HDR and WCG Principles-Part 6

Dr. Mohieddin Moradi
mohieddinmoradi@gmail.com
Dream
Idea
Plan
Implementation
1

https://www.slideshare.net/mohieddin.moradi/presentations
2

− Elements of High-Quality Image Production
− CRT Gamma Characteristic
− Light Level Definitions & HVS Light Perception
− Dynamic Range Management in Camera
− An Introduction to HDR Technology
− Luminance and Contrast Masking and HVS Frequency Response
− SMPTE ST-2084: “Perceptual Quantizer”(PQ), PQ HDR-TV
− ARIB STB-B67 and ITU-R BT.2100, HLG HDR-TV
− Scene-Referred vs. Display-Referred and OOTF (Opto-Optical Transfer Function)
− Signal Range Selection for HLG and PQ (Narrow and Full Ranges)
− Conversion Between PQ and HLG
− HDR Static and Dynamic Metadata
− ST 2094, Dynamic Metadata for Color Volume Transforms (DMCVT)
Outline
3

− Different HDR Technologies
− Nominal Signal Levels for PQ and HLG Production
− Exposure and False Color Management in HDR
− Colour Bars For Use in the Production of HLG and PQ HDR Systems
− Wide Color Gamut (WCG) and Color Space Conversion
− Scene Light vs Display Light Conversions
− Direct Mapping in HDR/SDR Conversions
− Tone Mapping, Inverse Tone Mapping, Clipping and Color Volume Mapping
− HDR & SDR Mastering Approaches
− Color Representation for Chroma Sub-sampling
− UHD Phases and HDR Broadcasting, Encoding and Transmission HDR
− Different Log HDR-TV Standards
− Sony S-Log3 HDR Standard
− SR: Scene-referred and Super Reality (Scene Referred Live HDR Production) (SR Live Workflow )
Outline
4

Need for Tone Mapping (HDR ⇒ SDR) by Display Devices
4K HDR Monitor (PQ) HD SDR Monitor (PQ)
4K HDR Monitor (HLG) HD SDR Monitor (HLG) 6

Example: SDR Content into HDR without Proper Conversion
7
Very bright and over saturated
HDR into HDR Display
SDR into HDR Display – without conversion (LUT)
Correct

Example: HDR Content into SDR without Proper Conversion
8
Dim and undersaturated
SDR into SDR Display
HDR into SDR Display – without conversion (LUT)
Correct

Example: SDR Content into HDR without Proper Conversion
9
Very bright and over saturated
SDR into SDR Display
SDR into HDR Display – without conversion (LUT)
SDR is BT.709
constrained to 709 triangle
Consistent energy throughout waveform
Correct

Example: HDR Content into SDR without Proper Conversion
10
HDR into SDR Display – without conversion (LUT)
Dim and undersaturated
HDR is BT.2020
Outside of 709 triangle
Bulk of the energy below 75% highlights above 75%
Correct
HDR into HDR Display

Format Conversion in HDR Production, ITU-R Report BT.2408
Direct-mapping (mapping)
− Direct-mapping refers to the process of simply placing SDR content into an HDR signal container, at the
correct signal level.
• Typically 100% SDR > “HDR Reference White”, 75% HLG signal
Up-mapping
− Up-mapping is similar to direct mapping but SDR highlights given a small 'boost’ to better match the
appearance of a native HDR signals.
Down-mapping
− Down-mapping is the opposite of up-mapping. HDR signals converted to SDR by compressing the HDR
signal highlights.
Hard-clipping (less common)
− It can also be used for HDR to SDR conversion. Can deliver brighter SDR images and graphics, but any
highlights captured by HDR cameras are clipped.
• Down-mapping (tone-mapping) when converting to SDR, rather than hard clipping, will allow the SDR output to
benefit from the high dynamic range production by preserving some detail in the image highlights.
11

Clipping/Compressing Highlights and Shadows
Clipped highlights and shadows
• When converting from HDR to SDR there are
some circumstances when hard clipping
rather than tone mapping (akin to soft
clipping) may be more appropriate.
• With hard clipping all signals above a
threshold are clipped to that threshold.
• Hard clipping is useful when the signal from
an HDR camera is required to look similar to
the signal delivered by an SDR camera
operated without a “knee”.
12

Clipping/Compressing Highlights and Shadows
Compressed highlights and shadows
Compressed highlights and shadows
13

