are also often recorded at the head (leader) of a video tape and monitored during playback.

Usage Summary: Insertion Gain, Monitor Alignment, Video Levels (WFM), Chroma Level and Phase.

100.100 Color Bars

100.100 Color Bars, also known as 100% full amplitude bars, is a full field color bars test signal composed of a 100% white bar (100% amplitude, 100% saturation) and 100% color bars (yellow, cyan, green, magenta, red, blue, and black).

Usage:

Color bars is by far the most widely known video test signal. Color bars are often used to test video levels and chrominance relationships. Insertion gain is a measure of the ability to preserve signal amplitudes through a device under test. Errors in insertion gain are visible in the video picture as areas which are too dark or too light. Full field color bars are used in making subjective evaluations and adjustments on color monitors. The waveform view of the black and white bars can also be used as a reference to match the video levels of other video systems equipment.

The VIDI/O Pattern Generator offers a choice of either 75% or 100% bars with an additional choice of either 100% or 75% white bar level for 75% bars. Note that for NTSC transmission applications, chrominance amplitudes for 100% bars can cause distortions and violate NTSC transmission standards, hence the use of 75% bars. Full field color bars are also often recorded at the head (leader) of a video tape and monitored during playback.

Usage Summary: Insertion Gain, Monitor Alignment, Video Levels (WFM), Chroma Level and Phase

EIA Color Bars

Established by the Electronic Industries Association in their EIA RS-189A specification, EIA Color Bars (also known as "split-field" color bars) is a standard test signal with full field color bars (75% amplitude, 100% saturation, Gray (75% white), Yellow, Cyan, Green, Magenta, Red, Blue, and Black) in the upper three-fourths of the display and additional test signals added to the lower fourth. These additional signals include the -I signal, White Flag, +Q signal, and Black and are specifically designed to aid in television transmitter alignment.

Usage: The EIA Color Bar test signal is used in making phase and gain adjustments in color monitors and also used in verifying the accuracy of NTSC encoders and decoders. The luminance component of the test signal offers a convenient gray-scale display which assists in setting color balancing and tracking on color monitors. In transmission applications, the test signal is used for checking transmission levels and detecting the presence of differential gain and differential phase.

Usage Summary: Insertion Gain, Monitor Alignment, Video Levels, Chroma Level and Phase

SMPTE Color Bars:

SMPTE Color Bars is a standard test signal designed to include all the items required to setup, calibrate, and maintain a color monitor. These items include:

  • standard 75% color bars signal comprising the top two-thirds of the display (similar to full-field color bars but without a black bar and with the first bar at 77 IRE instead of 100 IRE)
  • reverse patches of bars below the color bars, from left to right (Blue, Magenta, Cyan, and Gray)
  • a -I signal, a 100% white flag (100 IRE), a +Q signal, and a Pluge pattern at the bottom. The Pluge pattern consists of 3 dark gray strips from left to right, valued at 3.5 IRE, 7.5 IRE, and 11.5 IRE, respectively).

Usage: The color bars portion of the SMPTE test signal is used in applications similar to full field color bars (often used to test video levels and chrominance relationships). Note that the Gray, Cyan, Magenta, and Blue bars all contain an equal blue level content. When setting up a color monitor, contrast and brightness adjustments should always be performed prior to adjusting any color controls. The Pluge pattern is designed as a helpful aid in visually establishing the black level (brightness control) of the monitor. To perform this adjustment, increase the brightness level on the monitor until all the Pluge patterns are just visible. Then adjust the white level (contrast or picture control) of the monitor so that the Pluge pattern looks like a linear ramp (from left to right with each step about twice a bright as the previous step). Then, adjust the brightness level back down so that the two left-most pluge patterns merge in brightness level. The brightness level is correctly set when the two left Pluge patterns disappear into the background and the right pattern is just barely visible. Essentially, your eye should be able to distinguish the difference between the last two Pluge strips, but not perceive any difference between the first two.

