Deinterlacer
~~~~~~~~~~~~
See also, Deinterlacer-Tuning

The Amiga traditionally operates in a native NTSC or PAL mode video
system.  All of its normal output runs at 15 KHz, 50 or 60 Hz refresh.  In
high resolution modes such as NTSC:HiresInterlaced, the output is
interlaced, which means more information is presented by quickly swapping
"fields" of video data on the monitor.  This generates a horrible flicker,
which some Amiga users have grown accustomed to, but others find
disturbing.

While many solutions were presented by the early Amiga community,
such as wearing sunglasses and putting dark glare shields on their
monitors, Commodore came up with an ingenious device, named the Display
Enhancer, or FlickerFixer.  (Actually, another company, MicroWay, made a
similar product, trademarked FlickerFixer, but....)  This is implemented
into every Amiga 3000 system, and can be also purchased separately for
A2000/4000 systems in the A2320 board.

The Display Enhancer is a scandoubler / deinterlacer system.  It
takes the 15 Khz output, and converts it into 31 Khz signals suitable for
flicker free video.  If it's noninterlaced, it doubles the signal, removing
visible scanlines.  If it's interlaced, it deinterlaces it, removing
flicker.  If it's not 15 Khz, it just passes the signal through.  The
entire system can be defeated by a toggle switch on the back.

While the system works remarkably well, there are a few problems.
For one, it will only affect NTSC: (or PAL:) signals.  And some video modes
like NTSC:SuperHiresInterlaced don't quite work properly due to hardware
constraints.  But all in all, it means A3000 owners can get VGA quality
displays without running their systems in odd screen modes.


Technical Information
~~~~~~~~~~~~~~~~~~~~~
As far as I know, the Amber deinterlacer circuitry samples in the
15KHz signal from the motherboard, and converts it to 31 KHz.  There is a
fast dual port video memory segment in the system that accomplishes the
simultaneous sampling and output.