Picture-quality analysis system delivers
results comparable to human vision

Current picture-quality measurement methods rely on human-viewer trials that take several months to complete and yield inconsistent results. In response to this, Tektronix (Beaverton, OR) has developed the first commercially available picture-quality analysis system, the PQA200, for compressed digital video. The PQA200 system provides objective quality measurements in less than 60 s that are repeatable regardless of the type of impairment present, compression system used, or video material employed.

The PQA200 picture-quality measurement system performs
objectivepicture-quality measurements in less than 60 seconds
with results correlating to human-viewer trials.

The PQA200 assigns a single numeric value to represent picture quality called a Picture-Quality Rating (PQR). This method incorporates Princeton, NJ-based electronic research firm Sarnoff's JNDmetrix technology, which is based on the Just Noticeable Difference (JND) model of human vision. Consequently, the PQR represents qualities that correlate with human-viewer perceptions.

Based on a Windows NT server platform, the PQA200 system uses two compute-engine modules. One module generates test sequences consisting of reference video scenes, while the other compares those sequences to a degraded or impaired scene. Picture quality is automatically measured each time a test sequence is detected.

Multiple digital signal processors perform calculations based on those comparisons and produce two numeric results, the PQR value and a peak signal-to-noise ratio. From these results: the PQA200 identifies impairments or artifacts produced by the system under test, while the JNDmetrix system predicts how human viewers would react to those impairments.

Another tool provided for locating video problems is the JND map, which resembles a photographic negative or night-vision photograph. A totally dark JND map indicates a perfect image whereas a lighter gray map or a map containing white areas indicate problems.

The PQA200 picture-quality measurement system comes with standard 270-Mbyte/s serial component (CCIR 601) inputs and outputs. Option 1 provides analog composite NTSC/PAL video inputs and outputs. The system will be priced at $49,900 with an additional $7,600 for Option 1, and will be available in the first quarter. For further information, contact Tektronix at 800-426-2200 (press 3, code 1054), fax inquires to 413-448-8002.