Capture Specifications
Included below are the digital file formats and ancillary specifications for the encoding (digitization or transcoding) of audio and moving image content we typically use at the MSU Libraries. First, here are our file format profiles:
A Preservation File, in this context, is the highest quality digital file, meant to be maintained in perpetuity and for creating copies of the original (not for transcoding access files). Whether it is transferred from an analog or digital source, each one of the preservation profiles outlined below are intended to maintain the fidelity of the original while also avoiding secondary digital obsolescence.
A Mezzanine File is a mid-level surrogate for the preservation file: robust yet computationally manageable (i.e. compressed). This is the file accessed for transcoding, editing, or in cases where close review is necessary. Also referred to as a "production-quality" file.
Access Files are available to researchers on-site or for streaming/download via the local network. Levels of access will depend on the rights and permissions MSU Libraries has to distribute the content.
Audio
| Preservation File, Analog Source | Preservation File, Digital Source | Mezzanine File | Access File | |
|---|---|---|---|---|
| Format |
Broadcast Wave Format (BWF; .wav) |
Broadcast Wave Format (BWF; .wav) |
Broadcast Wave Format (BWF; .wav) |
MP3 (MPEG-2 Audio Layer III) |
| Encoding | Uncompressed Linear Pulse Code Modulated Audio (LPCM) | Uncompressed Linear Pulse Code Modulated Audio (LPCM) | Uncompressed Linear Pulse Code Modulated Audio (LPCM) | MP3enc, Lame |
| Sampling rate | 96 kHz or 44.1 kHz (if spoken word) | Native (e.g. 44.1 or 48 kHz) | 44.1 kHz | 44.1 kHz |
| Bit depth | 24-bit or 16-bit (if spoken word) | Native (e.g. 16-bit) | 16-bit | N/A, not LPCM. Bitrate = 160 Kbps (mono) or 320 Kbps (stereo) |
Audio Sources
- International Association of Sound and Audiovisual Archives Technical Committee. (2009). Guidelines on the production and preservation of digital audio objects (IASA-TC04, 2nd ed.). Retrieved May 19, 2015, from http://www.iasa-web.org/tc04/audio-preservation: Opens in a New Tab
- Casey, M., & Gordon, B. (2007). Sound directions: Best practices for audio preservation. Trustees of Indiana University and President and Fellows of Harvard University. Retrieved May 19, 2015, from http://www.dlib.indiana.edu/projects/sounddirections/papersPresent/sd_bp_07.pdf : Opens in a New Tab
Video
| Preservation File, Analog Source (NTSC) | Preservation File, Digital Source | Mezzanine File | Access File | |
|---|---|---|---|---|
| Container/Format |
Matroska (.mkv) |
Matroska (.mkv) |
QuickTime (.mov) |
QuickTime (.mov) or H.264/MPEG-4 AVC (.mp4) |
| Encoding | FFV1 | Native (e.g. DV; H.264; IMX) |
DV50 |
H.264 |
| Bit depth | 10-bit | Native (e.g. 8-bit) | 8-bit | 8-bit |
| Color space | YUV | Native, presumably YUV | YUV | YUV |
| Chroma subsampling | 4:2:2 | Native (e.g. 4:2:2; 4:1:1; 4:2:0) | 4:2:2 | 4:2:0 |
| Frame size | 720x486 | Native (e.g. 720x480 [SD]; 1440x1080 [HDV]) | 720x480 | Variable (e.g. 640x480; 1280x720) |
| Frame rate | 29.97 fps | Native (e.g. 29.97 fps) | 29.97 fps | Inherited from source |
| Video bitrate | 25–27 MB/sec (200–216 Mbps) constant | Native (e.g. 25 Mbps; 50 Mbps) | 50 Mbps (~7 MB/sec) | 0.6–1.7 Mbps (600–1800 Kbps) |
| Audio stream | 48 kHz / 24-bit PCM | Native, typically ≤ 48 kHz / ≤ 24-bit PCM | 48 kHz / 16-bit PCM | AAC; Stereo / 48 kHz / 192 Kbps |
Preservation File from an Analog Source: Playback into encoder, wrap output data stream(s) as file.
Preservation File from a Digital Source: Transfer data stream(s) to file container without transcoding. If optical disc, extract ISO image (.img; .iso) of disc to capture all components. Typically the DVD video object (.VOB) files are also extracted and repackaged into a Matroska container (.mkv).
Video Sources
- Federal Agencies Digitization Guidelines Initiative Audio-Visual Working Group. (2014). Creating and archiving born digital video. Retrieved May 19, 2015, from http://www.digitizationguidelines.gov/guidelines/video_bornDigital.html: Opens in a New Tab
- Federal Agencies Digitization Guidelines Initiative Audio-Visual Working Group. (2014). Digital file formats for videotape reformatting. Retrieved May 19, 2015, from http://www.digitizationguidelines.gov/guidelines/video_reformatting_compare.html