<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - [GLK] no signal - with samsung 4k TV - HDMI UHD Color (ENABLED)" href="https://bugs.freedesktop.org/show_bug.cgi?id=110496#c35">Comment # 35</a> on <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - [GLK] no signal - with samsung 4k TV - HDMI UHD Color (ENABLED)" href="https://bugs.freedesktop.org/show_bug.cgi?id=110496">bug 110496</a> from <a class="email" href="mailto:teeedubb@gmail.com" title="teeedubb@gmail.com">teeedubb@gmail.com</a> <pre>Created <a href="attachment.cgi?id=145907" name="attach_145907" title="Chroma subsampling test in 4k60 non UHD Color mode">attachment 145907</a> <a href="attachment.cgi?id=145907&action=edit" title="Chroma subsampling test in 4k60 non UHD Color mode">[details]</a> Chroma subsampling test in 4k60 non UHD Color mode I haven't been able to find a method in software to check what level of chroma subsampling is being used with the 4k60 modeline in non UHD color mode, but I found a visual test that indicated that 4:4:4 is being used - I could read all the lines clearly from about6m away on a 65' TV. Closeup photo attached of the bottom two lines. So it seems that the GLK GPU doesnt agree with the UHD color mode EDID, but the modes that are exclusive to it can be forced via a custom modeline when not in UHD color mode. <a href="https://www.geeks3d.com/20141203/how-to-quickly-check-the-chroma-subsampling-used-with-your-4k-uhd-tv/">https://www.geeks3d.com/20141203/how-to-quickly-check-the-chroma-subsampling-used-with-your-4k-uhd-tv/</a> I didn't have any luck using modelines I found for a similar issue on askubuntu, so these may not work for other TVs, but here the three additional ones that are present in UHD color mode. xrandr --newmode "3840x2160_60.00" 594.000 3840 4016 4104 4400 2160 2168 2178 2250 +hsync +vsync xrandr --newmode "3840x2160_59.94" 593.407 3840 4016 4104 4400 2160 2168 2178 2250 +hsync +vsync xrandr --newmode "3840x2160_50.00" 594.000 3840 4896 4984 5280 2160 2168 2178 2250 +hsync +vsync</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are on the CC list for the bug.</li> </ul> </body> </html>