The preservation of digital video is complicated and handled in a variety of ways at the Smithsonian Institution Archives (SIA). Unlike a text document or a jpeg, digital video is wrapped with the audio in a container or wrapper, such as Quicktime MOV or Microsoft AVI. This container might also have metadata and subtitles. A codec (encoder/decoder) is what processes the video and audio and allows the decoding for playback. A codec can be lossy compression (smaller size but data loss through discard of redundant information that can’t be retrieved) or lossless compression (no data loss but larger files).
In preserving digital video, if it arrives on media like a DVD or thumb drive, a transfer of files is completed as soon as possible to the server and the media is retained. Digital video from a network share or cloud service is transferred directly to the Archives’ server, and a copy is also created.
Current Archives’ practice is to ensure that digital files can play back correctly on workstations. The Archives has implemented a preservation workflow for authored DVDs that contain VOB (wrapper) files. ISO disk images are made to create a container of the DVD contents. The Archives uses ISO because it allows playback of the video with its menus when mounted on a computer but does not require that original DVD. In some instances, MP4 files are created for access from the DVD files (see the blog posts below for more information). Some of the Archives’ collection programming that once was on authored DVDs now are being delivered as direct file transfers as MOV files, which makes for easier management and processing.
In other cases, no additional actions are taken to convert to other wrappers or codecs of the digital video. While there is usually general agreement in the digital preservation community about acceptable formats for long-term preservation of other types of digital records (e.g., word-processing converted to PDF/A or TIFF for images) there is no “one-size-fits-all” when it comes to digital video due to its complexity and the needs and capability of an archive or repository.
There are some steps though that content creators shooting video can consider to ensure better accessibility and preservation in the long term.
- Create uncompressed video if possible. This does create large files but they retain their quality. Storage also needs to be considered with this approach however.
- If uncompressed video is not possible, use lossless instead of lossy compression. The compressed data gets restored while lossy compression alters data and quality is lost.
- Use higher bit rates (affects resolution of image and size of file.)
- Use technical and descriptive metadata.
- Use containers and codecs that are stable and widely used within the community.
Related Blog Posts
- Digital Video Preservation: Identifying Containers and Codecs, The Bigger Picture, Smithsonian Institution Archives
- Digital Video Preservation: Further Challenges for Preserving Digital Video and Beyond, The Bigger Picture, Smithsonian Institution Archives
- Workflow Dynamics of Digital Preservation, The Bigger Picture, Smithsonian Institution Archives
- And Action: The Ins and Outs of DVD Video Preservation, The Bigger Picture, Smithsonian Institution Archives
- What are You Watching?, The Bigger Picture, Smithsonian Institution Archives
- Digital Video Preservation: Continuing the Conversation, The Bigger Picture, Smithsonian Institution Archives
- Born Digital Video Preservation: A Final Report, Smithsonian Institution Archives
- Creating and Archiving Born Digital Video, Federal Agencies Digitization Guidelines Initiatives