Contents:
- Firstly, what are checksums for?
- Checksums within Audiovisual Data: DV Tape and DIF Block Parity Data – MPEG and CRC Checks – Lossless FLAC and MD5 Signatures
- Codec Independent Implementations of Frame Based Checksums
- Whole-File Checksum plus framemd5: Determining Extent and Relevance of Digital Change – Verifying Lossless Transcoding – Under Development
- in Summary
This paper, whose subtitle is “Detecting digital change in audiovisual data with decoders and checksums”, examines the relationship between audiovisual data and the objectives of checksums, reviews tactics to allow the effectiveness and function of checksums to scale for audiovisual content, and reviews the history of checksums in use within digital video to enable error detection and error concealment. Beginning with what role checksums play within digital preservation, the article goes on to illustrate the differences and value of whole file checksums vs per-frame checksums in audiovisual files, how embedded checksum functionality is built into audiovisual codecs such as dv, mpeg, flac and how this kind of granular checksum generation functionality could be implemented for other codecs using the framemd5 format. This article was initially published in the IASA Journal number 29, June 2012.
The author successfully argues why audiovisual digital preservation requires more than whole file checksum information and offers a variety of proposals to use existing or generate frame based checksum information. Although the article discusses a somewhat technical subject and includes command line utility functions as illustration, its explanations are generally clear enough for the non-technical archivist to understand. Useful article for those responsible for ensuring file integrity in the digital repository.