A video digitizer made by Philippe Borg in 1987, for a the french company called [[Jagot & Leon]]. The french name of the hardware is ''Digizaliseur Ara'' (seen on sticker), or ''Ara Digitaliseur d'images video'' (seen on screenshot).
ARA is said to be simply referring to the colourful parrot with same name (rather than being an abbreviation for something like analog recording apparatus or so).
The hardware consists of an A/D converter, and bunch of logic chips. It does also includes two 8K SRAM chips, used as 16K capture buffer (the image is captured to that buffer in realtime, and can then be read by software at slower speed).
The device connects to SCART connector on TV Set (or Video Recorder (or camcorder or other picture source). There seem to be no attempts to decode SECAM color informations, ie. only luminance (brightness) seems to be supported. Luminance should be same in all countries, so it should also work with PAL/NTSC.
Two capture formats are supported: 320x200x4 and 160x200x16. Of which, in practice, the software supports only max 8 colors, not 16 colors (nethertheless, the actual hardware might, or might not support 16 colors, and it's just the software ignoring their LSBs; the CPC's 27-color palette isn't suitable for displaying 16 "grayscales").
The captured data bytes are having the bits arranged differently as CPC's VRAM. For details, see the mode 0 and mode 1 translation tables in the disassembly.
=== I/O Port Summary ===
=== 10bit Config Value ===
The Z80's 8bit databus doesn't allow to write 10bit values. The ARA is using a rather strange solution to overcome that problem. The mechanism to set Config=N is:
OUT [F9F5h],garbage, FOR I=1 to N, OUT [FAF5h],garbage, NEXT I
Whereas, the separate bits in "N" are:
0-1 Contrast
2-5 Brightness
=== Dotclock ===
The dotclock (horizontal resolution) is unknown. For a CPC-like aspect ratio, it ''should'' be 4MHz (for 320 pixel resolution), which could be obtained from expansion port. However, the digitizer includes it's own crystal (the photo isn't clear there, it ''looks'' like 5MHz or 6MHz) (but more probably it's something like 16MHz, the leading "1" being invisible on the photo, 16MHz would be reasonable for splitting a 4MHz dotclock into 4 steps).
=== Disassembly ===
* [[Media:Ara video digitizer disassembled.txt]] - disassembled ARA.BIN scanning function
== Pictures ==
Caution: The software includes some french-cuisine-slang expressions which may confuse english users. For example, "ENTREE : DIGITIZE" means "begin with pressing D for digitize". Namely, it does NOT mean "to press ENTER for digitize".
== See also ==
* [[VIDI digitizer]] - another video digitizer (Rombo Productions)
[[Category:Peripherals]][[Category:Graphic]]