Marriott Library Blog

That’s right. You heard me. Lossless video compression is pretty cool. It actually has a coolness factor of about 4.3 out of 5. That’s a lot when you think about it. In fact, TV’s “The Fonz” only has a coolness factor of 4.1, if that puts it into perspective for you.

But why is lossless video compression something we should care about, regardless of how cool it is? As part of my position as Digital Preservation Archivist at the Marriott Library, I’m tasked with creating a sustainable digital preservation program for the library’s unique digital collections and as part of that process, I’m making sure we also conserve server space. Uncompressed audio/video files take up a great deal more space than uncompressed text and photo files and that’s where lossless compression comes in. Lossless video compression refers to the fact that

the output from the decompressor is bit-for-bit identical with the original input to the compressor. The decompressed video stream should be completely identical to the original. – Ian Gilmour, R. Justin Davila

So, unlike lossy compression, lossless compression enables the need to store only the moving parts in any given image, without losing image quality when the original file is uncompressed. If, for instance a scene consists of The Fonz hanging out by his parked motorcycle, chatting up one of the waitresses at Al’s Diner, the compression scheme would be concerned with the objects that are moving within the frame (i.e. The Fonz, the waitress, the birds in the sky). The motorcycle and the diner aren’t changing at all, so there’s no need to store multiple copies of those images. When this scheme is kept internal to the image frame, this is referred to as intra-frame compression which is able to save large amounts of data when compared to the uncompressed file, which would store every pixel in the original image.

Inter-frame compression includes data from across the entire shot or scene. Entire sequences of frames with similarities can be encoded, with only the differences in the frames being specified. This means that the information not changing throughout the entire scene (rather than one frame as in the case of intra-frame compression) of The Fonz and the waitress can be compressed and later decompressed with no loss in image quality. Inter-frame is interesting because under certain conditions (typically when using lower bit-rates) the differences throughout a scene (known as temporal or inter-frame encoding techniques) require less data for picture quality than encoding every frame does.

Inter-frame encoding typically maps groups of pixels within macroblocks which stay the same from one frame to the next [i.e. fixed backgrounds] or which move in the same direction [e.g. moving objects or panned backgrounds]. Rather than encoding these image regions, their relative positions are tracked using motion vectors, which require much less coding.
- Ian Gilmour, R. Justin Davila

For a much more detailed look at lossless video compression, take a look at the piece referred to above by Ian Gilmour of the Australian National Film and Sound Archive and R. Justin Davila of Media Matters, LLC., Lossless Video Compression for Archives: Motion JPEG2 and Other Options.

And stay tuned to this blog for more on various recommended lossless audio and video compression codecs.

The Marriott Library’s digital collections page is a gateway to various formats  of digital content including text, sound and video (to name a few).  The Marriott Library is diligently working to expand its digital audio collections such as the Western Soundscape Archive and the Doris Duke Oral Histories.  The Digital Technologies department is presently trying to perfect certain facets of the audio format workflow such as file compression, format selection, long term preservation and accurate representation of the compressed files.  The recent focus on audio makes WSA (Western Soundscape Archive) a well deserved candidate for this week’s show and tell.

The Western Soundscape Archive collection has benefited from much deserved attention in the form of press releases and podcasts, and is now also being aired as a weekly radio series on KUER.   This is a unique and searchable online collection featuring audio recordings of species and of their natural environment in the western United States.  The source audio files are recorded by a team of recording engineers and are handed off to the Marriott Library where they are compressed and streamed as MP4.  In September of 2007, the WSA collection was a recipient of a three year National Leadership Grant from the Institute of Museum and Library Services (IMLS), and it has accomplished much since then.  The collection varies anywhere from sound recordings of species in their natural habitat, to ambient recordings of soundscapes, and spectrograms  (visual representations) of acoustic observations of the Natural Sounds Program, conducted by the National Parks Services. 

If you care for a wonderful alternative to sitting down and replying to a work email, or sweating over the deadline for that dreaded report, then look no further; follow a crew of biologists trekking through the grounds of the Beaufort Lagoon of the Arctic National Wildlife Refuge and listen to the whimsical call of an arctic fox (because I know that is something you have always wanted to do!):   

http://tiny.cc/arcticfox

You can also follow Jeff Rice (co-Principle Investigator for Western Soundscape Archive) to the beautiful Red Butte Gardens of Salt Lake City while he records the rattlings of a Great Basin rattle snake :

http://tiny.cc/rattlesnake

Or better yet, check out the Burrowing Owls of Snake River, Idaho while they mimic rattle snakes!:

http://tiny.cc/owls332