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).
=== Main Menu ===
To get here, press "E" in Boot menu (or ENTER at Slideshow Prompt). Available options are then... well, they are strange: The french cuisine related words, ''entree, hor's d'oeuvres, specialies specialites du chef, and dessert'' are jokes - ignore them. The actual options are:
D = Digitize
P = Paint (allows to edit colour scheme)
=== Digitize Menu ===
To get here, Press Type RUN"ARA, then press "E" , then press "D" after loading. Digitize mode doesn't discplay display any OSD menues or OSD help, so it's hard to use without manual (or without disassembling the code). Available options are: COPY = Apply current image (for later saving to disc) ENTER = Back to Main Menu (the COPY'ied image can be SAVED from there) ^ = Autoscan on (displays incoming data "animated" picture stream) SPACE = Autoscan off (useful only if you have a second screen, eg. TV set) U = Undo last capture (when U pressed twice: restore last capture) @ = Toggle video mode (320x200x4, or 160x200x16) UP/DN = Vertical picture position (+/- 1 step) (fine adjust) LT/RT = Vertical picture position (+/- 3 steps) (coarse adjust) ___Below are rows of keys on the keyboard:___
123456789 = Brightness (1=lower, 9=higher)
SDFGHJKL = Dithering (S=lower=no dithering, L=higher)
ERTY = Contrast (E=lower,Y=higher)
== Technical ==
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 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 ===
F8F5h - R - read sync signal (bit0)
F9F5h - W - reset 10bit config value to zero(write once to set config=0)
FAF5h - W - increment 10bit config value (write N times to set config=N)
FAF5h - R - read capture data (after capture was invoked and completed)
FBF5h - W - invoke capture
The three write-able ports are using a "write-strobe" mechanism (according to the disassembled software, the data written to the ports is don't care).
=== 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
6 Mode (0=320x200x4, 1=160x200x16)
7-9 Dither
=== 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 ==
* [[Media:ARA Digitaliseur Video Disc.zip]] (dsk)
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]]