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.