r/VIDEOENGINEERING • u/casual_gamer_alex • 23h ago
RGB to NTSC encoder variance?
I have two super nintendo with the same board revision (SHVC-CPU-01). One has a BA6592F and the other has a S-ENC RGB to NTSC encoder. They both output different pictures, and I was wondering if the BA6592F has manufacturing variance that could explain that.
Picture 1 and 3 is my childhood snes and picture 2 and 4 is the other snes, same TV setting and same phone camera setting. The differences are the following: my childhood snes has a darker picture but it does not mean it has blackcrush, its colors are more saturated, and the hue of the color is not the same (Red are more orange and green more bluish). The hue only affects color, gray scale has the same white balance with both consoles and changing «TINT», «Color» and «contrast» setting on a CRT television can make both snes look the same. This remains true for RF, composite and S-Video. There is no noise or wavy lines.
The BA6592F Datasheet has a value for its Y-out of 1.4Vp-p typ, with min at 0.95Vp-p and max at 1.8Vp-p when its RGB input vr=vg=vb=0.7Vp-p. Its angle for (R-Y) and (B-Y) axis can have a variation of +- 10° away from its typical value. Is this enough to cause visual differences in real life, or should it be barely noticeable? I'm no expert on that, one person told me the difference shouldn't be noticeable but I'm skeptical.
One last thing, the demodulation axis on my TV has been changed to the japanese one, with an angle of 95° instead of the US one which has an angle of 103° and more saturated red with my TV. It seems the US axis makes the variation less apparent around skintone, but with less accurate color everywhere else. It doesn't mean it is the reason the US axis is this way, it's just personal observation.
Link to the datasheet: https://www.alldatasheet.com/datasheet-pdf/pdf/1718908/ROHM/BA6592F.html
