Preservation Formats - The EVIA Digital Archive Project

Preservation Formats

home research & development digital preservation of video

When the EVIA Project began in 2001, no standards or widely accepted best practices for digital video preservation existed. Much has improved in the way of industry practices, file formats, and digital technology capabilities, but no set of standards or best practices has been adopted by any national or international agency to date. This has created significant challenges, but the EVIA Project works to be as forward-looking as possible in anticipation of technological changes as well as long-term file migration issues.

While the preservation file format is just one piece of a preservation strategy, it is an important one. The format must be able to capture as much of the original signal as possible, be affordable, and be part of widely adopted and supported technologies. Compression and highly proprietary solutions must be avoided. The only viable file format available during the EVIA Project planning phase in 2001 was MPEG2, which was widely used and capable of accommodating a large range of quality levels. We chose a 50 mbps I-frame only MPEG2 file format, which ensured that all frames were preserved with a relatively low level of compression. MPEG2 was no more than an interim format, however, as the true preservation master for our analog sources was a Digital Betacam tape copy. Although it had the disadvantage of being a tape format, it had advantages of being widely used in the video production industry, using only mild video compression, and using no audio compression. While we knew that migration would need to occur within ten years, the Digital Betacam tapes provided us with an excellent preservation format.

Beginning in the fall of 2008, we moved to a new preservation transfer procedure. Advances in computing speed along with a decrease in storage costs enabled us to make uncompressed video preservation masters from analog sources. This eliminated our need to make Digital Betacam tape copies. While the uncompressed files are quite large—125 GB per hour of video—we feel confident about migrating them into the future. Our approach to MiniDV recordings remains unchanged. The DV codec uses a 5-to-1 compression scheme, but it is a digital format. We transfer the tape to a file by using the native codec of the recording and by putting the transfer in a QuickTime (.mov) wrapper.

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