JimLyon

I'm trying to get my K301 screen working well in 800x480 mode. I've tried everything I've seen in other threads, as well as everything else I can think of, and every set of timing parameters leave me with either horizontal or vertical miscalibration artifacts.

Attached are two bitmap files that clearly show the miscalibration artifacts. One is sets of vertical lines separated by varying amounts of white space, and the other is horizontal lines in a similar pattern.

Does anyone have a set of timing parameters with which you can display both of these files without glitches? If so, could you please post them? (Under Windows, your best bet is to open them under Paint, so as to avoid any software attempts at scaling.)

Thanks in advance,

-- jim

Attached Images

  

wywywywy

Same here.

Even though I've got 800x480 working, it doesn't seem to be 1:1 pixel mapped, like you said.
Makes me wonder whether this screen is actually 800x480, because 720x480 displays really nicely.

JimLyon

It's pretty much gotta be 800 x 480: When I use the Windows XP default 800x600, I don't get any horizontal repixelation (but do get vertical). When I use any of several timings from other threads on this forum to have 800x480, I don't get any vertical repixelation, but do get horizontal.

I just haven't been able to find timings that doesn't repixelate either.

JimLyon

After much experimentation, I now believe it's impossible to get true 800 x 480 on a K301. The K301 seems to use the following algorithm for pixelation:

1. Count the number of scan lines, including retrace. Choose a standard vertical resolution that's somewhat less than the count. Standard vertical resolutions include 480, 600, 800, 960, 1200. If the chosen value is other than 480, resample the incoming lines to map them to 480.

2. Multiply the vertical resolution by 4/3 to get the horizontal resolution. Resample the incoming data for a line into this many pixels, and if the number isn't 800 resample it again into the physical 800 pixels.

3. The actual values of scan rate, front porch, sync pulse width, back porch don't matter much. If you use almost anything within reason, the Auto Config function (accessible via the buttons on the front panel) will adjust the picture to fit perfectly.

So, if you feed it 800 x 480 data, it will resample the 800 across into 640 pixels, then resample them back to 800 pixels. I wrote a short program to simulate this effect, and the results (on my desktop) match almost exactly the results I see visually on the K301.

In short, if you want pixel-perfect fidelity, stay away from the K301!

-- jim

PS: The above is entirely an exercise in phenomenology, and should not be relied upon as a spec. If you find evidence that contradicts the above, please let me know.

wywywywy

Nice analysis, but quite disappointing to hear