Three formats
Masters are kept in one of three formats. Broadcast WAV at 96 kHz and 24 bits is the default for everything recorded before the second winter. Thirty-two-bit float is used for eight-channel and binaural sessions, where the extra headroom avoids clipping in the lowest channel. A 48 kHz Broadcast WAV is used for rope, rain and other material with no content above 20 kHz, to keep sizes down. Working copies are made as FLAC at the same bit depth and sample rate.
Storage per hour
| Format | Channels | Per hour |
|---|---|---|
| Broadcast WAV, 96 kHz, 24-bit | Stereo | About 2.1 GB |
| Broadcast WAV, 96 kHz, 24-bit | Eight | About 8.3 GB |
| Broadcast WAV, 48 kHz, 24-bit | Stereo | About 1.0 GB |
| 32-bit float, 96 kHz | Eight | About 11.1 GB |
| FLAC, 96 kHz, 24-bit (working copy) | Stereo | About 1.1 GB |
These are uncompressed figures for the master format. Full sessions are often longer than the sum of their files, because each file also carries a short overlap at the join.
Choosing a format
- Use the eight-channel masters when the scene needs placement or a moving source.
- Each channel is labelled in the log header by position on the array.
- Mono downmixes are not supplied; they are left to the editor.
- Use stereo masters for layers, beds and single-location scenes.
- Stereo files are about a quarter of the size of eight-channel files for the same length.
- Use the float masters only where a level change in the source is expected to be large.