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High Dynamic Range

April. 2015Presented by Thuong Nguyentnguyen@humaxdigital.com

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SDR

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HDR

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Contents Introduction What is Dynamic Range Why High Dynamic Range is matter

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Improving Video Qual-ity

More pixels: SD – HD –UHD (4k, 8K)

Increase spatial resolution

HDTVUHDTV

SDTV

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Improving Video Qual-ity

Increase temporal resolution

More frame: 24 ~ 300 Fps (sport,

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Improving Video Qual-ity

More View (3D): Stereo, Multiple view, free view

Increase views – 3DTV

1 view 2 views M views

…

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Improving Video Qual-ity

More pixel’s info (Better pixel)

Higher contrast: SDR vs. HDR

Standard(SDR)

Enhanced(EDR)

High(HDR)

10 16 f-stops

n f-stops = a difference of 2n : 1 contrast ratio

Quantization bit: 8 – 10 – 12

strong contrast between the bright parts and the dark parts of an image

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Why? better-looking images/videos

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Problem of Dynamic Range

The Grandma Problem

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Long Exposure

10-6 106

10-6 106

Picture

High dynamic rangeReal world

0 to 255

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Short Exposure

10-6 106

10-6 106

Picture

High dynamic rangeReal world

0 to 255

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Problem Dynamic The real world is high dynamic range

A nit is a unit used to measure brightness

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High Dynamic Range Making the bright pixels on a TV as bright and vibrant

as possible while making the dark pixels as dark as possible.

Especially valuable for outdoor scenery and sharp contrast movie scenes.

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High Dynamic Range Need around 10.000 nits to satisfied 90% viewer at

ideal range

Current Color Space (Color Gamut) is not enough

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Moving to HDR UHD Alliance: with mission to create (Jan. 2015

at CES) New standard to support video technologies including 4K,

Higher resolution, high dynamic range, wider color gamut, and 3D audio

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Moving to HDR (Netflix) HDR is more important for video quality

than 4K

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Moving to HDR (Netflix) HDR is more important for video quality

than 4K “We kind of ran out of more pixels to add,” Neil Hunt,

Can notice HDR from any distance and screen size, at once

Resolution is only apparent when you are close

Dramatic better visual quality

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Moving to HDR Who interested?

TV manufacturers

…. ...TV manufactures mainlyTV manufacturers + Content creators

Optimistic future

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Moving to HDR 4K (UHD) will support HDR standard in the end of

2015. 4K + HDR (10/12bit) give less data overhead than 8K itself

(8bit)

MPEG Exploration: HDR and WCM content distribution

HDMI 2.0a (Apr. 2015): spec update fro HDR support in 4K

Ultra HD Blu-ray: will support HDR

Technicolor and Sinclair Demo HDR UHD Live Over-the-Air Broadcast (Apr. 9, 2015)

NAB Labs to Demo Super Hi-Vision, LDM, HDR HFR (NHK’s SHTV). (Apr. 11, 2015)

HDMI 2.0a: 18Gbps

SMPTE 2014: Doing HDR With HEVC

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HIGH DYNAMIC RANGEMore on

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HDR in Digital Photog-raphy

Dynamic range describes the ratio between the maxi-mum and minimum measurable light intensities (white and black, respectively)

Ratio between lightest and darkest regions (contrast ratio)

Never have true white or black Dynamic range’s concept depends on:

Capture device (camera, scanner)

Display devices(screen, printer)

Subject

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Influence of Light Light intensity as incident and reflected light

Real world is high dynamic range

Accurate measure luminance is critical for dynamic range

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Digital Cameras Light is measured at each pixel in a well (photosite)

Each photo’s size determine a digital camera dynamic range

Define darker and white level based on its capacity

(idea camera) Contrast ratio is dynamic range is generally higher for digital SLR cameras compared to compact cameras due to larger pixel sizes.

Maximum light intensity measurable ( at pixel

saturation)Minimum light intensity

measurable (above read-out noise)

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Comparison Dynamic range is commonly measured on a logarithmic

scale

Printed Media

f-stopsDensity

Scanner

Display devices

Scanners

Digital Camera

f-stopsDensity

Scanner

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The Human Eye Human eye uses the pupil to see darker or brighter im-

ages Turn smaller to limit coming light to see the brighter But cannot see darker & brighter region at same time it around 10 – 14 f-stops

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Bit depth & Dynamic Range

(bit per pixel)Quantifies how many unique colors are available

How many unique shades are available in grayscale im-age

Most digital cameras us a 10 – 14 bit A/D ~ 10-15 f-stops Higher precision A/D converter does not necessarily mean

greater dynamic range

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Wider Color Gamut Current color gamut is limited

Current HDTV (BT.709) – 1990 Created for CRT, and HDTV Around 100 nits. 8 bpp

Today we have better display technology: Plasma, LCD, OLED …

More Colors: REC. 2020 for UHDTV 10, 12 bpp.

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What the viewer gets? Distorts the image from what the director create

Content creator see 100 nits

Viewer see – 300-500 nits

Gamma correction

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What the viewer gets? Distorts the image from what the director create

Unpredictable distortion

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Color and Brightness

Luminance dynamic range for various technologies

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Dolby Vision & dual layer HDR

“dual-codec” technology that uses the HEVC 10-bit base layer plus an 8-bit AVC enhancement layer or two 8-bit AVC encodes.

Encoder

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Dolby Vision & dual layer HDR

Decoder

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HDR Related SEI in HEVC

HEVC version 2 include three SEI messages to HDR data

Chroma resampling filter hint: info for changing color space

Info: some transformation information to reduce artifact

Knee function information: info about transform one brightness or luminance dynamic range to another

Mastering display color volume: info on color primaries and luminance dynamic rage of the display tha was used to author the source

e.g: from REC 2020 (10-12bit) to REC 708 (8bit)

e.g. convert HDR for 500 nits to 120 nits

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HDR Develop ? Update gamma function: maps linear light to a spe-

cific code value for a display screen. Current system was originally designed to support CRT

display

Standardized signaling a television receiver for HDR’s contents

New metadata sets, how system delivery and response that.

Standardized HDR mapping …

How new HDR signals are carried Layered approach – which create different levels of video

quality Similar to SD/HD enable device?

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HDR Develop ? HEVC compatible to HDR contents (HEVC extension)

HDR – capable display devices with HEVC decoder

Workflow to create, encoded and distributable HDR video

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Conclusion High dynamic range is current trends in video technol-

ogy as well as industry (broadcasting operator, con-tent provider, TV manufactures)

Better visual perception with significant different to SDR Small bit overhead New HDR-enabled display device is coming

Very optimistic future – just around the corner

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References R. Diaz, An introduction to High dynamic range HDR and its

support within the H.265/HEVC Standard Extension, Dec. 2014.

Dolby Laboratories, Dolby vision white paper, 2014. http://www.cambridgeincolour.com/tutorials

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Appendix What’s remain

How to capture HDR? How to compress/encode HDR content? How to display HDR ? Dynamic range convert – Tone mapping ?

SDR to HDR HDR to SDR