Clipping
− When converting signals from HDR to SDR, one approach is to hard clip the HDR signal so that signals
below a given threshold (e.g. HDR Reference White) are mapped into the SDR signal range, and signals
above the threshold are lost.
− This approach works well when the HDR signal is tightly controlled (for example by using the production
workflow described in further details for HLG production) to ensure that critically important image detail
lies below the clipping threshold.
− However, to allow the SDR signal to benefit from the HDR production workflow, down-mapping (tone-
mapping) is preferred.
14
Clipped Highlights and Shadows

Clipping
– Hard clipping is useful when the signal from an HDR camera is required to look similar to the signal
delivered by an SDR camera operated without a “knee”.
– With this method content undergoes no additional limiting/clipping in the event of multiple round-trip
conversions (i.e. PQ->HLG->PQ- >HLG) beyond the initial clipping.
15

Tone Mapping (TM) (Down-conversion): converting HDR content to an SDR signal range
• Limiting Luminance Range (Compression of the image dynamic range of content)
Inverse Tone Mapping (ITM) (Up-conversion): placing SDR content in an HDR signal with expanded
luminance range and thereby leverage the display capabilities to emulate an HDR look
• Expanding Luminance Range (Expansion of the image dynamic range of content.)
Tone Mapping and Inverse Tone Mapping
SDR Signal
(BT.709 or BT.2020)
SDR Display
(BT.709 or BT.2020)
HDR Signal
(BT.2020) SDR
HDR Display
(BT.2020)
SDR Signal
(BT.709 or BT.2020) HDR
HDR Signal
(BT.2020)
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– Since there is a great amount of legacy content which has been recorded, color graded and stored in SDR
formats, it needs to be converted for correct visualization on HDR displays.
– Inverse tone mapping (up-mapping) is intended to expand the content to use more of the available HDR
luminance range, and thereby leverage more of the display capabilities.
– In up-mapping SDR highlights is given a small 'boost’ to better match the appearance of a native HDR
signals.
– Up-mapping is intended to make content captured in SDR look more as if it had been captured in HDR.
Inverse Tone Mapping (Up-mapping)
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SDR Content
(BT.709 or BT.2020)
HDR Look
in HDR Program
(With Expanded
Luminance Range)
HDR BT.2020 Display
HDR Signal

− Inverse Tone Mapping (ITM) is a process performed on the original SDR source to create its HDR depiction, to
match real-world luminance values as faithfully as possible.
− However, accurate reconstruction of real-world luminances is an impossible task, because information is lost
due to
• data acquisition (sensor noise, dynamic range, saturation)
• data processing (quantization, conversion, clipping)
• artistic manipulations (color grading, applying artistic vision)
− One cannot “create” HDR from SDR (despite some claims) as the SDR content has no HDR information.
• Subtle differences in HDR greyscale are missing and the SDR color space is smaller
− However, one can “balance” SDR hue saturation and luma values, so that it looks correct on a HDR TV,
running in HDR mode.
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Inverse Tone Mapping (Up-mapping)

Features of the Methods Presented in Report ITU-R BT.2446-0 (2019)
– Tone mapping and inverse tone mapping are inherently methods that require trade-offs between, for
example, computational complexity, handling of visual artefacts such as over-exposed areas, as well as
the general mapping of luminance values, which may be different between live and graded content.
SDR to HDR conversion
– The desire in such cases would be to increase the dynamic range of the content to effectively enhance
its visual appearance.
– This requirement may be translated into several objectives that any SDR to HDR conversion process
should adhere to:
1) maintain details in the shadows
2) ensure that mid-tones are not unduly expanded
3) expand highlights up to the peak display luminance, insofar the quality of the content allows
4) ensure chromatic content is adjusted appropriately
5) maintain temporal stability
19

HDR to SDR conversion
– Tone mapping, i.e. the non-linear mapping between HDR to SDR content is a well-researched topic.
– There is a general notion that a reduction of the dynamic range needs to be governed by at least one
secondary goal, i.e. the visual quality needs to be preserved in some way.
– It has not been clear, however, what aspect(s) of visual quality need to be preserved.
– Different approaches to tone mapping have aimed to preserve for example brightness, local contrast or
visual appearance, each leading to imagery with a different look and feel.
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Different tone mapping algorithms tend to produce images with a different look and feel

