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Journeyman III

YCC 4:2:2 output?

Would AMD support a non-standard way to make a real YCC 4:2:2 output possible?

Well, we know the YCC modes which you can select in CCC are fake. But I think they could be a very good basis to provide real YCC output.


The current YCC driver modes take the RGB color values from the RGB framebuffers, convert them into YCC format and output the YCC data through the HDMI output.

This means one thing is real: the actual data which goes through the HDMI cable is really YCC 4:4:4 or YCC 4:2:2 (according to the selection), so the hardware is capable of outputing both YCC formats.



My idea is to support either of these two solutions:

- Place a third "YCC 4:2:2 bypass"  mode next to the currently existing pixer formats which does the same thing as the current modes except it doesn't convert anything but bypasses the YCC 4:2:2 data as YCC 4:2:2 which is stored in the RGB 4:4:4 framebuffers.

- Place a third "Custom" mode  next to the currently existing pixer formats which is a simple RGB passthrough by default but can by freely redefined by user softwares (video players).


This way our custom video renderer could use the RGB framebuffers to store the YCC data and trigger this custom display mode to output real YCC data without going through the lossy conversions.

The chain would basically look like this:

Decoded video [NV12] -> chroma resize in one direction [YCC 4:2:0 -> YCC 4:2:2] -> YCC data in the RGB framebuffers -> YCC 4:2:2 output on the HDMI output.



The reason I want real YCC 4:2:2 output so badly because almost every HDTVs work with this format internally (except some models in PC and/or Game Mode but those modes usually have other drawbacks...)

(Yes, they all accept RGB 4:4:4 and YCC 4:4:4 but everything is always converted back to YCC 4:2:2 for internal processing...)


I believe this small thing would be very easy to provide by AMD while it could make a significant improvement in video quality for HDTV users who wish to watch their DVDs and Blu-Rays from their PCs.



AMD: Would it be theoretically possible?

(+ If you, as a user like the idea then post your opinion in this thread.)

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