Best way to capture Mac II video output while still outputting to original 13" CRT?

[esselfortium]

I have a Mac II with a 13" AppleColor RGB CRT. I have a Toby card and also a Radius PrecisionColor Pro 24XP (which doesn't seem to get along with the AppleColor display, sigh, though I've confirmed it works). I'd like to get the Toby's video output into a digital video form that my modern PC can see, while still outputting to the AppleColor so I can sit at that desk and use the Mac normally.

My initial thinking was that I'd use adapters to go from DB15 to VGA and back so I could use a powered VGA splitter and a VGA-to-USB device to effectively mirror the Mac's video output to the CRT and the VGA-to-USB, and thus have video on the CRT as usual while also capturing the same video digitally on my modern PC. The digital video capture worked (albeit with terrible washed-out color and even worse pixel scaling... I'll potentially need a different capture device), but the AppleColor didn't want to display anything at all from that adapter setup. And I can hook up the capture device to the PrecisionColor, but there's no way to get both video cards to output the same video, so that's also less than helpful for my needs. So I've ordered a DB15 Y-splitter but I'm already realizing that this is going to inherently reduce the video quality, since I couldn't find a powered DB15 splitter like the VGA one.

The end goal here is to do a music composing stream on the Mac II, and possibly other streams on there later, by sending video to my PC and letting that handle the actual streaming. I've already got the DAW software and MIDI hardware set up and working for the music composing side of things on the Mac II.

Is there a good, known approach for this before I spend more money on trial-and-error? I'd prefer to keep the AppleColor and avoid having to just use a modern flatscreen on there, it would kill the vibe a bit

Thank you!

 

[Innes]

I've had a powered VGA splitter from startech knocking about for a while but never gotten around to trying it out, so i'm unsure how that would actually effect the quality, but i've no idea if the VGA signal from the splitter is somthing the monitor's DA-15 port can work with.

I would suggest that getting capture quality to an acceptable level should be the first priority, then you could still do a nice stream even if the Mac is running headless.

From my own experience, this can only be achieved with a half-decent upscaler like an OSSC. Doubling the pixels with hardware stops single pixels bleeding into mush when its encoded/compressed into digital video, and offers video quality some resilience to online platforms (and users on them) changing video/stream resolutions and bitrate to their own preference.

 

[finkmac]

pretty sure you can add a second video card and set it to mirror the first card?

 

[LaPorta]

Didn't someone here make a Nubus HDMI output card?

 

[Innes]

That this? https://github.com/MelkhiorVintageComputing/NuBusFPGA

 

[esselfortium]

pretty sure you can add a second video card and set it to mirror the first card?

Mirroring isn't possible here, AFAIK, unless there's a very hidden setting or extension for it.

Running the machine headless is an option, yes, though I'd really prefer to avoid it if possible.

 

[finkmac]

iirc you drag one display over the other?

 

[ymk]

Do you need to live stream or just capture?

The picture quality with a Y cable can vary depending what is plugged into which end of it.

Having the trunk end plugged into the source isn't always best.

 

[esselfortium]

Do you need to live stream or just capture?

The picture quality with a Y cable can vary depending what is plugged into which end of it.

Having the trunk end plugged into the source isn't always best.

Live streaming is the goal. And that's interesting/surprising to hear about the Y cable... how else can it be used?

iirc you drag one display over the other?

No luck. I can drag them beside each other, but not onto each other.

 

[ymk]

Live streaming is the goal. And that's interesting/surprising to hear about the Y cable... how else can it be used?

Ok, I was going to recommend a capture box, but that won't help you.

You can put the source on a branch and sinks on the trunk and branch. If one of the sinks is sometimes off or detached, it's best to put it on the trunk.

What you definitely want to avoid is having the source on the trunk with an unconnected branch. This usually causes reflections that appear as ghosting.

 

[zigzagjoe]

There's no support for mirroring on classic mac OS outside of a few oddball powerbooks and that does some nasty voodoo requiring hardware support to make it work. There might be software that does mirroring, but performance would be abysmal as it's all software copies between devices without awareness of dirty regions. You could technically do something like MacVNC but that suffers from the same inability to track dirty regions and a Mac II even accelerated would suffer badly especially if you're actively working.

So, a hardware approach is required. A Y cable may or may not work due to analog video signalling being a current loop, modern LCDs can deal with reduced signal amplitude to some degree but a vintage CRT is probably not going to give a good picture. Sounds like you already ran into this. An active VGA splitter would the best approach here, but you'd need to adapt it to/from VGA on both ends in order to use your vintage monitor.

 

[esselfortium]

There's no support for mirroring on classic mac OS outside of a few oddball powerbooks and that does some nasty voodoo requiring hardware support to make it work. There might be software that does mirroring, but performance would be abysmal as it's all software copies between devices without awareness of dirty regions. You could technically do something like MacVNC but that suffers from the same inability to track dirty regions and a Mac II even accelerated would suffer badly especially if you're actively working.

So, a hardware approach is required. A Y cable may or may not work due to analog video signalling being a current loop, modern LCDs can deal with reduced signal amplitude to some degree but a vintage CRT is probably not going to give a good picture. Sounds like you already ran into this. An active VGA splitter would the best approach here, but you'd need to adapt it to/from VGA on both ends in order to use your vintage monitor.

Thanks for the thorough reply. I do have an active VGA splitter, but I haven't been able to get the CRT to recognize anything that's gone through the VGA/DB15 adapters I have, with or without the splitter involved. Do I need dip switches on both ends of the conversion?

 

[zigzagjoe]

You'd definitely need it on the output from the video card so it outputs something appropriate for the CRT. I'm not sure how (or if?) the CRT senses connection, but you might need something to fox it on the other end too. That'll probably be a DIY affair.

 

[esselfortium]

I see. I have them on the output from the card, but not on the other end.

 

[ymk]

Also, if you are streaming from one machine to another, you have to be aware of ground loops which can result in audio buzz/hum and display artifacts.

Using a cheater plug on the Mac and its monitor is probably the easiest way to do that. Those items would then be grounded through the streaming PC. Same applies to powered monitor speakers, which can introduce ground loops on unbalanced inputs.

 

[esselfortium]

Thanks. I've already got the audio side of things sorted, thankfully, but that's good to know about the display artifacts.