Poor quality vga image with Chameleon 2

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Don't Panic. Please wash hands.
  • Hello all!


    I'm having a bit of a problem here with my chameleon 64 (Version 2). The problem isn't with the operation with the unit but with the VGA output. I'm getting a very smeary picture with ghosting. Unfortunatly it is hard to show this problem "on-camera" all that well although I've tried to attach some pictures below. I've tried with 3 displays (One is a DVI monitor which will accept a vga input via a vga to dvi converter); another a normal HDMI monitor (I used a powered vga to hdmi converter) and an actual monitor with vga input.


    The problem remains the same with all 3; trying to change the screenmode on the chameleon either makes the problem worse or the monitor refuses to accept the screen mode setting. In particular when I used the HDMI monitor/powered VGA to HDMI converter and tried to resolve the problem by increasing the video mode on the chameleon the result more closely resembled early 80s UHF TV output - !


    Unfortunatly I no longer have any other vga monitors around :-(


    I've attached a couple of pictures btw. I don't seem to have any connection issues btw (cables fit ok in chameleon 64's vga output port). I've also tried differnet power supplies.


    Anyone know why I'm gettng such a poor smeary vga output?



    Here's the first picture. Note the fuzzyness to the right of each character. I could not get it to show on camera but a little to the right of the white cursor there's also a ghost of the white cursor.




    Smeary picture again shown here with lots of smearing in the blue part of the image here (blue background, yellow characters).


    I did not use any "sharpening" settings on any of the monitors (only the HDMI display even had that, and it was not being used).


    ljones

  • I'll give another cable a try but I do not think that is the problem. One of the monitors I tried has its own built-in cable and works fine (for example with a rasbperry pi). This monitor had the exact same problem with chameleon 2 as did all the others.


    ljones

  • There are two problems with the VGA output:

    - The pixelclock is currently fixed, that means unless you are using the default 800x600x72 mode, the pixelclock will not match the exact requirements of the VESA modes, and thus the monitor might get confused about it and not sample it correctly.

    - The sync polarity is wrong in some modes.

    - Unless your monitor has a native 800x600 resolution, it will do scaling and everything bad connected to it. Depending on how picky it is on clock detection and sync phase/polarity, it will even do more bad things.


    That said, Peter is currently working on the VGA output part of the core, essentially rewriting everything, so we have a async clock now, perfect matching pixelclocks and syncs, and essentially much better compatibility (hopefully). So chances are the next update will fix most (hopefully all) of those related problems.

  • Yeah, this sounds great. Hopefully this makes TC64 working with a Sony KDL-20B4030 TV. This TV got some noticable mentions at Forum64.de for being a quite good display for Amiga and C64 and supplying a lot of input connectors. But with current firmware none of the TC64 VGA modes is compatible with this TV and alas this also applys to the Minimig core.

  • Just so it's not forgotten, the image quality is still poor and exactly the same as shown in the pictures posted by the thread starter. Ghosting/shadowing. Same poor quality the ECS V2 has. ECS V1 and TC64 V1 does not have this poor quality.


    Hopefully Jens will come out with his patchboards for ECS V2 and TC64 V2. Poor picture quality will not be resolved without these patchboards. No monitor or VGA cable will resolve these ghosting/shadowing/poor quality image issues.

  • Was there any fix for this in the end? Pretty much my chameleon 64 v2 is sitting around unused; tried several monitors including one on the wiki I got second hand but working (the Dell 1708FPf) but still the same smeary/ghosting on video in all modes.


    ljones

  • I do have an upgraded circuit, but making this a patch-PCB for people experienced with a soldering iron is a different story. I'll attempt that first for Indivision ECS V2, and if that works out fine, I'll attempt the same for Chameleon V2. No promises on a timeframe, though.

  • Something strange happened yesterday. So I have a bunch of different VGA cables. Including some thick ones. all have ferrite beads on both ends. Strangely enough I get the best results with the ones that come with the LCDs. The not so thick ones with blue VGA plugs and ferrite beads on both ends.


    Anyway, lately I thought my BenQ BL912 was showing a lot less ghosting VS my BenQ BL 702As. That was until yesterday when I found out the specific cable I was using for my BL 912 caused this. This cable is identical to the one I was using on my BL 702A. I have a bunch of these cables. But the one I am using for the BL 912 shows the least amount of ghosting.


    Anyway, for a short while yesterday the ghosting was completely gone when using this cable. On both monitors. Now the ghosting is back again. to the same level it was showing before. The other cables still makes it worse. Very strange. I don't understand why the ghosting was completely gone for a little while. As I was switching the cable between the monitors the regular ghosting was back. Very strange. Like the stars was aligned for a moment.


    At the same time I see the ghosting even if I use a VGA to HDMI converter plugged directly into the TC64 V2 (No VGA cable). But the fact that the ghosting was completely gone for a moment when using this random VGA cable makes me think there must be some kind of simple fix to this. It shows that the TC64 V2 can show a ghosting free picture for me. Something must have caused it.


    This was done in cartridge mode using 768x576@50Hz.

  • Kind of - a new analogue front end has been rolled out with Indivision ECS V3, and this appears to solve the issue that becomes visible on Samsung monitors only. So we have a circuit now that can deal with those funny inputs - next step is to find some time to make patch-boards for older Indivision ECS V2 and Chameleon V2.