The reverse color patches are positioned directly below the color bars and are used in conjunction with the chroma and hue (tint) controls on color monitors. When the chroma and hue controls are properly adjusted, the level of blue content in the bar and color patch below it will be equal matched. These patches are in reverse sequence to the bars to aid in the visual comparison. To perform the procedure, you first need to choose a SMPTE Color Bars with a Blue Filter test signal , or turn off the red and green guns to your color monitor, or choose the Blue-Only mode of your color monitor, if applicable. Then adjust the color (chroma gain) control on the monitor so that the two outer vertical bar/patches match in level. Then adjust the hue/tint (chroma phase) control on the monitor so that the inner two vertical bar/patches match in level.

The I and Q are the color signals of the R-Y and B-Y components used in encoding R,G, and B signals into NTSC video and are used in checking their phase relationships to the other colors when setting up video signals. The 100 % (100 IRE) white flag is a convenient reference in setting video levels and white level.

Usage Summary: Insertion Gain, Monitor Alignment, Video Levels, Chroma Level and Phase

Red Field

Red Field (also known as Red Purity) is essentially composed of a full raster of red with the same specifications as the red bar found from the SMPTE Color Bars test signal. Red Field provides:

  • Chrominance Amplitude = 626.66 mV peak-to-peak (-313.33 to 313.33 mV)
  • Chrominance Phase = 103.5 degrees
  • Luminance Pedestal = 201.74 mV
Usage: The full-field color test patterns (Red, Blue and Green Field) are handy diagnostic test signals to help assess the ability of a device under test (such as a color monitor) to handle the individual primary color video signal components. Often the Red, Green, and Blue test signals are displayed on a monitor while adjustments are made to the yoke magnets of the monitor's tube to ensure proper display. The Red Field signal is often used to help visually detect the presence of noise introduced by a monitor. Our eyes are extremely sensitive to the presence of such noise on a red field.

Usage Summary: General Usage, Chrominance Signal to Noise

Green Field

Green Field (also known as Green Purity) is essentially composed of a full raster of green with the same specifications as the green bar found from the SMPTE Color Bars test signal. Green Field provides:

  • Chrominance Amplitude = 585.28 mV peak-to-peak (-292.64 to 292.64 mV)
  • Chrominance Phase = 240.7 degrees
  • Luminance Pedestal = 344.45 mV
Usage: The full-field color test patterns (Red, Blue and Green Field) are handy diagnostic test signals to help assess the ability of a device under test (such as a color monitor) to handle the individual primary color video signal components. Often the Red, Green, and Blue test signals are displayed on a monitor while adjustments are made to the yoke magnets of the monitor's tube to ensure proper display. The Red Field signal is often used to help visually detect the presence of noise introduced by a monitor. Our eyes are extremely sensitive to the presence of such noise on a red field.

Usage Summary: General Usage, Chrominance Signal to Noise

Blue Field

Blue Field (also known as Blue Purity) is essentially composed of a full raster of blue with the same specifications as the blue bar found from the SMPTE Color Bars test signal. Blue Field provides:

  • Chrominance Amplitude = 443.76 mV peak-to-peak (-221.88 to 221.88 mV)
  • Chrominance Phase = 347.1 degrees
  • Luminance Pedestal = 110.06 mV
Usage: The full-field color test patterns (Red, Blue and Green Field) are handy diagnostic test signals to help assess the ability of a device under test (such as a color monitor) to handle the individual primary color video signal components. Often the Red, Green, and Blue test signals are displayed on a monitor while adjustments are made to the yoke magnets of the monitor's tube to ensure proper display. The Red Field signal is often used to help visually detect the presence of noise introduced by a monitor. Our eyes are extremely sensitive to the presence of such noise on a red field.

Usage Summary: General Usage, Chrominance Signal to Noise

Blackburst Field

Blackburst Field is a full black raster field of video whose level is at 53.57mv = 7.5 IRE. It contains horizontal and vertical sync as well as a standard NTSC color burst packet reference.

Usage: Blackburst is often used to help time and synchronize various parts of a video system and is also used in video noise measurements.

Usage Summary: Synchronization Timing, Luminance Signal to Noise

50% Field

50% Field (also known as Gray Field, or 50% Pedestal) is a full gray raster field of video whose level is at 357.14 mV = 50 IRE.

