Quote:
Originally Posted by huhn
where did you toggle this? in madvr (devices -> monitor -> properties) madvr control + shift + alternative + i or in lav filter.
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Ιn ati CCC..pixel output format..
my question still remains..
assuming madvr is making the 16-235 to 0-255 luma expansion/conversion,should i be able to get the BTB and WTW information on my display?
according to this
http://sunmaiblog.wordpress.com/2010/10/06/calibrate-htpc-for-optimal-video-output/
""1. Luma resampling – Why WTW and BTB is important?
Luma resampling refers to expanding video level (16-235) to PC level (0-255), and as we can easily see that the procedure produces fractional numbers which even HDMI 1.4 can not carry. In order to send luma through HDMI, fractional numbers are rounded to integers.
Obviously there are several problems with such algorithm:
1) BTB and WTW is cut off after luma is expanded.
2) Banding is introduced (as the screenshot below shows). See the above example, the transition from 19-20 is mapped to 3-5. To reduce banding, we have to use a process called “dithering” which generates artificial pixels with luma 4 in between areas where luma is 3 and 5 in our example. Dithering is good in a way it reduces banding, but bad in a way it introduces artificial information which doesn’t exist in the original video.
3)Some graphics card later convert 0-255 back to 16-235
when using HDMI output which potentially causes even more information lost.
The luma information outside video range (0-16 referred to as BTB and 235-255 referred to as WTW) are important though we don’t normally see them in a movie. IMO they provide the following values:
It gives us the baseline when we calibration the brightness and contrast of our display.
It shows that the video luma is not cut off/expanded along the video pipeline.
Some movies have contents with luma value above 235, and as a result it’s recommended to reserve white up to 240 in order to see them.
Finally my suggestions are:
Avoid luma expansion/compression if possible. It’s perfect that our HTPC outputs 0-255 without expanding luma and our display cuts BTB and WTW.
If luma conversion cannot be avoided (most cases), make sure that dithering is enabled to reduce banding. We can use FFDshow with dithering enabled and HQ RGB conversion or MadVR to achieve this.""