Program Clock Reference (PCR) measurements have been open to potential misinterpretation from the outset. The key specification, from ISO/IEC13818-1, which became well known throughout the industry, was for a tolerance for generated PCR values of ±500 ns. DVB inherited this and included it as part of its Measurement Guidelines – ETR290. While the guidelines indicated clearly that this measurement was not intended to include any transmission impairments, no real alternatives were available for assessment of PCR jitter. Subsequent operator experience with real systems led to a demand for refinement and greater clarification of PCR measurements – these form part of the revised ETR290, TR 101 290.
This document is intended to provide an overview of these new PCR measurements. It describes why three additional measurements that together provide a very clear and valuable view of overall system performance have supplemented the original measurement.