Usage: The full-field test patterns without any chrominance content (50%, and 100% Field) are handy diagnostic test signals to help assess the ability of a device under test to pass different video levels. Often these test signals are used in conjunction with digital storage oscilloscopes to help identify distortions which may occur over longer time periods.

Usage Summary: General Usage, Video Levels

100% Field

100% Field (also known as White Field, or 100% Pedestal) is a full white raster field of video whose level is at 714.29 mV = 100 IRE.

Signal View:Filename:

S50FLD.BMP
S100FLD.BMP

Usage: The full-field test patterns without any chrominance content (50%, and 100% Field) are handy diagnostic test signals to help assess the ability of a device under test to pass different video levels. Often these test signals are used in conjunction with digital storage oscilloscopes to help identify distortions which may occur over longer time periods.

Usage Summary: General Usage, Video Levels

Multiburst

Multiburst consists of a 70 IRE bar followed by a 10 IRE bar followed by 6 frequency packets of 500 KHz, 1.0 MHz, 2.0 MHz, 3.0 MHz, 3.58 MHz, and 4.2 MHz positioned along the video line, each at 60 IRE peak-to-peak amplitude. The fifth packet (3.58 MHz) is equal to the color subcarrier frequency.

Usage: The Multiburst test pattern consists of 2 bars and 6 different frequency packets along the line of video and is often used for frequency response testing. The idea is to look at the device under test's frequency response by comparing the relative amplitude of each of the Multiburst frequency bursts with respect to one another. An ideal device under test will output all the multiburst frequencies at the same peak-to-peak amplitude. Typical errors in frequency response will manifest as amplitude variations in the individual packets. The common types of errors include:

  • loss of fine details in luminance (due to high-frequency rolloff; i.e. the higher frequency packets are of smaller and smaller amplitude peak-to-peak)
  • noisy edges and sparkles in video pictures (due to high-frequency peaking; i.e. the higher frequency packets are of larger and larger amplitude peak-to-peak)
When testing a videotape recorder, it may be necessary to use a reduced amplitude (60 IRE) Multiburst signal otherwise the high multiburst frequencies may interfere with the FM recording circuits of the videotape recorder.

Usage Summary: Video Levels, Frequency Response

NTC 7 Composite

The NTC 7 Composite test pattern consists of a line bar (125-nanosecond rise and fall time), a 2T pulse (250-nanosecond, half-amplitude duration), a 12.5T chrominance pulse (1.5625-microsecond half-amplitude duration), and a modulated 5-step staircase signal. These signal components are supported with standard synchronizing and blanking signals. The signal is specified in the ANSI T1.502-1988 Standard for Telecommunications. NTC is an acronym for the Network Transmission Committee.

Usage: The NTC 7 Composite signal is primarily used in studio and distribution testing situations. Because it's rise time is too fast, it is not a suitable VITS signal for broadcast transmission usage (Note: the FCC Composite test signal was designed to be used as a VITS since it's rise time is slower). The exact usage is completely specified in the ANSI standard ANSI T1.502-1988. The line-bar portion of NTC 7 Composite is often used in detecting short-time and line-time waveform distortions in transmission service testing. The 5-step modulated staircase is often used for measuring luminance nonlinearity, differential gain and differential phase errors.

Usage Summary: Chrominance-to-Luminance Gain, Chrominance-to-Luminance Delay, Luminance Nonlinearity, Differential Gain/Phase

NTC 7 Combination

NTC 7 Combination consists of a white flag, multiburst, and a 3-level modulated pedestal chrominance signal. These signal components are supported with standard synchronizing and blanking signals. The test signal is specified in the ANSI T1.502-1988 Standard for Telecommunications. NTC is an acronym for the Network Transmission Committee.

The white flag portion consists of an 18 microsecond, 100 IRE bar. The multiburst portion consists of 6 standard multiburst frequency packets (500 KHz, 1.0 MHz, 2.0 MHz, 3.0 MHz, 3.58 MHz, and 4.2 MHz) positioned along the video line, each at 50 IRE peak-to-peak amplitude. The modulated pedestal portion consists of 3 chrominance packets with the same phase, centered about 0 IRE luminance level, with different amplitudes (20, 40 and 80 IRE).

