File ID Hackathon Debrief: FITS Handles Video Now!
I took part in the 24-hour file ID hackathon November 16th. It was a fantastic event, and between us the 15-ish participants got a lot of practical work done. You can read more about it and what was accomplished at the CURATEcamp wiki.
I spent most of my time working with video content and with FITS, the File Identification Tool Set. FITS is a useful tool, but it’s traditionally had some problems that have held it back from being as effective as it could for digital preservation. Aside from its performance, which is an issue that still needs to be addressed, its support for audio-visual material has been pretty poor. I addressed a couple of the more serious items:
Its embedded Exiftool was badly out of date
FITS bundles its own versions of the various tools it uses, rather than use the versions installed elsewhere on the machine. In theory this is a good idea; incompatibilities in the tools it uses could subtly break its output. In practice, however, it means that FITS has missed out on a lot of format identification improvements its tools have made. Before the hackathon FITS included exiftool 7.74, which was released in April, 2009. Back then exiftool had only rudimentary video support, but it’s made enormous strides in past several years and now has very robust video metadata extraction. The first thing I did in FITS was update the embedded exiftool to the current release. That alone has made a big difference in format detection.
In the future I think it would be best to rethink the policy of embedding tools rather than using external copies, or at least provide the option to use another version the user has installed. exiftool is updated once every week or two and changes rapidly. I doubt FITS will be updated that frequently. A better option might be to recommend specific known-good versions of tools, but allow the user the option of running whichever tool version they prefer.
Its metadata mapping for video formats was primitive
FITS uses XSLT to map metadata fields from their native tag names to its own vocabulary, but the list of tags used for video was very short compared to other formats. As a result, a lot of potentially useful information from exiftool’s output was being discarded. Based on videos in my collection which had extensive embedded metadata, I beefed up FITS’s mapping table to enable it to grab many more common tags.
While this made a good short-term solution, it made me think a bit more about how FITS approaches mapping fields. In particular,
FITS has separate mappings for types such as “image”, “video”, “audio.” In practice, though, many of these formats use the exact same tags to mean the same things; this means either some mapping logic is duplicated, or certain fields are skipped for some files even though they’re mapped for others. After looking at practical examples of how FITS maps images and videos, I’m not convinced that treating them separately is practical.
Beyond that, FITS uses file extension to determine whether a file is an image, video, etc. In practice many container file extensions can represent many kinds of files; extension is a pretty fragile way of determining type. If FITS keeps a distinction between file type mappings, it should move to using something like mimetype instead of extension.
Aside from my work improving FITS, I also submitted a set of Quicktime videos to the OpenPlanets Format Corpus on GitHub. The 61-video set covers almost every codec Apple ships with Quicktime and Final Cut Pro, and should be useful for anyone who wants to try to identify individual codec/container combinations. They’re available at: https://github.com/openplanets/format-corpus/tree/master/video/Quicktime
I’ll end this off with some eye candy, to show how nicely FITS’s video support has improved.
Before. The video is detected only as “Unknown Binary” (this was sadly common for video), and no meaningful metadata is extracted.