Retro computer output - analogue to digital conversion

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Retrospective

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Retro computer output - analogue to digital conversion

PostThu Jul 28, 2022 9:56 am

Hello everyone, new to BM forums and proud owner of now several BM products. I have a problem with my set up with respect to recording legacy retro computer output to digital (upscaled of course to 1080p) for my new soon-to-be-launched YouTube channel.

Set up - I have a SCART-to-Component signal converter (tried two different ones - same result) that converts the SCART output signal of the Amstrad CPC6128 to Component video. This is then connected via BNC cables on back of Teranex Analogue to 12G converter.

When I power on the Amstrad, I get what you see in the attached video. It seems to be a FRAME SYNC kind of issue. Picture quality is solid though. Suffice to say connection to old school TVs and legacy inputs on older LCD monitors is SOLID. Side note: I tried an Amstrad CPC464 and the signal was PERFECT.

Amiga 1200 is perfect.

I tried a BBC Micro computer and I get a similar problem to the Amstrad. I also see "purple" artifacting in the image of the BBC micro.

I tried a Commodore 128 and I can see the image trying to sync up but then drops it - aka no display / signal on the Teranex.

Long story short is I am kind of stuck. My journey so far: I have an OSSC but the HyperDeck 4K and ATEM Extreme ISO don't see the output from OSSC (this is a known issue with it and digitisers). I tried the RetroTink 5X and this works with the HyperDeck 4K and ATEM Extreme ISO but not always perfectly. For example with the Amstrad CPC6128 the screen is stable frame sync wise but the screen shakes and moves (that's down to RetroTink and I am sure it can be fixed by them). Tried the Elgato 4K60+ and it does not work with the OSSC. works ok with RetroTink. However regardless of all other "solutions", I like the idea of trying to keep it simple. It either goes to ATEM or hyperDeck via HDMI (RetroTink) or via Teranex. I thought given all the marketing fluff that his PRO device could handle anything from the PAL/NTSC era - but not it seems old-school microcomputers. I accept that their internal video encoding logic may not be modern but it's simple. I would love for BM to adapt / modify their Teranex software to "understand" older micro-computer video signals. Or at least put in the options/settings menus ways to modify the frame sync or other parameters, etc. I am not expert in video signals or what causes these kinds of artifacts or why one model of Amstrad works fine with the Teranex and the other not. Or the Commodore 128 just completely fails to invoke a signal.

Is there anything I can buy that will "clean" up the signal before it goes into the Teranex? Frame syncing or other devices that "correct" any inconsistencies in the signal?

Anyone have any advice / experience in digitising retro computer outputs for recording?

Thanks all.
Attachments
BBC and C128.zip
This is what the BBC looks like and the initial "flickering" recorded when I turned on the C128
(322.5 KiB) Downloaded 92 times
Amiga.zip
Amiga content is perfect.
(428.55 KiB) Downloaded 90 times
Amstrad.mov.zip
This is a few seconds of recorded video of what the problem looks like for Amstrad.
(677.29 KiB) Downloaded 86 times
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Retrospective

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Re: Retro computer output - analogue to digital conversion

PostSat Jul 30, 2022 9:36 am

Interestingly I purchased a cheap 50 Euro SCART to HDMI Video converter (not the cheapest - has nice metal chassis) and it just works with any SCART input signal - routed into the HyperDeck Studio. There is nothing that does not work. The downside is that the quality of the signal is not quite as good as say the scan-line converts (RetroTink and OSSC) but looks like I am stuck with that.

I just don't understand WHY a 500 Euro broadcast quality analogue to digital converter fails most of the time to generate a stable signal. I plugged in my old SVHS player into the 50 Euro converter and it worked fine. Does it work with the 500 euro unit - NOPE - no signal.

Please, can anyone help?

I am just purchased the AJA V2Digital converter to see what that will do. Also considering the UltraStudio Mini 4K. But my concern about the Ultra is that it will do no better than the Teranex Analogue - although I think the Studio is a more modern implementation and looks like it is more configurable = plus I can stream to the Mac directly.

Any thoughts?
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oniongarlic

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Re: Retro computer output - analogue to digital conversion

PostWed Oct 18, 2023 8:49 am

Did you come up with a working solution?
Check out my free and open software:
CutePocketRemote - https://www.tal.org/projects/cutepocketremote
CuteAtum - https://www.tal.org/projects/cuteatum
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Andy Coulthurst

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Re: Retro computer output - analogue to digital conversion

PostWed Oct 18, 2023 5:35 pm

Retrospective wrote:Interestingly I purchased a cheap 50 Euro SCART to HDMI Video converter (not the cheapest - has nice metal chassis) and it just works with any SCART input signal - routed into the HyperDeck Studio. There is nothing that does not work. The downside is that the quality of the signal is not quite as good as say the scan-line converts (RetroTink and OSSC) but looks like I am stuck with that.

I just don't understand WHY a 500 Euro broadcast quality analogue to digital converter fails most of the time to generate a stable signal. I plugged in my old SVHS player into the 50 Euro converter and it worked fine. Does it work with the 500 euro unit - NOPE - no signal.

Please, can anyone help?

I am just purchased the AJA V2Digital converter to see what that will do. Also considering the UltraStudio Mini 4K. But my concern about the Ultra is that it will do no better than the Teranex Analogue - although I think the Studio is a more modern implementation and looks like it is more configurable = plus I can stream to the Mac directly.

Any thoughts?


A broadcast standard converter is defined to work within very strict timing parameters. Retro computers only need to be able to display on an old analog TV. Analog TVs accept VERY wide timing variations. Retro computers very rarely produce accurate broadcast TV signals.
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Andy Coulthurst

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Re: Retro computer output - analogue to digital conversion

PostWed Oct 18, 2023 5:49 pm

Just adding a few more details to this - explaining some of the reasons retro computers don’t produce valid signals.

1. Some don’t produce the correct horizontal timings
2. Some don’t produce the correct number of lines per frame
3. Some don’t interlace the frames.
4. Almost ALL retro computers don’t produce a valid colour burst frequency ( there is a very specific relationship between colour burst frequency, horizontal scan frequency and vertical frequency ).
5. Almost all retro computers do not produce valid blanking ( horizontal or vertical ).
6. The timing source ( a low quality crystal ) is rarely even close to the correct frequency even when new , and even more so after 40+ years.

FYI - I was a BBC broadcast engineer in the 1990’s.

The BBC had a special board for BBC micros to allow them to be used for broadcast. The board could be locked to station timing , and also produced correct timing and blanking.
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Andy Coulthurst

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Re: Retro computer output - analogue to digital conversion

PostWed Oct 18, 2023 5:53 pm

Also - the OSSC ( I have one ) has the purpose of producing a quality signal that works on modern monitors - the priority is to produce a clean signal but not necessarily to produce a signal compatible with modern digital broadcast standards.

The reason for all these “standards” is so broadcasters can have confidence that broadcast equipment works with other broadcast equipment - not random computer equipment produced to a cost rather than a specification.

( I’ll get off my podium now - and I apologise if I offended anyone)
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Andy Coulthurst

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Re: Retro computer output - analogue to digital conversion

PostWed Oct 18, 2023 5:59 pm

And - you may ask - how do I do it ?
I have a Probel Time Base Corrector - this accepts many signals - but not all.
I also have the OSSC which I feed into a Decimator - that works for some others.
And I also have a modified bare board scan converter from amazon which I modified to try and improve some of the noise problems.

All together this gets most of my ancient computers working on broadcast equipment.

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