Originally featured on BroadcastEngineering.com
1/29/2013 9:27 PM
Friedrich Gierlinger, Rico Zimmerman of the German broadcaster’s R&D organization, IRT, talked about the issues around the QC of program files, specifically MXF files. The German, Austrian and Swiss public broadcasters share program files via a WAN. They have regular plug-fests to test interoperability between MXF files created and decoded by different products.
They restrict the essence formats to IMX 50 for standard definition and XDCAM 50 for HD, plus DNxHD 185 and AVC-I 100, with OP1a or OP atom wrapping. Even so, they experienced a 13% error rate in interoperability test in 2012 (in 2011 it was 20% error rate). Many errors were basic MXF file writing errors: non KLV data, invalid BER and UMIDs, and KLV alignment issues. These are basic error, but still exist today. The speakers view was that one vendor may comply with part of the MXF standard, another vendors comply with another part, and incompatibilities arise. Work by the AMWA to create Application Specifications (AS) that constrain MXF should make interoperability within a given AS much easier.
The question was raised “what error rate is acceptable, 10% of files fail, 1%, 0.1%? And how many videotapes failed QC checks, what was considered acceptable reject rates when videotapes were used for content exchange?”
The base MXF standard, SMPTE 377, dates back to 2004, yet eight years later file interoperability is still a big issue. In the IRT tests with a constrained set of MXF files, they still find one in ten fails QC test. I think the end of year report for the vendors is “could try harder”. Sure tape was easier, generally a file recorded on a Sony deck was played back on another Sony product, similarly with Panasonic decks. With file exchange the number of variables is much, much larger, but that is still no excuse for the basic MXF errors that the IRT testers found.