In theory, more CRTC registers could be changed, for example, one could change the scanning region from 320x200 to 256x256. The Vidi software doesn't include any such features.
Note: Internally, the CRTC stores the scanline data in SRAM in the same "interleaved" format as it is also used in the CPC's VRAM(ie. line 0,8,16,24,etc.). However, this effect is "undone" when the CRTC reads the stored scanlines (so the CPU receives data without interleave. oe. line 0,1,3,4,etc.).
=== Scanning Modes ===
The software supports 3 modes (at hardware side, there are only 2 modes):
* Mode 2 - 640x200x1 - true hardware mode(0=black, 1=white)* Mode 1 - 320x200x4 - true hardware mode(0=black, 1=dark grey, 2=white, 3=light grey)
* Mode 0 - 160x192x16 - special software mode: the software performs sixteen Mode 2 scans (with different brightness settings in each pass), and combines them to a 16-color image. Obviously, this method works only with still images (camcorder aimed at still image, or VCR with "freeze picture" mode). Moreover, the CPC with [[CTM640/CTM644]] colour monitor can't display 16 grayscales so the picture will look like crap, however, it will look pretty much perfect on a [[GT64/GT65]] green monitor. The software scans only 192 lines in this mode (not 200 lines), but this is just due to lazy programming (the programmer didn't handle the region "under" the OSD menu at the bottom of the screen). In mode 0 scanning, the user/software selected brightness is ignored (because the whole sixteen I/O selectable brightness values are used for the sixteen passes), so, brightness can be adjusted only via the potentiometer.
For the two hardware modes, the bits in the capture bytes are having the same format as CPC VRAM (observe that in Mode 1, white is color 2, not color 3). For the software mode, obviously, the format depends on the software (the VIDI software uses CPC VRAM format, with color 0..15 = black..white).
=== Disassembly ===
Image:Rombo Vidi Mode0 Sample on GT65.png|Mode 0 on GT65
Image:Rombo Vidi Mode0 Sample on CTM644.png|Mode 0 on CTM644
Image:Rombo ebay.jpg|VIDI video digitizer as seen on Ebay 2010
</gallery>
Image:Vidi Publicity 1.jpg|Advert 1
Image:Vidi Publicity 2.jpg|Advert 2
Image:VIDI ad ACU March1987.jpg|Advert 3
</gallery>
* [[Media:Vidi Manual.txt|VIDI Manual]] (txt)
== Software Download ==
* [[Media:Rombo Video Digitiser.zip|Rombo Video Digitiser.zip]] (DSK for Emulators)
* [[Media:VIDIR202.ROM|Rombo Video Digitiser ROM]] (ROM for ROM expansions)
Software was available on cassette, disc, and (as an upgrade option) on ROM. The latter one requires an external ROM BOX to be of any use (the Vidi board doesn't include a ROM socket).
== See also ==
* [[ARA Video Digitizer]] - another video digitizer ([[Jagot & Leon]])
[[Category:HardwareGraphic]] [[Category:Peripherals]] [[Category:Manual]]