2015-12-02, 21:17
There seems to be much confusion on just what changing video levels do throughout the video chain from Kodi -> GPU -> TV and although the answers are available, they are buried deep in threads and spread throughout the forums. Since I'm very interested in this topic and have done quite a bit of research I plan to create a visual FAQ on just what happens when you change the video levels in your chain to either Limited or Full to hopefully provide a single place for people to really grok what is happening.
In this visual FAQ, I plan to show the intermediate changes in the chain from Kodi --> GPU --> TV for each combination of Limited & Full.
Before I create these pictures I wanted to clarify things first. Here is what I think happens, please correct me where I'm wrong:
I think I have the above just about right but I'm a bit fuzzy on what happens when you set your TV to either Limited or Full. Since the TV must convert to RGB Full at some point before displaying, what happens in the following scenarios?
Does setting Limited vs Full on your TV just tell the TV where it should expect Reference Black (and White) to be and set its pixel luminance accordingly?
That is to say:
Thank you for your help
In this visual FAQ, I plan to show the intermediate changes in the chain from Kodi --> GPU --> TV for each combination of Limited & Full.
Before I create these pictures I wanted to clarify things first. Here is what I think happens, please correct me where I'm wrong:
- Setting Kodi to 'Full' will expand YUV Lvl 16 to RGB Lvl 0 and expand YUV Lvl 234 to RGB Lvl 255 -- WtW and BtB will be clipped in this process
- Setting Kodi to 'Limited' will map YUV Lvl 16 to RGB Lvl 16 and map YUV Lvl 234 to RGB Lvl 234 -- BtB will be maintained at RGB levels 0-15 and WtW will be maintained at RGB levels 235-255; this is still a lossy conversion
- Setting GPU to 'Full' will pass through the video untouched as it comes from Kodi
- Setting GPU to 'Limited' will compress RGB Lvl 0 to RGB Lvl 16 and compress RGB Lvl 255 to RGB Lvl 234 -- What fills in RGB levels 0-15 & 235-255?
I think I have the above just about right but I'm a bit fuzzy on what happens when you set your TV to either Limited or Full. Since the TV must convert to RGB Full at some point before displaying, what happens in the following scenarios?
- GPU Reports RGB Limited in infoframes and TV set to Limited -- Does the TV map RGB Lvl 16/235 to RGB Lvl 0/255 and clip whatever was at Lvls 0-15 & 235-255?
- GPU Reports RGB Limited in infoframes but TV is set to Full -- What happens here?
- GPU Reports RGB Full in infoframes and TV is set to Full -- I'm fairly certain the TV doesn't do any remapping in this case and all is good
- GPU Reports RGB Full in infoframes and TV ignores it or is set to Limited -- What happens here?
Does setting Limited vs Full on your TV just tell the TV where it should expect Reference Black (and White) to be and set its pixel luminance accordingly?
That is to say:
- If TV is set to 'Limited', incoming content that contains RGB Levels 0-16 will cause those pixels to be fully off.
- If the TV is set to 'Full' then only incoming content that contains RGB Level 0 will cause those pixels to be fully off and anything above 0 will have those pixels be driven.
Thank you for your help