Hardware Getting Full Range RGB From the Wii U in HDMI - An Accidental Discovery

IronCan

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The tl;dr is this. Converting the HDMI output into VGA then back to HDMI made it go from limited range RGB to full range. Yes, I know that sounds really stupid, hear me out, let me explain. I was comparing the video output of the vWii over HDMI with an original Wii running component through an Open Source Scan Converter (OSSC) (a scaler which can convert analog signals to HDMI and can integer scale resolutions 480p and below or even just output them as is) and noticed that the vWii was ever so slightly upscaled, even though both were outputting at 480p. I decided to run the Wii U through the OSSC by using a tendak HDMI to VGA converter to see if something was going on with the OSSC to cause this. In doing this I noticed that this had somehow made the output of the Wii U into full range RBG. So yeah, HDMI>VGA>HDMI = Limited Range>Full Range. For the record, the vWii was still slightly scaled, guess I'll keep the Wii around to satisfy my OCD for perfect picture quality.

I don't know why this works for certain, but I have a feeling it has to do with the way that the Wii U outputs its colours and the tendak converter being able to detect that it is in limited range and adjusting the VGA signal accordingly. Oddly enough, I tried this with a PS4 set to limited mode and it did not work, so I assume there must be something different about the colour space of the Wii U or something. I've heard that the Wii U outputs in in the YUV colour space, so maybe that's it? Could someone else confirm or deny?

Anyway, wild claims like this have to be backed up by some actual evidence, so here we go. Now, I'm using an ultrawide monitor with the ability to to picture by picture, so I have split the HDMI output of the Wii U so that one goes directly to the monitor, while the other goes to the HDMI to VGA converter, then through the OSSC, which is simply converting the image from VGA back into HDMI with no alterations, then to the other HDMI input of the monitor and setting them up with PBP to make the comparison much easier. The "Full range" output going through both converters is on the left, while the limited range straight from the Wii U is on the right. I chose a couple obvious pictures for comparisons (the all black of the resolution changing utility and the white of the mii maker showing off the very top and bottom ranges) and then the Bayonetta 2 screens because it was pretty visible to see there. Oddly enough stuff like smash bros and other nintendo titles don't seem to look all that different, probably made with the limited range in mind. Anyway. Pics!

20190509_214706.jpg 20190509_215006.jpg 20190509_215042.jpg 20190509_215057.jpg

I guess a few things I want to say/add as well.

First off, I know what the first question is going to be. How much lag? The answer is basically none. Neither of those converters have a frame buffer, so there's not much they can do that will actually add any lag. Don't believe me? I've got some evidence for that too. The video in the rar files is a video comparing the output of a ps2 displaying the lag test of the 240p test suite. For those that don't know, this is a tool used to test scalers and TVs on how well they perform for retro consoles. It outputs only in 15khz modes (so 240p, 480i and PAL equivalents). What is going on here is that this is a super slow motion video of two CRT monitors. The monitor on the right (which is tipped on to its side to play TATE games) is a 15khz CRT PVM style monitor. It is receiving the signal directly from the ps2. On the left is a PC style CRT monitor. It only accepts signals 30khz and above (ie 480p and higher). It is receiving a signal that has gone from the ps2, into the OSSC which has then converted it into HDMI and line doubled it from 240p to 480p (hence going from 15 to 31khz) and then converted back into VGA using the tendak converter. Yes, the conversion is done in the opposite order, but I think it's about as good a showing as I can give. Each time you see the picture drawn down the each of the screens, that is representative of one single frame. As you can see in the video, they are basically synced. If there is any lag it is on the scale of scanlines as opposed to frames, microseconds as opposed to milliseconds. Something that no human should be able to to notice.

Secondly, why would anyone do this? Doesn't the Wii U output full range over component? Well, this one is two fold. While most TVs are calibrated to display limited range, most computer monitors are calibrated to display full range. Displaying full range on a limited range TV will result in detail being lost in the darkest and brightest colours. Crushed blacks and so on. Displaying limited range on a full range display will result in the colours looking washed out, which was the case on my monitor. The output needs to match the style of display. This offers an option to those who use full range displays (like myself) as their primary displays for enjoying content like this. As for component, there are a few issues with the component on the Wii U. Firstly at 1080p it sucks. It's a blurry mess compared to HDMI. Maybe this has to do with the cables I am using, but it's not pretty. At lower resolutions it looks fine, but this still leaves another issue. It outputs in the Rec 709 colour space over component. This is in contrast to the wii and gamecube (and other older consoles from that generation) that output in the Rec 601 colour space over component. Now, the OSSC allows you to choose which colour space you're inputting over component, but I don't know enough about what TVs do. What I have seen is some threads that complain about the vwii looking slightly green over component. This is caused by a display interpreting the Rec 709 colour space as Rec 601 and as such displaying colours incorrectly. Using the HDMI neatly sidesteps both of these issues.

Finally the big one. The practicality of this. While the tendak converter is not too expensive, the OSSC is a relatively expensive scaler made for retro consoles, nobody would buy one just for this. And yeah, that's totally fair. I wanted to bring this up for two reasons. One - it may offer some insight in to how to make a mod for the Wii U that would allow it to output in full range. Secondly, I'm almost certain that there would be a cheaper VGA to HDMI converter that would work equally as well. The problem with most VGA to HDMI converters is that they sample 480p as 640x480 instead of 720x480 which is what the Wii U outputs over 480p. Additionally, I don't know enough about them to say how they sample 720p or 1080p, nor do I know enough to say which ones will do so with the minimal lag of the OSSC. I'm certain that one could be found that would do the job correctly, however and that would be far cheaper than the OSSC.

Anyway, that's enough of a ramble from me. I hope people have found this useful or if not, at least kind of interesting. Let me know what you think :):)
 

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miiuwiiu

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This is super long post. I am looking for an improvement in image quality. The Wii has the dual Wii mod. Why can’t the Wii I get this image quality improvement?
 
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