Automated measurements of picture and sound quality of state

Automated measurements of picture and sound quality of state
BROADCASTING | Signal generators
Automated measurements of picture and
sound quality of state-of-the-art TV sets
The R&S®DVSG digital video signal generator supports the development and quality assurance of latestgeneration TV sets and projectors. It is a cost-effective one-box solution that offers outstanding technical
parameters and can be completely remote-controlled when used in automated test systems.
Signals for the development and quality ­assurance
of the latest TV sets
State-of-the-art TV sets with deep-color support provide
enhanced color depth and offer viewers unprecedented picture quality. The devices must also be tested for quality features such as luminance, contrast, color, viewing angle and
motion artifacts (see box on page 3). The R&S®DVSG digital
video signal generator fulfills all the requirements for a highprecision reference signal source. It outputs uncompressed
static and moving video sequences of up to 1080p and PC
resolutions of up to 1920 × 1200 (WUXGA) at a color depth of
up to 12 bit.
A typical setup to measure the described parameters consists
of the R&S®DVSG, which provides the test patterns in line
with standards such as those created by the European Broadcasting Union (EBU), and an instrument for measuring luminance and color (FIG 1).
FIG 1 Typical test setup: The R&S®DVSG digital video signal
generator generates the test patterns specified in the standards. A spectroradiometer is used for measuring luminance
and color.
1
BROADCASTING | Signal generators
FIG 2 Audio analysis at the analog and digital outputs of a TV set
using the R&S®UPV audio analyzer.
The test patterns are, for example, output to the display under
test via the HDMI interface in the R&S®DVSG. A spectroradiometer is normally used for measuring luminance and
color. These devices enable precise contrast measurements
with adjustable measurement angles and are positioned at
a distance that is three to four times the display height of
the device under test. The R&S®DVSG as well as most commercial spectroradiometers can be remote-controlled via an
­external PC.
The R&S®DVSG with its Windows® XP embedded operating
system works like a system controller and can also be used
for remote-control or evaluation applications. Together with
the spectroradiometer, the R&S®DVSG provides reproducible measurement results that exceed the requirements of the
measurement guidelines. The digital adjustment of the amplitude of the entire video signal or of individual video signal
components allows the exact measurement of the gamut in
0.1 percent steps.
Versatile audio generator
New challenges have to be met in the development and testing of modern display equipment, including the requirement
for high-precision signal sources that contain all state-of-theart digital interfaces as well as the appropriate test signals, e. g.
HD signals and moving-picture sequences. The R&S®DVSG
digital video signal generator from Rohde & Schwarz has been
specially designed to meet these requirements. It can also
be used as a pure transport stream player and recorder, an
application for which it is particularly suited due to its extensive signal libraries and excellent price/performance ratio. The
R&S®DVSG is an ideal choice in the development and production of TV displays as well as for servicing and for use in test
houses.
The generator was presented in detail in NEWS 197/08
(pp. 46–49).
Multichannel audio functions, for example in surround
sound systems with up to eight audio channels, are increasingly becoming standard in the consumer electronics sector. Besides comprehensive video signal test capabilities, the
R&S®DVSG offers many audio generator functions via the
HDMI interface. When combined with an audio analyzer such
as the R&S®UPV, the R&S®DVSG can thoroughly test the
audio components of TV sets via the analog and digital outputs on as many as eight channels (FIG 2). The R&S®DVSG
features a sine tone generator that can generate test signals for the measurement of amplitude, total harmonic distortion, crosstalk, etc. It also includes ready-made test signals
for measuring frequency response and lip synchronicity. The
R&S®UPV and the R&S®DVSG have a uniform remote-control
interface in line with the VXI11 standard, which makes an efficient implementation of automated test sequences possible.
NEWS 200/10 2
BROADCASTING | Signal generators
screen resolution, for example. Problems can occur if a device
is operated in a mode that is not available on another device.
To avoid this, state-of-the-art TV sets are provided with a type
of electronic data sheet – the extended display identification
data (EDID) table, which is transmitted via the HDMI interface. It contains information about manufacturer, supported
resolutions and timings, audio and video formats, color and
gamma settings, etc. If a Blu-ray player is connected to a TV
set, for example, the player evaluates the EDID data and configures the optimum output formats. An analysis function in
the R&S®DVSG allows the development and verification of the
EDID contents in the HDMI signal (FIG 3). The EDID can be
stored as a text or binary file to enable further processing or
analysis also via the remote-control interface
FIG 3 The R&S®DVSG offers an analysis function for the extended display
identification data (EDID).
In order to fully enjoy picture and sound especially in consumer electronics, smooth interaction between DVD or Bluray disk players and recorders, amplifiers and TV sets is crucial. However, if the interconnected consumer electronics
devices support different modes, this can be difficult. Take
Summary
The rapid technological progress of TV sets and projectors
places diverse demands on T&M systems. These tasks can be
accomplished only with high-end and automatable measuring instruments. The R&S®DVSG digital video signal generator
from Rohde&Schwarz offers a broad scope of features and is
ideal for handling current and future requirements in development labs and quality assurance.
Harald Gsödl
Basic quality parameters of displays
To assess the overall quality of a display, measurement standards worldwide define a wide variety of measurements.
The most important classic quality parameters are explained
below:
JJ Dynamic range This parameter defines the luminance ratio
of maximum white level to black level, i. e. the luminance
scale that is maximally supported by a display.
JJ Contrast Unlike the dynamic range of a display, which
involves the separate measurement of the maximum white
level and a black level, the contrast is measured simultaneously in a test pattern.
JJ Gamma This parameter defines the electro-optical transfer
function of a display. This function describes the luminance
at a gray level gradually changing from black to white.
JJ Gamut The gamut is the available color space of a display.
It is defined as the color coordinates of the three primary colors red, green and blue; their mixture allows all other colors
to be reproduced.
JJ Homogeneity Another essential display parameter is the
homogeneity of the displayed picture. Displays must always
reproduce uniform luminance and color values at any position on the panel (FIG 4).
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FIG 4 EBU test sequence for measuring display homogeneity.
JJ Angle-of-view
dependence This parameter describes the luminance and chrominance values of a picture depending on the
horizontal and vertical angle of view.
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