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MovieLabs Proposals: An Extended Dynamic Range EOTF Scott Miller, Dolby Labs.

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Presentation on theme: "MovieLabs Proposals: An Extended Dynamic Range EOTF Scott Miller, Dolby Labs."— Presentation transcript:

1 MovieLabs Proposals: An Extended Dynamic Range EOTF Scott Miller, Dolby Labs

2 MovieLabs Proposals: An Extended Dynamic Range EOTF What is an EOTF and why is it so important?  EOTF stands for Electro-Optical Transfer Function  It describes how to turn digital code words into visible light  The image on the reference display is what truly defines the signal  An artist makes creative decisions on what the content will look like while viewing a reference display  Could be sitting at a grading desk in a post production suite  Could be sitting in front of camera control units at a live production 2

3 MovieLabs Proposals: An Extended Dynamic Range EOTF Why is a new EOTF needed?  Ideally, the EOTF should be defined by the human visual response – but our current system is defined by this:  Current “Gamma” nonlinearity based on CRT physics  Finally standardized by ITU-R Rec. BT.1886  It is a sort of perceptual EOTF – but only at relatively low luminance levels and small dynamic ranges  But higher dynamic ranges are just around the corner 3

4 MovieLabs Proposals: An Extended Dynamic Range EOTF Building a new EOTF  Detailed user preference studies showed an absolute dynamic range of 0 to 10,000 cd/m 2 satisfied most viewers’ desires  Assume practical system will need to be a maximum of 12 bits  Due to current infrastructure and silicon constraints  Use human visual system to determine performance we need 4

5 MovieLabs Proposals: An Extended Dynamic Range EOTF Contrast Step Curves 5 PQ: Most efficient use of bits throughout entire range

6 MovieLabs Proposals: An Extended Dynamic Range EOTF Barten Contrast Sensitivity Function (CSF) 6

7 MovieLabs Proposals: An Extended Dynamic Range EOTF Perceptual Quantizer (PQ) EOTF 7

8 MovieLabs Proposals: An Extended Dynamic Range EOTF Doesn’t a 10,000 cd/m 2 system “waste” a lot of code words that we can’t use yet  The short answer is “no”  The logarithmic shape of PQ at the top end allows substantial gains in peak brightness without costing huge numbers of code words  Think of it as headroom for further expansion  PQ headroom from 5000 to 10,000 cd/m 2 = 7% of code space  Headroom above white in traditional SMPTE range gamma = 8% of code space  The midpoint of the code range for PQ represents about 93 cd/m 2  If we were using a traditional gamma function, headroom waste would be a huge problem 8

9 MovieLabs Proposals: An Extended Dynamic Range EOTF Gamma 2.4 Code Words 9

10 MovieLabs Proposals: An Extended Dynamic Range EOTF Perceptual Quantizer (PQ) Code Words 10

11 MovieLabs Proposals: An Extended Dynamic Range EOTF Conclusions  We need a standardized EOTF to define a new system for extended dynamic range  PQ is the most efficient way to encode extended dynamic range  Each code value corresponds to just under a perceptual step - less wasted codes  A 10,000 cd/m 2 system makes a lot of sense  The extra dynamic range is appreciated, and preferred by viewers  It gives the system headroom for display improvements in the future  No more bits are required compared to ~1000 cd/m 2 systems 11

12 MovieLabs Proposals: An Extended Dynamic Range EOTF Standardization  This EOTF has many potential use cases for baseband and compressed video  Similar to the many traditional uses of gamma  MovieLabs proposal: 10,000 cd/m 2 peak, XYZ color primaries, 12bit PQ  But the EOTF could also be used with other color spaces  SMPTE 10E Drafting Group working on perceptual EOTF  MPEG looking at signaling for perceptual EOTF in HEVC VUI metadata  SMPTE likely starting a High Dynamic Range / Wide Color Gamut study group in 10E as well 12


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