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Storage requirements for digital video
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Simple formulas can be used to calculate approximate storage requirements for digital video:
File size = bitrate * number of minutes * .0075.
Bitrate = file size / (number of minutes * .0075)
Number of minutes = file size / (bitrate * .0075)
For example, 2 hours (120 minutes) of video compressed using a 175 mb/sec codec will require approximately 157.5 GB of storage space.
157.5 GB = 175 mb/sec * 120 minutes * .0075
Digital videocassettes
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Digital "master" files and "access copies" produced by reformatting digital videocassettes through direct data transfer should be created according to the following technical specifications:
- Digital "master" file:
- MKV or MOV wrapper
- Native codec and native audio
- The original data should be captured in its entirety
- Maintain the original aspect ratio, recording standard, interlacing, number of audio channels and auxiliary information such as original timecode and closed captioning
- Digital "access copy":
- MPEG4 wrapper
- Video encoded using the H.264 codec
- Bitrate of 5000 Kbps
- Audio encoded as uncompressed AAC, 44.1kHz, 256 Kbps
- Maintain the original aspect ratio, recording standard, frame rate, number of audio channels and auxiliary information such as original timecode and closed captioning
Technical specifications for digital "master" files by source media type
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- Technical specifications should always be tested and adjusted if necessary before digitizing or transferring a new batch of moving images.
- Moving images acquired on optical disc (e.g., CD, DVD, Blu-Ray) are captured in the Digital Forensics Lab. See the Digital Forensics Lab manual for guidance on capturing data acquired on optical disc.
- Digital master files for digital videocassettes (e.g., DV, DVCAM, DVCPRO, Digital8) should be generated through direct data transfer whenever possible.
Media type | Format | Video bit depth | Codec | Audio data encoding | Audio bit depth | Audio sampling rate | Wrapper | Minimum file size for one hour of digital video |
16 mm film | Film | 10-bit | YUV 422 or FFV1 | PCM | 24-bit | 48 kHz | MXF or MOV | |
35 mm film | Film | 10-bit | YUV 422 or FFV1 | PCM | 24-bit | 48 kHz | MXF or MOV | |
| Umatic | Magnetic tape | 10-bit | YUV 422 or FFV1 | PCM | 24-bit | 48 kHz | MOV or MKV | |
Betacam | Magnetic tape | 10-bit | YUV 422 or FFV1 | PCM | 24-bit | 48 kHz | MOV or MKV | |
Digital videocassette (DV, DVCAM, DVCPRO, DVCPRO HD (720p) | Magnetic tape | 8-bit | Native codec | Native audio encoding | Native audio encoding | Native audio encoding | MOV or MKV | |
| DVCPRO HD 1080i and 1080p | Magnetic tape | 10-bit | Native codec | Native audio encoding | Native audio encoding | Native audio encoding | MOV or MKV | |
CD, DVD, Bluray | Optical disk | PCM | 16-bit | 44.1 kHz | ISO |
Digital videocassettes
Digital "master" files and "access copies" produced by reformatting digital videocassettes through direct data transfer should be created according to the following technical specifications:
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References
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Kong, David. "The Simple Formula to Calculate Video Bitrates." Frame.io Insider. Accessed January 14, 2021.