Bit | Meaning when set |
---|---|
0 | Non-graphics mode |
1 | Teletext mode |
2 | Gap mode |
3 | BBC gap mode (Modes 3 & 6) |
4 | Hi-res mono mode |
5 | Double height VDU chars |
6 | Hardware scroll disabled |
7 | Full 256 entry palette (only valid if Log2BPP == 3) |
65536 colour RGB 5:6:5 mode (only valid if Log2BPP == 4) | |
8 | Interlaced mode, with hardware using two separate framebuffers. |
9 | Greyscale palette, gradient from black to white (only valid in palletised modes) |
Indicates chroma sub-sampling mode (if Log2BPP == 7) | |
10-11 | Reserved |
12-15 | Data format and colour space information |
Bits 12 and 13 specify the basic data format/colour space. Bits 14 and 15 then give further details, to describe a number of sub-formats.
Data format | Sub format | Meaning |
---|---|---|
(bits 12-13) | (bits 14-15) | |
00: RGB | bit 14 | RGB order (0=VIDC style &BGR, 1=&RGB) |
bit 15 | Alpha mode (0=transparency/supremacy, 1=alpha) | |
01: Misc | 00 | CMYK |
Other | Reserved | |
10: YCbCr | bit 14 | range (0=full, 1=video) |
bit 15 | standard (0=ITU-R BT.601, 1=ITU-R BT.709) | |
11: Reserved |
OS_ReadModeVariable can be used to read the mode flags for the current screen mode, or for a given screen mode.