Posted By
IstvanV
on 2008-04-10
10:53:52
|  Re: plus4emu FLI converter
I noticed that the converted images do not look exactly as they should on my real Plus/4, and made some tests to see if the luma table (which was calculated from the TED documentation, and is also used in YAPE) is correct.
The following table shows the luma levels taken from the TED documentation ("calculated"), as well as those from my real machine (the two "measured" rows, where S is based on the voltage on the S-video output, while C is the composite output, and "Digitized1" is based on a screenshot of the composite output), the "digitized" palette from YAPE (which is based on another real machine), and VICE, all normalized to the same range as in the documentation:
Black 0 1 2 3 4 5 6 7
Calculated: 2.000 2.400 2.550 2.700 2.900 3.300 3.600 4.100 4.800
Measured / S: 2.000 2.437 2.611 2.686 2.921 3.393 3.844 4.096 4.800
Measured / C: 2.000 2.434 2.608 2.681 2.916 3.388 3.840 4.093 4.800
Digitized1: 2.000 2.431 2.600 2.679 2.912 3.387 3.833 4.086 4.800
Digitized2: 2.000 2.419 2.608 2.661 2.881 3.332 3.814 4.087 4.800
VICE: 2.000 2.438 2.613 2.700 2.875 3.400 3.750 4.100 4.800
Note that level 5 in particular seems to be too dark (3.6, while all the others are at least 3.75), and it does actually make a visible difference. So, should I change the palette in the converter and emulator to match more closely the real machines ?
Another color issue: the "green" color has a phase angle of 230 degrees in the current version of YAPE, while it is 240 on my Plus/4 in PAL mode, and 244 in NTSC mode (after conversion to YUV colorspace). In the "digitized" palette of YAPE, it ranges from 236 to 240, and the TED documentation says it is 241 (which is also what I use in the emulator sources). Since the difference between 230 and 241 is visible, I wonder which one is actually correct ?
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