Looking for a suitable output format for digital video
The digital transfer of DV cassettes is central to digitisation project 7. It’s a digital transfer because we’re dealing with a digital signal, but in order to preserve the content on these carriers, the signal needs to be converted into a sustainable file format. There was no consensus yet about what the best file format for this was, so we went looking for the ideal output format for our content partners’ 22,000 DV cassettes.
At first glance, DV cassettes – DV, DVCAM and DVCPro – are not unusual carriers. They’re just tapes in plastic cases, which we see a lot of at meemoo. But converting their content is still a technically complex affair. One reason for this is the signal loss and the precision work that’s involved with adjusting the reading heads and maintaining the machines. But another thing that makes them special is the different ways the content is recorded using digital signals. Some examples of this? The ratio between the image’s height and width can be 4:3 or 16:9, images can be recorded using the European PAL or American NTSC standard, and recordings can be made in ‘long-play’ or ‘short-play’ mode.
And perhaps most remarkable of all: cassettes can even contain a mix of these characteristics. So every cassette can be different, and that’s the main challenge for their digital transfer: we can copy the image and sound as it is, but such great technical diversity is difficult to manage in the archive. If we convert the signal so that each video file has the same technical characteristics, there’s a very good chance you’ll notice this technical manipulation in the images and sounds, with the video file no longer looking the same as it does on the cassette, which is of course our intention. So what’s the best compromise? And how can a digitisation company achieve it in a way that’s also efficient and not unreasonably expensive?
In order to find out, trainee Gaël started by looking at possibilities for converting this media before being joined by Peter Bubestinger-Steindl, an Austrian specialist in digital video formats. We used this document as a basis for the specifications and to fine-tune the way we worked with the digitisation company Memnon.