Exploring the BBC Micro's video outputs on a digital oscilloscope
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- เผยแพร่เมื่อ 22 ก.ค. 2024
- Using a Rigol DS1054-Z Digital Storage Oscilloscope to examine the RGB and monochrome composite video outputs on a BBC Master computer. Looking at the video trigger, RGB component levels and horizontal and vertical sync pulses.
- วิทยาศาสตร์และเทคโนโลยี
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It is a pity that you get very little views for such interesting content! I subscribed! Cheers!
Criminally underrated video. This is the most helpful oscilloscope video I've ever seen.
@Estefana Denby this shit needs to stop
@@rzeka I reported it
Great video. Yes, a review of the two other video converters would be very useful.
Very well-made video! It's absolutely astonishing how you only have 146 subscribers, it hurts my brain trying to understand such a low subscriber count with this level of content.
I've made that 147. :)
Thanks very much! I try to do videos about things that I haven't found any other ones about, or they don't cover some of the things I think are important. Looking at analogue video signals over an oscilloscope is pretty amazing and I was shocked there aren't many videos about it.
This is absolutely brilliant. This is the single best explanation and demonstration of video signals and oscilloscopes I’ve seen on TH-cam. Thanks for making it 😊
Thank you so much for this! As someone who owns a number of BBC micro's and a Rigol 1054Z I found this really interesting.
Excellent video, very clear and accurate explanation of oscilloscope use, keep up the good work!
c'est extremement interessant, merci beaucoup!
Thanks for this , really great vid.
Great video. Thank you!
This was a fantastic explanation of how the video works and how you can look at it with those scopes! Thanks so much! Would be interested in knowing more about the converters you mention at the end too as was contemplating an RGB to scart but sounds like they might be better options.
The RGBtoHDMI is the best and most flexible, especially as it supports a whole pile of different computers now. It's all open source here:
github.com/hoglet67/RGBtoHDMI
... and there are several videos about them on TH-cam: enough that I'm not sure if I should make one myself, as I usually go for making videos other people haven't.
I don't know if anyone is making them right now, though: I think the guy who is doing most of the work isn't well at the moment, but some other people have been running off small batches. They are fantastic, though: the video from 80 column mode on my C128DCR is captured from that.
The other unit (the BBC2DVI) is fine, although it's more expensive and not as flexible, as it only supports the BBC Micro and Electron. I tend to use that one on my Electron.
Since I did the colour composite mod on a couple of Elks (Iss 4 and Iss 6) they're both 'noisy' on an LCD display (I know the Iss 6 has a dodgy clock, but the 4 was pretty good until I bridged LK 4) I think this has inspired me to use my pocket scope on the problem.
Hello, can anyone explain me why he needs to add a dummy load on the bnc cable, what is its purpose here ? thanks ! :)
It's not a "dummy load, " it's a terminator. Very briefly, if you send an AC signal down a wire, you'll get reflections back from the other end, and these delayed reflections will end up combining with the output signal to change it. The terminating resistor stops these reflections.
All monitors have this termination built in. You'll notice that when he connects the composite signal to a monitor in addition to the 'scope he removes the terminating resistor from the 'scope, which is now in the middle of the video cable; the monitor is now providing the termination. Some monitors allow this kind of pass-through as well; they'll either have a switch (labeled "75Ω" and "Hi-Z" or similar) that you set depending on whether you're passing the signal through to something else with termination, or they'll automatically switch out the termination when you plug a cable in to the pass-through output jack.
If you want to delve deeper into the details, the Wikipedia article on electrical termination is one place you can start: en.wikipedia.org/wiki/Electrical_termination
@@Curt_Sampson Big thanks Curt ! Ill go and read on this, cheers !
bought the same device for the same reason lol xD
Hey! You're doing something wrong! Seriously though, for someone who wasn't trained in electronics you are doing just fine. I worked on Beebs 40 years ago. Wonderful machine .
Brilliant video. One thing I would like to clarify, though with reference to interlace on/off in mode 0-6 (non-teletext). It would be easy to get the impression that, with interlace off one is losing out, that there is some part of the picture generated but never seen. This is not the case at all. The vertical resolution of the BBC micro graphics modes is 256 lines and those same 256 lines are send in every field regardless of the interlace setting. What the interlace setting does is affect where on the TV/monitor they appear, i.e. either in same position twice in a row or one row up/down compared to the previous frame. Teletext is different in that the SAA5050 chip was designed for TVs and generates a full interlaced output, i.e. the two fields, even with a static display, are different.
16:46
there's no provision for progr. scan in analog pal signal.
15.625khz would need to be doubled to get 50fps.....my oh my....
hmmmm......
Indeed. It confused me, which is why I wondered what it was: they call it "progressive scan" in the Advanced User Guide (although I think they just call it "Interlace off" in the User Guide).
When I turned interlace off, it made me realise it was just displaying one of the two fields all the time and this is why we got the black scanlines that everyone likes to keep for the authentic retro experience. But it's not what I would call progressive these days, unless you think of it as 288p.