NTIA Technical Memorandum TM-10-463

A Full Reference (FR) Method Using Causality Processing for Estimating Variable Video Delays

October 2009

Stephen Wolf

Abstract: Digital video transmission systems consisting of a video encoder, a digital transmission method (e.g., Internet Protocol – IP), and a video decoder can produce pauses in the video presentation, after which the video may continue with or without skipping video frames. This time varying delay of the output (or processed) video frames can present a challenge for some video quality measurement systems. The reason is that time alignment errors between the output video sequence and the input (or reference) video sequence may produce measurement errors for full reference measurements like Peak Signal to Noise Ratio (PSNR) that greatly exceed the perceptual impact of the time varying video delays. This document presents a Full Reference (FR) method for estimating variable video delays. The algorithm can optionally execute a sophisticated causality processing algorithm to improve the robustness of the delay estimates. The delay estimates produced by this algorithm can be utilized by a FR quality measurement system to remove variable video delay as a calibration step before computing the quality measurement.

Keywords: calibration; causality; delay; dropped frames; Full Reference (FR); pausing; skipping; video quality

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