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Preservation and streaming file formats
The Stanford Media Preservation Lab produces audio and moving image files suited to purpose. This page outlines the encoding specifications we follow.
Audio
A preservation file is created to serve as the highest-quality archival file to be maintained in perpetuity for creating reproductions of the original recording. For digital sources, like DAT, the goal is to match the original resolution and encoding specs as closely as possible, if not exactly, in the file. The production-quality access file is a high-quality version of the archival file, and is useful for transcoding to a variety of user-friendly formats and media, such as Audio CD. The online access file is optimized for delivery via streaming or download. Other options, depending on the end-use context or delivery system, are possible.
| File type | Format | Bit depth | Sampling rate | Bitrate |
| Preservation file - analog source |
Broadcast WAV | 24-bit | 96 kHz |
2304 kbps (mono) or 4608 kbps (stereo) |
| Preservation file - digital source |
Broadcast WAV | At original resolution (typically 16-bit) |
At original resolution (typically 44.1 or 48 kHz) |
1411.2 kbps or 1536 kbps |
| Production-quality access file | Broadcast WAV | 16-bit | 44.1 kHz |
705.6 kbps (mono) or 1411.2 kbps (stereo) |
| Online access file | M4A | N/A | 44.1 kHz | 160 kbps (mono) or 320 kbps (stereo) |
Video
A preservation file is created to serve as the highest-quality archival file to be maintained in perpetuity for creating reproductions of the original recording. For digital sources, like DV, the goal is to match the original resolution and encoding specs as closely as possible, if not exactly, in the preservation file. The production-quality access file is a high-quality version of the preservation file and is useful for transcoding or for access in cases where detailed or close review is necessary. Online access files are available to researchers in reading rooms and listening rooms at Stanford.
Typical outputs are listed below. Other options, depending on the end-use context or delivery system, are available.
| File type | Format/wrapper | Bit depth | Color sub-sampling | Frame size | Frame rate | Video bitrate | Audio |
| Preservation file - analog source |
FFV1 (v3) / Matroska | 10-bit | 4:2:2 |
720x486 (NTSC) or 720x576 (PAL) |
same as source | ~110 Mbps (variable based on content) | PCM; 48 kHz/24-bit |
| Preservation file - digital source |
Raw DV stream (.dv) | 8-bit | 4:1:1 (NTSC) / 4:2:0 (PAL) | 720x480 (DV-NTSC) or 720x576 (PAL) 1440x1080 (HDV) |
same as source | ~25 Mbps | PCM; as low as 12-bit/32 kHz and as high as 20-bit/48 kHz |
| Streaming file | H264/MP4 | 8-bit | 4:2:0 | 640x480 (SD) or 1280x720 (HD) | same as source | 1100 kbps (SD) or 2800 kbps (HD) | AAC; stereo; 128 or 192 kbps; 48 kHz |
Film
Stanford's approach to film reformatting is evolving. While we have done some film-to-film transfers in the past, digital capture of film originals as video is now preferable given available resources and user requirements.
The table below outlines film reformatting specifications followed as of 2022.
| File type | Wrapper | Bit depth | Color Model | Frame size | Audio |
| Preservation file - 8mm source |
dpx | 10, 12, or 16-bit | RGB Log or Linear |
2048x1556 or 3840x2160 |
PCM, 24-bit/48 kHz |
| Preservation file - 16mm or 35mm source |
dpx | 10 or 16-bit | RGB Log or Linear |
2048x1556 or 4096x3112 |
PCM, 24-bit/48 kHz |