Can someone recreate better video from Intellivision...?

[Uzumaki]

It can only support composite at best with a mod, and most people have reported no change or worse quality than stock RF. I looked at schematic (Sylvania model, same as all other models except Inty 2) and it's a convoluted mess with weird data and address line. If someone could get a detailed information on AY-3-8915 or AY-3-8900 maybe it'd be possible to dechiper how the video is generated. All of the IC's used in Intellivision series are long obsolete and chances are it'd require some fancy circuit such as fpga.

 

Datasheet on the video chip: http://www.avoidspikes.com/dsplib/chips/ay38915.pdf shows that video out are in fixed 4-bits binary output through resistor ladder to create raw composite video. Unfortunately I don't have the knowledge or expertise to create something that can read the signal, interpret it for color and brightness, and provide 2 analog output (or RGB even)

 

A challenge for someone maybe? I'd love to get a much improved video mod because Intellivision is one of only 2 game consoles I have that are still stuck on ugly RF or barely-better composite (NES being the other) and my goal for sometime this year is to have nothing plugged into composite port of my TV.

[Uzumaki]

Another chip: http://www.avoidspikes.com/dsplib/chips/ay38900.pdf since it's what connected to the video chip.

[Uzumaki]

So no one knows? I would think someone could cook up a FPGA that reads from the data to determine which one of the 16 colors, and generate RGB output plus timing to match the source? w

[+grips03]

Matt made a F18A for Colecovision (VDP in FPGA with VGA out), perhaps he could do for same for Intv. Has anyone asked him?

[JohnPCAE]

I don't have the EE experience to build a replacement circuit (when you major in Physics they only teach you enough electronics to get yourself in trouble), but I learned a lot in the last hour or so. I found this info on Wikipedia:

 

http://en.wikipedia.org/wiki/YIQ

http://en.wikipedia....tude_modulation

http://en.wikipedia....osite_Video.svg

http://en.wikipedia....IQ_IQ_plane.svg

 

The short of it is that NTSC color information is encoded with two signals, I and Q. They're plain sine-wave signals and have the same frequency but are 90 degrees out of phase, and the encoding consists of varying their amplitudes. The table in the AY-3-8915 PDF shows how inputs from the STIC translate to maximum and minimum values for the I and Q signals for each pixel.

 

I then did a little analysis by calculating the center and amplitude of the Q and I signals:

Color code Color Q I Qc Ic Qa Ia

------------------------------------------------------------------------------------

0 Black +3 .. -3 -3 .. +3 0 0 6 6

1 Blue +5 .. -9 -13 .. +1 -2 -6 14 14

2 Red +8 .. -4 -0 .. +12 +2 +6 12 12

3 Tan +4 .. -12 -4 .. +12 -4 +4 16 16

4 Grass Green +3 .. -11 -8 .. +6 -4 -1 14 14

5 Green +3 .. -13 -11 .. +5 -5 -3 16 16

6 Yellow +9 .. -15 -11 .. +13 -3 +1 24 24

7 White +13 .. -13 -13 .. +13 0 0 26 26

8 Gray +9 .. -9 -9 .. +9 0 0 18 18

9 Cyan +8 .. -12 -13 .. +7 -2 -3 20 20

10 Orange +9 .. -9 -4 .. +14 0 +5 18 18

11 Brown +4 .. -8 -4 .. +8 -2 +2 12 12

12 Magenta +13 .. -3 -5 .. +11 +5 +3 16 16

13 Light Blue +12 .. -6 -12 .. +6 +3 -3 18 18

14 Yellow-Green +5 .. -13 -9 .. +9 -4 0 18 18

15 Purple +10 .. -2 -5 .. +7 +4 +1 12 12

------------------------------------------------------------------------------------

Blanking +3 .. -3 -3 .. +3 0 0 6 6

Color Burst +1 .. -5 -1 .. +5 -2 +2

Sync 0 0 0 0 0 0

Test 0 -15 .. +15 0 0 0 30

 

 

I think the amplitude controls the color intensity; the centerpoint (Qc, Ic) definitely controls the hue as seen on the YIQ graph in the fourth link above.

Edited April 26, 2013 by JohnPCAE

[+grips03]

this is a PAL Intellivision write up, does US use same components?

 

http://gamesx.com/wiki/doku.php?id=av:intellivision_pal

[Uzumaki]

Sadly no. I saw that page but some parts didn't match the schematic for NTSC model, and PAL model costs an arm and a leg if you can find one on eBay.

 

I looked to see if I could find a full schematic of PAL Intellivision to see how it differed but I couldn't find any anywhere. The link above for RGB mod only covered a tiny part of video board, I'd need a full version. Any idea?

 

I found an older post about Intellivision color and had color table with RGB value:

http://atariage.com/...e/#entry2611965

Edited April 26, 2013 by Uzumaki

[JohnPCAE]

The "ideal" solution would be a drop-in replacement for the AY-3-8915 that provided extra outputs, though this is of course easier said than done. Is the same chip present on PAL? From what I can tell, while PAL and NTSC use different means of encoding chroma in the composite signal, their color spaces are very similar--merely rotated 33 degrees relative to one another.

 

Since the 8915 controls the color palette, if we had an 8915 replacement we could look at doing some really cool things like programmable palettes, though I have no idea what the best way would be to get programming information to it.

[Uzumaki]

I haven't been able to find a good quality PAL schematic, the only one I found looks like it was scanned through a business card reader. I do know that PAL (both UK and Australia model) has extra daughterboard on the back of mainboard that can do RGB with mod but without a schematic I can't tell if it could be adapted for NTSC model or not.

 

A drop in replacement would be nice but it might be rather hard if there's no detailed information about 8915's internal or a chip schematic. All I know is it has 5 lines from other CPUs, 2 lines for external clock (double NTSC frequency), 1 line out to other chip (NTSC frequency or 1/2 the oscillator speed) Vdd (test reset, always connected to 5v on consoles), Vss, ground, and finally 4 output that are fed through resistor network to generate composite video.

 

On 8915, input pins labeled V1 to V4 are 4 bit digital signal that select one of the 16 possible colors, V5 (when high) is used to trigger blanking, sync, or color burst. Maybe a FPGA that can sniff that 5 lines and generate RGB output? I wonder if that's how PAL Inty works?

[First Spear]

Is there any new anything happening with this? I'm ready to buy almost anything to get decent video/audio out from my Intellivision.

 

 

Thanks.

[scalpel]

Is there any new anything happening with this? I'm ready to buy almost anything to get decent video/audio out from my Intellivision.

 

 

Thanks.

 

You need a RGB (Peritel version) of the Intellivision (Pal SECAM only) ^^

[+Lathe26]

Or buy an ordinary PAL Intellivision and upgrade it with the Zoe kit to a Peritel RGB:

http://www.nightfallcrew.com/30/11/2013/zoe-interface-prototype-the-best-video-output-for-your-intellivision/

[scalpel]

 

You need a RGB (Peritel version) of the Intellivision (Pal SECAM only) ^^

 

Actually, the peritel intellivision version works on all TV with a scart.

 

I will trade or sell one loose version and one CIB.