Seen on RISKS-L

There's more technical info at http://www.atsf.co.uk/dottext/domesday.html The videodisk players were specially modified for this purpose. "The data channel appears on a SCSI bus ... and SCSI had only just been standardised at this time. This means that the player looked to the host computer like a very large, somewhat slow, read-only hard disc. We had never used a CD-ROM at that point. A read-only version of the BBC Micro hierarchical disc filing system, now called VFS (for Videodisc Filing System), is used to access the data in a way that adhered to the filing system standards. In this way any code written for one filing system could be used with another, providing both use the same subset of the whole standard. Write-only systems obviously do not have sector write primitives or means of modifying file attributes for example." It sounds like images were stored as PAL frames and were converted to RGB for mixing with the BBC RGB output.