I can't see how a lossy format like MP3 is even considered "archival." It should be discouraged as a preservation file format. I'm not sure lossless compressed formats are a good idea either, given the likelihood of more valuable content packed per disc drive, location, workstation, etc and simple probability thus making the data more vulnerable. Storage is cheap. Overlapping redundent storage is what I'd consider Digital Archiving 101, and included in that would be avoiding source-degrading things like lossy file formats. What I recommend to all my clients is, do the transfers high-resolution. Do your processing high-resolution. If you choose to save a final processed copy in lower resolution or lossy format, that's fine but keep the original transfer, it's worth a few hundred extra dollars per year in hard drives.
Here is what I wrote about DSS (the Olympus format) and others in August 2006 http://richardhess.com/notes/2006/08/17/dss-and-other-compressed-digital-files-in-an-oral-history-archive/
-- Tom Fine
----- Original Message ----- From: "Mike Richter" <mrichter@xxxxxxx> To: <ARSCLIST@xxxxxxxxxxxxxxxx> Sent: Sunday, April 06, 2008 4:55 PM Subject: Re: [ARSCLIST] Digital Audio Preservation Question
Martha Horan wrote:Hi,
I'm a library school student working on a digital repository project for a course on digital preservation. My group and I have audio files from a nearby archive that we plan to ingest into the D-Space repository. A large portion of the files that we received are in the lossy Ogg Vorbis and MP3 formats. The archive received the material from the donor in this way. Finding the right way to preserve the mainly born digital materials has been a challenge.
We are trying to figure out the best practice for this situation. Do we want to preserve how the files came to us and only put Ogg Vorbis or MP3 files in the repository, making those files the Preservation Masters?
Or do we want Wav files as well, to have a lossless copy of the files? Then we would have a combination of both the original and lossless files as the Preservation Masters.
It is my understanding, however, that it is bad practice to have a file compression that goes from lossy to lossless. Would the Wav file then not be considered preservation?
Or if we input enough preservation metadata to record the compression change that happened to the file, is the Wav (and the lossy to lossless compression) acceptable as a Preservation Master, accompanied by the original lossy file format?
The losses of a lossy format cannot be recovered. Decompressing to WAV will preserve the sound as you received it, but so will a copy of the original file. The only reason to decompress would be for editing. If you intend to process the files in any way, the edited result should be saved in a lossless format so that the losses are not compounded.
Mike -- mrichter@xxxxxxx http://www.mrichter.com/