Jörg Houpert, head of technology, Cube-Tec International explains what next level auto QC and media correction means.
The move to file based workflows has dramatically increased efficiency in media production chains.
Material eXchange Format (MXF) is the predominant exchange format of professionals. MXF is highly flexible and covers a huge variety of supported essence formats.
This flexibility has spawned a massive rise of interoperability issues and this situation has not changed significantly within the last five years.
Classical QC products can help MXF experts to detect the root cause of interoperability reasons.
But this does not make damaged files work. MXF experts are a rare resource in nearly all operations, so minimising their workload frees-up the experts for innovative work instead of hands-on MXF troubleshooting.
I have a question - is this a familiar scenario in your company?
Every MXF file will be sent through a transcoder farm, before being transferred to the playout server, just to make sure it will not crash live on air.
This happens because it is assumed that, during this procedure, erroneous files will be rejected or corrected by the transcoder - and no errors will occur during playout. How wonderful that would be!
But this is what really happens when you insert a transcoding step in the production chain: incoming files will be unpacked out of their MXF container, de-multiplexed, decoded, re-encoded again, newly multiplexed and played out with a new MXF container.
Adding this procedure to the workflow can in fact add unexpected problems, such as decoding errors that are added to the file.
It becomes exceptionally nasty if macroblock errors are ‘burned’ into the picture sequence.
With automated QC systems, those burnt-in errors are far harder to detect than the original error in the codec bit-stream.
Other errors like missing subtitles, wrong audio channel alignment, illegal video levels, picture sequences with so-called ‘video freeze’, hard-to-detect re-encoding artefacts can also be newly created.
The only thing you can be sure about is the loss of picture quality, as transcoding is a lossy procedure. It usually requires a manual full visual verification.
If you want quality control without transcoding, a specialised QC and correction process is the only way in getting that task done properly.
This content was first published at IBC 2016.
The views expressed are those of the author.