Talk:Myths

- An offhand comment. Wouldn't be better to change "NTSC NES picture" term into "NTSC NES PPU output"? Perhaps the second one sounds more technical than the original though. A NES picture could be anything like the straight thing: a picture of a NES unit, for example. When you say "PPU output", we have something more concrete. Yup, it's a picture, or "frame", but not "a picture of the NES", anyways... :) --Zepper 23:11, 2 February 2011 (UTC)

All three color emphasis bits with color 0D

According to my interpretation of various posts in this forum thread: sony trinitron + color emphasis bits = scrambled image?, if you use all three color emphasis bits and use color 0D, that color's signal may dip too low and confuse some TVs:

In the first post, GradualGames says he used all three color emphasis bits to dim the screen and got "an extremely ugly bunch of scanline artifacts" on his Sony Trinitron. In a later post, Sdwave says he also saw "some bending" using one of the palette demos on a Trinitron and suggested using 3F [= 1D*] for black instead of 0D. Later, GradualGames confirms using 0E [= 1D*] instead of 0D got rid of the artifacts.

*According NTSC video, the xE and xF colors send the same signal level as 1D.

Lidnariq points out that mathematically, even color 1D with all three color emphasis bits dips lower than the normal black:

If all preemphasis bits are set, then color 1D ("black") becomes blacker-than-black and 01-0C no longer decode to a valid RGB color from the received YIQ values (Their brightness is approximately equal to unattenuated color 1D). So if it looks like scanlines restarting all over the place, maybe that's why?

But based on Sdwave's and GradualGames's comments, 1D with all three color emphasis bits was fine on their Trinitrons.

--Bavi H (talk) 21:10, 23 June 2013 (MDT)

Color emphasis does not get applied for phases $xE or $xF, and it similarly does not get applied during horizontal (x=270-327) or vertical (y=241-261) blanking. --Quietust (talk) 17:23, 24 June 2013 (MDT)

Then someone's going to have to make a test ROM to run on an RGB system that displays emphasized $1D on a field of $0F to see how readable it is. --Tepples (talk) 17:41, 24 June 2013 (MDT)

I think I remember someone mentioning having a complete set of Kevtris's 2C03/4/5 dumps except for the "grey"scale dump for one of them; I'm pretty certain on those PPUs it indicated colors xE and xF being collapsed to x0 when the bit was set. ("snarky quotes" because scrambled palettes cause it to not necessarily be grey) I don't know if the greyscale bit is masked with the same flag as the emphasis bits, though. —Lidnariq (talk) 19:51, 24 June 2013 (MDT)

It doesn't tell you what it does with emphasis bits though. I too agree someone should test the function of emphasis bits of $xE and $xF on RGB systems (such as a Famicom Titler or Famicom TV). It would be useful to know, if making a emulator, hardware clone, or a game that uses the emphasis bits. --Zzo38 (talk) 01:47, 25 June 2013 (MDT)

Quietust, thanks for pointing out that using the emphasis bits doesn't attenuate the xE and xF colors, I didn't notice or remember that part of the NTSC video page. Everyone else, I was talking about an NTSC PPU sending signal to an NTSC TV, not an RGB PPU sending a signal to an RGB monitor. My original point was that the Myths page says

Myth: Enabling more than one color emphasis bit at once will damage the PPU, or at least cause the TV to lose sync.

I agree it's unlikely that enabling multiple emphasis bits will damage the PPU, but according to the forum posts I mentioned, it does seem possible to confuse a TV's line sync if you use all three color emphasis bits and color 0D. And as Lidnariq posted, mathematically 1D is lower that the black level, so perhaps using it with all three emphasis bits might confuse some TVs too?

(Above, I misbelieved the xE and xF colors would also be attenuated and so they'd have the same level as an attenuated 1D, so I misinterpreted Sdwave's and GradualGames's comments as equivalent to saying 1D was a safe color to use with all three color emphasis bits. Now I understand the xE and xF colors aren't affected by the color emphasis attenuation, so it's clear they have the same signal level as an unattenuated 1D and they're safe to use with all three emphasis bits. It's not clear how the attenuated 1D level behaves with actual TV (I didn't see 1D mentioned when the posters described problems), but mathematically I can see it might be wise to avoid it.)

If others agree the forum posts are describing line sync problems (or can recreate the results), maybe the Myths page can be revised to clarify it's possible to confuse (some?) TV's line sync when using all three emphasis bits with color 0D (and maybe color 1D too?).

--Bavi H (talk) 20:38, 25 June 2013 (MDT)