The UK television industry is adopting a common standard for the delivery of television programmes as computer files rather than on videotape, and today is .
"1st October 2014 will be the date by which all UK broadcasters will begin receiving programme deliveries as files."
That might sound fairly simple, but it's taken several years of concerted, collaborative effort across the industry, led by the (DPP).
At this year's IBC, that some products had achieved certification having successfully completed testing. We've been a key part in the machine to make this happen and this post explains some of our contributions to the revolution that is file based delivery.
The file format
These aren't ordinary video files like those that your mobile phone or domestic camcorder might produce. Just as the tape formats used in the broadcast industry were specially tailored to our needs, so too are the video files. We've been involved in developing the standards for these files for over a decade, the most recent of which is the Advanced Media Workflow Association's . This constrains the broad capabilities of MXF (Material eXchange Format) to a subset relevant to programme delivery. The full title of the file format to be used for HD programme delivery is "AMWA AS-11 UKDPP HD Shim". There's also a "UKDPP SD Shim" but we'll focus on HD files here.
The headline features of AS-11 DPP HD files are:
- 1080i/25 AVC Intra video
- 24-bit, 48 kHz PCM audio
- Some metadata describing the programme
- MXF OP1a wrapper
- A data rate of around 50 GB per hour
Nothing is ever that simple though, and there's actually quite a lot of complexity involved and scope for variation. Building on our earlier work towards writing the AS-11 specification and developing , over the past nine months we've been providing technical expertise to the DPP's . This programme is helping the industry to develop tools to read, write and manipulate AS-11 DPP HD files.
A matter of confidence
One good thing about videotape is that the format is very tightly controlled by the manufacturer because it is hardware based. This gives the broadcaster a high degree of confidence that they'll be able to play it back without any problems. An HDCAM SR tape recorded in one HDCAM SR deck will generally play back effortlessly in another HDCAM SR deck.
In contrast, with the format for AS-11 DPP HD files being an open standard, anyone can read the specification and write software to implement it. This is great for competition and enabling development of new and interesting products that use the format. However, it's a potential minefield for ensuring files from one device work with another – what we call interoperability.
There are no interpretations, only facts
We wanted to ensure people could have the same confidence when using files as they have with videotape. The DPP hosts "Interoperability Days", allowing manufacturers to swap files and see who can play what. It was clear from these events that people were interpreting the specification differently. To clear things up we created as a series of "rules". This not only gave the industry some much needed guidance, but also made sure we were absolutely certain that we knew what we were asking for.
Setting a benchmark for certification
The DPP and the AMWA wanted to certify products that meet testing criteria. To do that we needed to design a suite of tests that could be carried out as part of the DPP Compliance Programme.
There are tools available for testing files, so we started by looking at their capabilities. Understandably, there were some gaps in the coverage, so we also wrote some of our own analysis tools. To test if products could read AS-11 DPP HD files we created files that explore some of the known interoperability issues, and also gathered some from products that we were testing as File Writers.
However, it is products that are certified rather than files. We had to ensure that the files we asked equipment manufacturers to read or write were representative of real programme files, exercised the normal operational use of the equipment, and covered a broad range of the scope allowed by the AS-11 DPP file format specification.
What next?
Six products have received AMWA AS-11 DPP Certificates so far, and more are being tested. We're also working on extending the test criteria so that we can test products that do things other than read or write AS-11 DPP HD files.
There are limits to how thoroughly and completely anyone can test a product, and the real test will be seeing how things work in practice. There's no doubt however that our work in this area has driven manufacturers towards adhering more closely to standards and, as a result, making products that interoperate better. The success of AS-11 DPP has led to interest from outside the UK – work's now needed to see how AS-11 can be developed for use elsewhere.
File based delivery is a big change for the industry and broadcasters are adopting it at different rates. Our contribution to the standards involved should increase interoperability and smooth the transition.
Edit 7 Oct 2014: Thanks to Jim Downie for pointing out from the Βι¶ΉΤΌΕΔ Academy, designed to help the production industry make the move to file based delivery.