exxos's Atari, Amiga & retro forum

Conclusion from my video and summarized nicely by Ian Stedman here..
There is no way for the Green lines to flow to the DB23.

Is the U36 a video mixer, mixing the FMV and RBG together. Or is it just a video switch choosing which video to output to the video circuit?

If it is just a switch, then it would be simple enough to just re-route the signals AR_EXT, AG_EXT and AB_EXT to be the new RGB output for the Video port when a FMV-module is connected.

Or am I oversimplifying things here?

AR/AG/AG would be analogue signals, not digital RGB. You would need to try and find where digital RGB is in the FMV and try and switch it to the DB23.

Whole thing seems kinda pointless (like most retro :) ) to me. But hey if you're having fun!

Does anyone know if a 68060 would be able to decode VCD in software in real time? Would make the FMV redundant...

The U36 (4066) is a simple quad analog switch and it doesn't do any mixing of signals.

When _EXT_VIDEO is low the Amiga video output is disabled and the FMV outputs video.
When _EXT_VIDEO is high the Amiga video output is enabled and the FMV does not output video.

It would be logical that the FMV has a 4066 quad analog switch with an inverted _EXT_VIDEO signal, or some kind of chip that goes high impedance if no video is played by the FMV.

<SNIP OFF TOPIC HDMI DISCUSSION REMOVED>

dalek wrote: 23 Jan 2020 11:00 AR/AG/AG would be analogue signals, not digital RGB. You would need to try and find where digital RGB is in the FMV and try and switch it to the DB23.

Whole thing seems kinda pointless (like most retro :) ) to me. But hey if you're having fun!

Does anyone know if a 68060 would be able to decode VCD in software in real time? Would make the FMV redundant...

Why do you need the digital RGB signals? the output from the Kipper and TF Risers is analog RGB anyway! so in theory you could put a quad analog switch on the riser to switch out the CD32's native rgb output to the DB23 and insert the FMV signals instead, you just need to make sure that you also add the necessary resistors to provide the level shift of the signals...simples.

I'd make a small circuit on the riser identical to the one on the CD32's schematic.
U32 is a SN74HC4066, which is still available from Digikey and Mouser. The pins are there and pretty sure it would work.

dalek wrote: 23 Jan 2020 11:00 AR/AG/AG would be analogue signals, not digital RGB. You would need to try and find where digital RGB is in the FMV and try and switch it to the DB23.

Whole thing seems kinda pointless (like most retro :) ) to me. But hey if you're having fun!

Does anyone know if a 68060 would be able to decode VCD in software in real time? Would make the FMV redundant...

The DB23 does not use the digital signals. Look at the schematic for my riser or kipper's riser.

Its far from pointless. First It gives us a way to do FMV via DB23 which is useful and second it gives a general way to do this kind of thing in the future. including potential video overlay on a window (as you can time the switch in hardware). It also removes the potential for me having to answer endless questions about my riser in future if it just works.

theq wrote: 23 Jan 2020 17:01 I'd make a small circuit on the riser identical to the one on the CD32's schematic.
U32 is a SN74HC4066, which is still available from Digikey and Mouser. The pins are there and pretty sure it would work.

Exactly what i discussed on stream last night. Nobody watches or listens.

terriblefire wrote: 23 Jan 2020 17:34 Exactly what i discussed on stream last night. Nobody watches or listens.

I just watched your stream after I posted. Was too tired last night, sorry :?
Luckily analog signals are easy to work with :D

Typing this as I watch the stream from last nite, looks like you have figured what is going on, looking forward to your
next stream

Just to clarify for the people who not looked at the schematics for the FMV unit
There is a 24bit RGB feed from the C-Cube Mpeg chip that goes into a STV8438CV video DAC
the CD32 (AR/AG/AB/Sync) signals are also fed into this and everything is sent out on the pins (AR_EXT/AG_EXT/AB_EXT)

The STV seems nifty in that it can do PAL/NTSC and also syncs the two signals together, this is why
I was wondering if it could be used as a very basic PAL/NTSC 24bit display using a block of SRAM instead of the C-Cube Mpeg chip
on another thread. I see some experiments going on with the STV here on Exxos for the Atari machines.
sampling the (AR/AG/AB) with an ARM chip sounds much easier than doing it with the STV

Didn't know the schematics from the FMV were online.

You are right, there is a switch in the STV8438CV for Amiga / C-Cube output.

Does that mean Ext_Video is always low if an FMV unit is placed?, makes sense....
Could not find it in the crappy PDF schematics i found , maybe there are better ones out there?