PQA200

Features & Benefits

• Provides Fast, Accurate, and Repeatable Objective Picture Quality Measurements
• Allows Use of Any Video for Evaluating and Optimizing Digital Video Compression Systems
• Replaces Time-Consuming and Expensive Human Assessment with a Reliable Alternative

Applications

• Encoder Design
• Equipment Design
• Equipment and System Evaluation

Picture Quality Analysis System

Introducing the PQA200...the industry's only objective picture quality measurement tool that actually looks at video.

The PQA200 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.

Based on a Windows NT workstation, the PQA200 is both a generator and analyzer of reference test material for testing compressed video systems. Standard inputs and outputs are 270 MBps serial component (Rec. 601). Opt. 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 accurate 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 PQA200, which provides a fast, practical, and repeatable objective measurement alternative to subjective evaluation of picture quality.

How It Works

The PQA200 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 Opt. 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, JNDmetrixTM, based on years of research by the Sarnoff Corporation, the PQA200 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 PQA200 provides 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.