Why 500MB for an hour of digitized videotape is not enough
When archivists used to working with text-based formats like PDF/A are introduced to video preservation, the size of video files such as .mov or .mxf are often a shock. A 1-hour video file at 500MB seems huge compared to document files, but in the world of audiovisual preservation, but is not enough to serve as a proper archival master. Furthermore, management of file formats should be considered in the wider strategic context of preservation planning. What can your organisation afford to do? Learn more about the subject on this page.
Understanding the relationship between file size, compression and quality is key to making informed decisions about digital preservation.
How file size reflects Quality
The size of a digital file is determined by its resolution, bit depth, frame rate, compression and whether it keeps all the original data (lossless) or throws some away (lossy). Many archivists unfamiliar with AV materials assume because a document can be preserved in a compact format, the same applies to audio and video. But the nature of visual and auditory media means higher data rates are required to maintain integrity.
Typical file sizes for 1 hour of Archival content
Format / Codec |
File size for 1 (hour) |
Use case |
| PDF/A (text document) | ~ 10MB | Archival document standard |
| High-quality JPG (image) | ~ 10MB | Compressed photographic preservation |
| TIFF (uncompressed image) | ~ 100MB | High-quality image preservation |
| BWF (Broadcast WAV – uncompressed audio) | ~ 2GB | Archival audio standard |
| FFV1 (mathematically lossless compressed) | ~ 35GB | Preservation-quality standard definition (SD) video |
| V210 (uncompressed video) | ~ 100GB | Preservation-quality high-definition (SD) video |
| 4K DPX sequence (film scan) | ~ 2TB | Archival-grade film scan at 4K |
| H.264 MP4 (compressed SD video) | ~ 250MB to 1GB | Access copy, not suitable for preservation |
Lossy vs. Lossless: why it matters
Many preservation mistakes come from using highly compressed formats, such as MP4 (H.264) or .mp3, which dramatically reduce file sizes but permanently discard visual and audio information. While such formats are acceptable for access copies, they are not suitable for long-term preservation because data loss is irreversible.
For example:
- A one-hour mp4 (H.264) SD video file of 500MB lacks significant details and introduces compression artifacts
- The same content stored as FFV1 (lossless SD video) at 35GB retains every bit of visual and audio data.
Similarly, audio stored as mp3 at 128kbps will sound significantly degraded compared to a BWF (Broadcast WAV) at 24-bit/96kHz.
Film scanning: why a 4K DPX sequence can be 2TB per hour
Film, due to its analog nature, is best preserved at high resolutions. Scanning a 16mm film reel to 4K DPX can result in ~2 TB per hour, a staggering size for those used to working with digital documents. However, this resolution ensures the preservation of every grain, color variation, and frame detail.
Can everything be Lossless? A practical approach
While archive master copies should be preserved in lossless formats, not all historical content may require the highest quality. A documentary recorded off-air on VHS in the 1980s may not need a 10-bit v210 uncompressed video file, but the original magnetic master tape must be digitized with as much fidelity as possible before it degrades beyond recovery.
Decisions should be made based on:
- The historical value of the content
- The likelihood of future re-use and restoration
- Available storage capacity vs. expected longevity of the archive
- Performing tests to verify the best possible balance between quality and file size
One key rule: Always digitize at the highest reasonable quality first, as there will likely not be a second chance. Many legacy formats, especially magnetic tapes, are deteriorating, and playback equipment will be unavailable.
Final thoughts: the price of doing it right
A poorly quality file cannot be restored to its original carrier quality. Once lost, detail is gone forever. While storage concerns are valid, modern infrastructure allows for cost-effective archival solutions, especially for institutions preserving culturally significant works.
Archivists should approach audiovisual preservation with the same care as traditional documents, recognizing that file size is not an inconvenience, but a necessity for accuracy and authenticity. Digital archiving is an investment, ensuring that future generations can experience historical content as close to its original form as possible.
If there’s only one chance to do it right – do it well.
