PQA300 Tektronix TV Equipment Used

System Components

• Mainframe: Tektronix manufactured in portable cabinet enclosure with handle
• Processor: Two 400 MHz Pentium II processors
• System Memory: 256 MB
• Real-time Clock: Real-time clock/calendar with a resolution of 1 second or less
• BIOS: Phoenix BIOS, Y2K compliant, field upgradable.
• Bus: 32-Bit PCI.
• Nonvolatile Storage: Floppy Disk Drive: Standard 3.5 in. PC compatible floppy disk drive; 1.44 MB high-density double sided (2HD)
• Network Connection: Ethernet
• Mainframe Interfaces
• One loop-through Ethernet port
• One bi-directional RS-232/RS-422/RS-485 port
• One parallel port (printer)
• One hot-pluggable keyboard port (on the rear panel)
• One hot-pluggable mouse port (on the rear panel)

Safety-Designed and Tested for Compliance with:

• IEC 61010–1.
• CAN/CSA C22.2 No. 1010.1.
• ANSI/ISA S82.01
• EN61010-1
• 73/23/EEC.
• 93/68/EEC.

Applications

• Encoder Product and Component Design Verification
• Transmission Equipment and Systems Evaluation
• Picture Quality Video Content Verification and Analysis at the Program (Video) Layer

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.

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 is 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.

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.

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.

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.

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.

The PSNR 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.