Summary

Since the advent of digital television networks for program transmission, and the introduction of high-efficiency bit-rate reduction (BRR) devices and of other types of digital image processing devices, audiences sometimes complain that the television programs they receive are out of "lip‑sync". Lip-sync errors are generally due to the fact that audio and video are separately processed in the television chain, and processing delays are typically different for video than for the accompanying audio signal.

Recommendation ITU-T J.248 analyses the problem and provides guidance on means to measure lip-sync errors in the context of operational monitoring in television programme transmission chains.