Usage: The NTC 7 Combination test pattern is designed for distribution and broadcast transmission system testing. The exact usage of this test signal is completely described in the ANSI standard ANSI T1.502-1988. The multiburst portion is often used in measuring amplitude response versus frequency. The 3-level chrominance portion is used to detect chrominance-to-luminance intermodulation, chrominance nonlinear gain distortion, and chrominance nonlinear phase distortion.

Usage Summary: Frequency Response, Nonlinear Distortions

Window

Window is a simple, uniform white rectangle in the center of a black background, designed so that the maximum amount of energy is spread in the lower portion of the video passband. The rectangle is a 100 IRE (714 mV) amplitude signal of 26 microsecond duration (about 1/2 the active picture height and width). The rise time from black to white is approximately 150 nanoseconds. The Window pattern occurs on lines 82-200 of field 1 and lines 81-200 of field 2.

Usage: The Window test pattern can be used for checking low-frequency distortions (ringing, smearing, streaking) and for frequency response measurements. It can be used for simple video level checks as well.

Usage Summary: Linear Distortions, Video Levels, Frequency Response

Modulated Staircase

The luminance-only version of the Staircase test pattern is identical to the grey-scale 5 Step pattern (see 5 Step). The modulated Staircase test pattern consists of burst plus a 40 IRE (286 mV) peak-to-peak subcarrier modulated onto each step of the Staircase luminance signal. The luminance-only version of the Staircase test pattern is also known as a Medium 50% Average Picture Level (APL) test signal since it has the 5 Step luminance staircase on each of the active video lines. The GSI VIDI/O Pattern Generator software application has a simple CHROMA ENABLE toggle switch in the PATTERN menu to turn on/off the modulation on the staircase.

Usage: The Modulated Staircase test pattern is useful for differential phase and differential gain measurements (see Modulated Ramp test pattern for further details).The luminance-only Staircase test pattern is used for nonlinearity measurements (see 5 Step pattern for further details).

Usage Summary: Nonlinear Distortions (Differential Gain, Differential Phase, Luminance Nonlinearity Error)

Convergence

Convergence is a regular pattern of white dots and crossed lines with a black background.

Usage: The Convergence test pattern is primarily used for alignment of video monitors to ensure that the red, green and blue electron beams in the tube all illuminate the same location (dot) on the tube's phosphors. If the monitor is not properly aligned, then the lines of the convergence pattern may possess color ghosts or even separate into individual red, green and blue lines or dots, especially near the corners of the monitor. The convergence pattern's regular pattern of white boxes can be used visually detect linearity problems.

Usage Summary: Monitor Alignment, Linearity

Chroma Noise

Chroma Noise is a 100 IRE (714.29 mV) peak-to-peak amplitude red chrominance signal (chrominance phase of 103.5 degrees) modulated on a 50 IRE (357.14 mV) pedestal.

Usage: The Chroma Noise test pattern is used in detecting noise problems affecting the chrominance portion of the device under test's output.

Usage Summary: Signal-to-Noise (Chrominance)

Modulated Ramp

Modulated Ramp is a smooth voltage ramp from 7.5 IRE to 100 IRE, upon which are a 40 IRE subcarrier of 0 degrees phase angle is superimposed. This modulation is of the same hue and phase as the reference burst.

Usage: The Modulated Ramp test pattern is generally used to detect differential gain (saturation) and differential phase (hue) errors. Such errors arise when a device under test's processed output depends on the luminance levels (brightness). When differential gain is present, colors will change in saturation as the picture brightness changes. When differential phase is present, colors will change in hue as the picture brightness changes. The GSI VIDI/O Analyst supports a special automatic measurement mode which automatically calculates differential gain and phase.

