5 Nov
2007
5 Nov
'07
11:55 p.m.
Eventually I'll be shipping various 8-bit machines to the US, and was thinking
of using a PC with a TV card as a display (most of the machines have UK PAL RF
outputs, and I could add modulators to the ones that don't).
However:
- All TV card software I've seen has been utter crap, when it even works
at all.
- Typically there seems to be no scaling of the picture to fill the PC
screen.
- There's an obvious quality drop in the RF stages.
- I'm warned that the digital tuners in TV cards often have problems
locking on to the weaker signal produced by home micros.
I am sure I've seen vido capture devices with USB interfaces on the
computer side and a composite or S-video input on the other side. Using
one of those would avoid the loss in quility from the modulator and any
problems with the TV tuner side of things, but wouldn't be as good as
takinmg th RGB signals drectly.
So... how about hooking straight to the TTL RGB outputs of the vintage
machines and somehow sampling lines of data into the PC for display in a
window (with appropriate scaling in software as/when necessary so that the
image more or less fills the PC display)?
Surely someone's homebrewed something like this already? I presume the speeds
at which things need to work can be pretty high - but in theory it's just an
Most _home_ computers (as opposed to workstations) have a dot clock under
16MHz. Not that high by modern stadnards.
RGB framegrabber but without all the analogue-type
circuitry needed to decode
a picture?
I'm planning on shipping a few TTL RGB displays to the US, but maintaining
them is going to be more difficult than maintaining the machines (and I
It shouldn't be that hard...
imagine there are all sorts of pitfalls in taking a
US-designed TTL RGB
display and trying to use it with a UK-designed micro, as the frequencies
involved won't be quite the same)
The horizontal frequencies are much the same on UK and US TVs (15625Hz
.vs. 15770Hz). I doubt there exists a monitor that can lock to one and
can't be tweaked to lock to the other. Modifying the vertical deflection
circuit is a lot easier in general, sinxe (1) it's a lot slower and (2)
it doesn't have other functions, like EHT generation, hung off it.
Having done the reverse many times (used US machines with UK monitors) I
doubt it'll be much of a prolem.
-tony