HDMI Video Card for Apple II

[cbmeeks]

I found this over on the Apple II Google Groups.

https://drive.google.com/file/d/1cm52xh ... 6e5tS/edit

I don't know too much about it, but it was announced at KFEST. Looks very promising!

[barrym95838]

John Brooks is a huge asset to the retro community, especially for the 8-bit Apples. I wish I knew how he finds the time to be so productive.

[BigEd]

Interesting!

Quote:

Targets:

• VidHD production: Oct 2018
  Price: $129 USD

Whatever tech they are using, they seem to have a fast ARM and an HDMI output (is that something which needs to be licensed? Hmm, seems so.) They are, it seems, re-implementing, rather than sampling, the 7, 14 and 16MHz dot clock modes of the various Apple II generations. (By comparison, hoglet's latest project uses a Pi and a CPLD to sample Acorn RGB data and then reproduce on HDMI. With no ADC, it's limited to digital RGB.)

[cbmeeks]

Not sure on the HDMI. It's probably so low-key that no one will notice.

Yeah, I think re-implementing the signal vs. up-sampling is a much better way (at least with my limited knowledge). In my experiences, up-samplers always have tearing, lag and other graphic glitches. Even the high-end stuff.

But I believe this product reaches down into the actual Apple memory and creates a fresh screen in real-time. I hope I'm right about this because this opens the doors to all kinds of cool stuff. Especially if it keeps a reasonable price tag.

If it could become a standard (like the F18a is for the TMS9918 world), then perhaps Apple could finally get sprites, smooth scrolling, etc. in hardware.

[BigEd]

I'm don't know deep details of Apple II, but it sounds like an expansion card maybe sees enough bus activity to be able to monitor the writes to graphics memory and so reconstruct the framebuffer content?
"Using a slot in any Apple II, it watches for graphics output, mushes it through an ARM CPU or two, and outputs it to HDMI. From text mode (40/80 cpi) to 3200 SHR. Phenomenal! And targeted at $129"
- KansasFest report

Edit: some photos in the thread

[hoglet]

This does look a fascinating project.

Has anyone come across any photos of the board?

I'm also kind of guessing that it's not going to be open source; I do hope I'm wrong on this.

cbmeeks wrote:

Yeah, I think re-implementing the signal vs. up-sampling is a much better way (at least with my limited knowledge). In my experiences, up-samplers always have tearing, lag and other graphic glitches. Even the high-end stuff.

That may well be true on the Apple II.

On the Acorn machines it's not quite so clear cut, as many games make use of various nefarious 6845 programming tricks to achieve some quite amazing effects. So as well as re-implementing the video memory, you would need a very accurate emulation of 6845, the SAA5050, the video processor, and even down to how an analogue monitor reacts to non-standard sync pulse widths. After several years of development, these things continue to occasionally catch out even the mature Beeb emulators (B-Em, BeebEm, ans JSBeeb).

That's really why with RGBtoHDMI that Ed mentioned earlier I've taken the "Up Sampling" approach. It's also been great fun seeing how far you can push a $10 Raspberry Pi. And as of today, we have the HDMI output frequency locked to the incoming video rate, with error free pixel sampling.

The Raspberry Pi, used bare metal, is actually a very nice platform for doing this kind of stuff on.

Dave

[hoglet]

BigEd wrote:

Edit: some photos in the thread

Ah, excellent. Gosh, the card does seem to have quite a lot on it.