Usage Summary: Nonlinear Distortions (Differential Gain, Differential Phase)

5 Step

5 Step is a grey-scale luminance test signal composed of 5 grey-bar steps starting at 0 mV (0 IRE) and increasing to the right in equal steps of 143 mV (20 IRE). It is similar to the luminance signal of the Staircase test pattern as well as the unmodulated 5-step portion of the NTC 7 Composite test pattern.

Usage: The 5 Step test pattern is used to help detect if a device under test can process luminance consistently across the entire range of amplitudes. Typical luminance nonlinear distortions will result in a loss of grey-scale distinctions, which means that detail is lost. To calculate nonlinear luminance error, input the 5-step test pattern into the device under test and then monitor the device under test's output on a waveform monitor (e.g. GSI VIDI/O Analyst). Then, measure the following:

  • V1 = Amplitude Step (IRE) of 1st step
  • V2 = Amplitude Step (IRE) of 5th step
Then, the luminance nonlinearity error, expressed as a % of the largest step is computed as:
  • % Error = 100*(V2-V1)/V2

Usage Summary: Nonlinear Distortion (Luminance Nonlinearity Error)

Pulse and Bar

Pulse and Bar test signal consists of three basic parts:

  • the 12.5T modulated pulse (12.5T sine-squared pulse of amplitude 50 IRE = 357.14 mV, with 3.58MHz modulation, where T = 125 nanoseconds)
  • the 2T pulse (2T luminance-only pulse of amplitude 100 IRE = 714.29mV, where T =125 nanoseconds)
  • the white bar signal (100IRE bar signal of duration 24.6 microseconds with an inverted 2T pulse in the center of the bar).
Usage: The 12.5T pulse portion of the Pulse and Bar test pattern can be used to detect chrominance-to-luminance gain as well as Y/C delay distortions of a device under test. Under ideal conditions, a device under test with zero Y/C delay and no chrominance-to-luminance gain will pass the 12.5T pulse with no distortions (i.e. the bottom baseline of the pulse will be flat).

If a small peak appears on the bottom baseline of the 12.5T pulse, then only chrominance-to-luminance gain distortion is present (positive peak = low chrominance, negative peak = high chrominance). If two symmetrical positive/negative peaks appear on the bottom baseline of the 12.5T pulse, then only Y/C delay is present.

If two asymmetrical positive/negative peaks appear on the bottom baseline of the 12.5T pulse, then both chrominance-to-luminance gain distortion and Y/C delay errors are present. The 2T pulse portion of the Pulse and Bar signal can be used to measure the K-Factor, a measure of linear distortion used in assessing picture quality.

The white bar portion of the signal is used in detecting distortions at low frequencies. If the bar experiences a tilt after it is processes by the device under test , then low frequency distortions are present. If the bar remains flat, then no low frequency distortions are present.

Usage Summary: K-Factor, Y/C Delay, Low Frequency Response, Chrominance-to-Luminance Gain

MultiPaulse

The MultiPulse test signal consists of a series of short modulated pulses of varying duration, subcarrier frequency, and amplitude, specifically:

  • a white flag bar (100 IRE bar signal of duration 5.9 microseconds)
  • the 2T pulse (2T luminance-only pulse of amplitude 100 IRE , where T =125 nanoseconds), and
  • a 25T modulated pulse (25T sine-squared pulse of amplitude 100 IRE, with 1.0MHz modulation, where T = 125 nanoseconds), and
  • four 12.5T modulated pulses (12.5T sine-squared pulses of amplitude 100 IRE with 2.0, 3.0, 3.58, and 4.2 MHz modulation, respectively, where T = 125 nanoseconds).
These signal components are supported with standard synchronizing and blanking signals. The signal is specified in the ANSI T1.502-1988 Standard for Telecommunications.

Usage: The Multipulse test signal is often used in broadcast transmission application since it helps identify group delay errors over the standard video passband. Multipulse can serve as a VITS signal as well. The exact usage of this test signal is completely described in the ANSI standard ANSI T1.502-1988.

Usage Summary: Group Delay, Chrominance-to-Luminance Gain, Chrominance-to-Luminance Delay

 
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derniere mise a jour : dimanche janvier 26, 2003 21:38:01 +0100