Hello, and welcome to another episode of the 8-Bit Guy.
Today I'm going to talk a little about video digitizers.
This is an example of a video digitizer that most people will probably recognize.
It plugs into the USB port of your PC on one side, and you can connect a composite video
source to the other.
This will allow you to record video information from analog sources such as VCRs, security
cameras, or even old computers.
In fact, I use this one quite often when I'm showing screenshots of an old computer on
my channel.
These devices are largely unnecessary today because most of the video we capture these
days is already digital at the source of the recording.
And the whole point of a digitizer is to to make something digital that wasn't before,
in this case analog video to digital video.
What you might find interesting is that digitizers for personal computers actually go way back.
This example is from the early 1980s.
Computer Eyes was designed to plug into your Commodore 64, although I believe they also
made versions for other computers as well.
But the way in which this works may surprise you.
First of all, it doesn't do color.
It only captures in black and white.
OK, so that's pretty easy to explain.
But the next part is harder to explain.
This is what is considered a slow-scan digitizer.
You see, these modern digitizers are actually fast enough that they can grab entire frames
of video in realtime as they are being played, and convert them over to digital information.
These older ones aren't fast enough to do that.
Of course speed is only part of the problem.
Because, in order to buffer an entire frame of video, you would need a lot memory chips,
which this was at a time when memory chips were extremely expensive.
So that would have made a device like this prohibitively expensive.
So, what this device does is capture one single vertical line of video information each time
a frame comes through.
So it can take several seconds to grab an entire frame.
So let's talk about what it can and what it can't do.
So you might think you could use a VCR and grab pictures from that.
Well let's examine that.
I've got Back to the Future playing.
The first thing you have to do is press A for adjust sync.
If you look down at the bottom of the screen you'll see an indicator saying which direction
to rotate the sync knob.
So, I can movie it back and forth until it says it is in sync.
And no, I'm not talking about these guys.
Anyway, the next thing to do is adjust the brightness control.
So I'll press B here and it will display this sort of weird image on the screen.
I can adjust the control and immediately see changes as the image redraws on the screen.
But if you are thinking the image doesn't make any sense, you're not alone.
Since the image from the tape is constantly changing, the capture device can't get a
single frame digitized properly.
You might think you could just pause the tape.
But have you seen what VHS looks like when you pause it?
I tried getting a capture from this, but it wouldn't even sync up.
So you might be asking what good is it, if it can't capture even capture from something
as common as a VHS tape?
Well, if you had a really fancy VCR with a 4-head and better pause you might have had
some success, but if you had a laserdisc player, these things could do perfect freeze frames.
You could have definitely used it to capture images from that.
But, I think the most common thing to use would have been something like this old black
and white security camera.
These were common even back in the 1980s.
You could have also used a camcorder.
So this is what the image looks like from the black and white camera when captured onto
my modern computer.
But it's too hard to use myself as a subject to photograph here, so I'll point the camera
at this little rover.
I've found that high contrast objects work the best.
So this is what the security camera itself is seeing, I need to adjust the exposure….
and then the focus.
So as you can see, the image is now perfectly still.
So we should be able to capture something from this.
So I'll plug the camera into the capture device now.
OK, so I have the software running and I'll readjust the sync.
Now I'll do a brightness test.
Kind of a weird pattern, but you can sort of see the rover.
Next, I'll press N for a normal capture.
This takes about 7 seconds and only captures a 1-bit black and white image.
And there it is.
Well, that doesn't look so great, but at least you can make out what it is.
OK, so lets go back and try the 4-level capture.
This actually takes 29 seconds to capture, but I won't make you wait that long, so
here is the image.
OK, so that looks a little better.
I turned the brightness down and took the image several more times until I ended up
with this one.
Now with this you can actually see some detail.
So, knowing how this thing scans a photo, I thought it would be interesting to move
the camera up and down like this while it is doing the scan.
So with the normal mode, this is how it came out, which makes perfect sense from what we
know about how it works.
But I went back and did the same thing using the 4-level mode and came up with this.
This is not at all what I was expecting.
It appears to scan the image 4 seperate times.
So here are some other sample photos I took of various objects around the house.
But what about humans?
I managed to get my daughter to pose for a photo.
Keep in mind she has to stand still for 30 seconds while this was taken.
And here's how it came out.
I also got my wife to try staying still for 30 seconds, and then it was my turn to try
it.
This gave me a taste of what it was like to pose for photos back in the early days of
photography when exposure times were really long and nobody dared smile.
So, if you happened to own one of these back in 1984, you would have been like a computer
God.
And all of the other computer nerds in your circle would definitely want to be your best
pal so that they could occasionally borrow your digitizer.
Because honestly, it was about the only way to get any real life images into a computer
like the Commodore 64.
Shortly after, they did come out with the hand scanners from Logitech and what not,
but I don't think those were ever available for a machine like this.
So let's take this thing apart and see what makes it tick.
After removing the bottom, it requires a T6 torx driver to remove the knobs from the potentiometers.
Then a half-inch wrench to remove the nuts.
Once inside, this thing is surprisingly basic.
In fact, it only has 5 discrete ICs on board.
This one here is a dual timer, this is a NAND gate, this is a flip-flop, and these two are
analog comparators.
So these are all off-the-shelf components and I'm pretty sure all of these are still
available today.
You could build the board in this thing fairly easily, even today.
Well, that about wraps it up for this episode.
I don't want to overload everybody, it seems like I'm doing a lot of Commodore videos
lately, but I have a lot of neat peripherals like this that I have been wanting to show
for a long time, because they're an important part of computer history just as much as the
computers themselves.
And, so, I'll try to space them out a little bit more, though.
I would also like to mention to everybody that I'm slowly adding more and more stuff
to my website.
For example, I've now put many of the software titles that I've written for 8-bit machines
over the years, are now available for free for download on my website.
Also you can purchase the CD sound track to my channel there as well.
Thanks for watching and stick around because there's more stuff coming!



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