Applications:
- Encoder Product and Component Design Verification
- Transmission Equipment and Systems Evaluation
- Picture Quality Video Content Verification and Analysis at the
Program (video) Layer
Picture Quality Analysis System
Introducing the PQA300... the industry's leading objective picture quality
measurement tool based on the Emmy Award-winning PQA200 platform.
The PQA300 analyzes picture quality with repeatable, objective measurements
that directly replicate subjective human visual assessments. These measurements
provide invaluable information for engineers working to optimize video
compression without compromising picture quality.
The PQA300 is both a generator and analyzer of reference test material for
testing compressed video systems. Standard inputs and outputs are 270 Mb/s
serial component (Rec. 601). Option 01 provides analog composite NTSC/PAL inputs
and outputs.
Compressed Video Requires a New Method of Testing
The best measure of any analog or digital television system is the viewer's
satisfaction with the image received. Traditionally, the quality of analog and
full-bandwidth digital video systems has been measured indirectly by measuring
the distortions of static test signals.
Compressed television systems, however, pose a far more difficult measurement
challenge. Picture quality in these systems changes dynamically based on the
data rate, picture complexity, and encoding algorithm employed. The static
nature of test signals does not provide true characterization of picture
quality. Natural test scenes that are far more complex than test signals must be
used to stress the capabilities of compressed video systems.
Until now, subjective testing using human viewers has been the only available
method for evaluating compressed video systems. But, while useful for
establishing academic reference data, subjective testing has been impractical
for operational, manufacturing, and troubleshooting applications — until the
development of the Tektronix PQA300, which provides a fast, practical, and
repeatable objective measurement alternative to subjective evaluation of picture
quality.
How it Works
The PQA300 measures a 2-second portion of a 5-second video test sequence. The
video test sequences may be downloaded from supplied CD-ROMs or recorded from
your own video, and played out to the system under test. While serial digital
interfaces are standard, analog composite and S-Video (Y/C) interfaces can also
be accommodated with the addition of Option 01.
| The output of the system under test is then stored and analysis performed
with DSP-accelerated hardware on the 2-second sequence. The measurement results
in a single numeric value of picture quality called Picture Quality Rating (PQR).
Utilizing a human vision system model, JNDmetrix, based on years of research by
the Sarnoff Corporation, the PQA300 analyzes the three necessary dimensions for
evaluation of dynamic and complex motion test sequences: spatial analysis,
temporal analysis, and full-color analysis. |
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| In addition to reporting the Picture Quality Rating, the PQA300 provides
PSNR-values and an animated map whose intensity is related to the
perceived differences between the original and captured image. This
provides invaluable information for evaluation and optimization of
digital video compression systems. |
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| The PQA300 provides Results
Summary, Graph Files, and PSNR Difference Maps for in-depth, detailed
analysis to help you evaluate your equipment design, transmission system
evaluation, or conduct your picture quality content verification and
analysis at the program (video) layer. |
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The Results Summary
The results summary screen shows a frame-by-frame summary of the test
results, PQR, and PSNR scores for both the reference and test video. |
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The Graph File
The analysis performed in the graph screen allows the user to select any
of the results in much greater detail. For example, as you go to the PQR
graph, you will be able to see the distribution of the scores on a
frame-by-frame basis and identify individual frames that may be of
interest based on the scores. |
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The SNR Difference Map
A visual illustration of the differences between the reference and test
video is displayed on this difference map. By highlighting the
dissimilarities in the content, it visually illustrates the impairments
that were imposed by the equipment on the resulting video |