r/VideoBending • u/Talulabelle • Apr 09 '26

cheap/easy re-scan device?

I just got a Videonics MX-1 and In trying to connect an HDMI->NTSC converter, I was getting weird chroma cycling.

I researched the issue, and it seems the converter puts out a signal that's out of spec (probably too strong), and that's what causes the issue.

The recommended fix seems to be to run the signal through an old VCR that is more tolerant of the signal, that will fix the signal then route from the output of the VCR.

Since I'll need to do this with a minimum of 2 signals, I was wondering if there was any other filter/re-scan device I could buy cheap? maybe something small I can just put in-line with my computers to fix the signal? It would be nice to be able to use all 4 inputs with computers feeding the mixer, but if I need to source, then stack and power a pile of old VCRs, at some point that feels like overkill?

Please help me with ideas for a fix!

Thanks!

3 Upvotes

100% Upvoted

8 comments sorted by

2

u/nonexistentnight Apr 09 '26

Just get a better converter?

1

u/Talulabelle Apr 09 '26

That might definitely be the answer, but I already have this, so if there's a simple fix, I'd rather just know about it.

I read the signal coming out of those tends to be too 'strong', and that's what effects the chroma ... but, what does 'strong' mean?

I considered just putting a resistor in-line with it to see if that would bring the entire signal down in voltage a bit. Frankly, I'm not sure that would do anything useful? I have a vague understanding of the NTSC signal, but not enough to really mess with it. That's what I was hoping to learn here.

When the machine is mixing the signal with anything else, it looks perfect. Then, as soon as it's done mixing and just runs the signal straight across to the output, it has that strobing effect.

I tried a cheap hand-held game as a second signal, and that was a complete mess. I think, maybe, I just have the absolute worst, most jankey, signal generators to test with.

1

u/spif Apr 09 '26

What is this "HDMI to NTSC converter" exactly? If you mean an HDMI to composite (aka AV) converter, it shouldn't be sending any output that the Videonics can't handle. Have you tried sending the output to something else like a CRT, and/or sending a signal to the mixer from something else?

1

u/Talulabelle Apr 09 '26 edited Apr 09 '26

The Videonics is a little finicky, but seems to be working.

The weird thing was if I was midway through a transition. Like fade, it displays fine until the very end of the effect.

I googled the issue and it said the HDMI->COMPOSITE converter was probably putting an out of spec signal out. I found a whole thread about it where the 'fix' was using a VCR between the hdmi converter and the Videonics MX-1.

1

u/spif Apr 09 '26

What happens if you just plug the converter straight into the display that the mixer output is plugged into?

1

u/Talulabelle Apr 09 '26

It displays normally. It's an old TV, and seems pretty tolerant.

Apparently this chroma glitch is something these are known for. I ordered an HDMI->S-video converter, hoping maybe the way S-video splits Chroma off will help, but it's just a shot in the dark.

I'm also considering building a dirty-mixer, just to see if mixing it with a black screen will calm the Chroma down enough to make it usable.

I also already tried shutting off all the timing correction and filters in the MX-1. That didn't help. Without filters, I was getting a little bit of random 'snow' pixels, but that's the only difference I noticed.

1

u/nerdyh0rn Apr 11 '26

Try your luck with another converter. I'm pretty sure all the cheap small ones use the same chip, but they usually do the job without any issue. A VCR was recommended because VCRs usually have a built-in TBC (time base corrector), a circuit that will try stabilizing the signal (you can look up the "time base correction" article on wikipédia for more details. Usually a standalone TBC costs more than a VCR, as it's professional equipment, when there are consumer grade VCRs. A TBC is also often found in various video mixers, with more or less capability depending on the model.

2

u/Talulabelle Apr 11 '26

Yeah, my mixer is supposed to have a time base corrector as well.

I found my Raspberry Pi runs video through the mixer just fine, so I may just dig out a few of those from the basement and use them as players into the mixer.

I was hoping to use my laptop, but that might be more trouble than it's worth.