21
ITMO:
Inverse tone mapping operator
TMO:
Tone mapping operator

22
ITMO:
Inverse tone mapping operator
TMO:
Tone mapping operator

23
Processing steps for inverse tone mapping method B
Simplified inverse tone mapping for HLG output

24
HDR to SDR tone-mapping method B
Block diagram of HDR to SDR conversion

Display-referred (DR) Inverse Tone Mapping (SDR ⇒ HDR)
– Display-referred (DR) preserves displayed colors – use for graded content and graphics.
• Display Referred or DR conversion is the technique that permits pictures displayed in their native display format to
have a similar image appearance when displayed on devices of a different format.
SDR Display
(Gamma on RGB, BT.709)
HLG Display
(Gamma on Y, BT.2020)
Display-referred (DR) Conversion
Images on their respective
displays have similar Look
SDR Source
(BT.709)
HDR Display Light
(HLG BT.2100)
HDRC-4000 HDR Processor
25

Scene-referred (SR) Inverse Tone Mapping for Cameras (SDR ⇒ HDR)
– Scene-referred (SR) preserves the colors of the camera sensor – use for matching the “look” of SDR
cameras with HDR cameras.
• For example, a Scene Referred or SR technique is usually applied when converting the output signal from an SDR
camera to match the color appearance of a native HDR camera output. SR conversion uses an internal “linear light”
processing stage to which the desired output OETF is applied.
Scene Light SDR Camera
CCU
Real-Time Shading
e.g., 1080P @50
(BT.709)
Scene-referred (SR) Conversion
e.g., 1080P @50
HLG (BT.2100)
SDR -> HDR
Display Light
≈
Same
Look
HDR Camera
Scene Light
Real-Time Shading
CCU
e.g., 1080P @50
HLG (BT.2100)
HDR
Display Light
26

Conversion Techniques for SDR <-> HDR
Display-referred (or Display Light) SDR to/from HDR conversion
• Graded content and graphics will appear in the new format as the colorist intended in the original
pictures
• Maintains “look” (i.e. saturation and tone) of content when converted to a new format and ensures that
both the SDR and HDR signals have the same look.
o Should not be used for matching cameras
Scene-referred (or Scene Light) SDR to/from HDR conversion
• Matches the “look” of SDR cameras to HDR cameras
o It should not be used for “graded or archival” SDR content -with HLG (𝒀𝜸) – as it will change the “look”,
and so the artistic intent
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• Different processes are needed for different applications
• Exercise caution in signal conversions to prevent Side Effects!

Natural and Traditional Look
− All TV Formats have their own “Look”. “ Look” implies a “Color Saturation and Image Tone”
− Natural and Traditional Look are terms introduced in standardization activities related to HDR operational
practices and that describe the picture appearance of a television signal process.
Natural Look:
− It is the most recent term and was used informally to describe the look of the HLG HDR format during the
creation of the ITU-R- BT.2100 standard.
• The HLG HDR format applies the gamma non-linearity to the luminance signal only and not to the
individual RGB components.
• This process creates a more subtle color presentation, resulting in a match of the color characteristics
of the native scene as imaged by the camera.
• For this reason, images created using HLG (BT.2100) are said to exhibit a “Natural Look”.
28

Natural and Traditional Look
− All TV Formats have their own “Look”. “ Look” implies a “Color Saturation and Image Tone”
− Natural and Traditional Look are terms introduced in standardization activities related to HDR operational
practices and that describe the picture appearance of a television signal process.
Traditional Look:
− With the Traditional Look the gamma curve is applied to the R, G and B, components individually which
results in more saturated color pictures.
• Since this process has been in use as the picture look of legacy, conventional and other television
production formats, including PQ, it has been called “Traditional Look”.
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− All TV Formats have their own “Look”.
“Look” implies a “Color Saturation and Image Tone”
− S -Log3 (Live), HLG (Live) and SDR have a similar “Traditional” look
• OOTF “gamma” is applied on R, G, B components independently.
• Increases saturation of displayed image
− HLG (per ITU-R BT.2100) has a “Natural” look
• OOTF “gamma” is applied to luminance component only
• Saturation of displayed images matches that of the scene
TV Formats and Their Picture Appearance - “Looks”
30

Conversion Techniques and Side Effects
31
Mixed production of Scene Referred and Display Referred conversions
Referring to the figure, it is
suggested that different
processes to be applied at
the various parts of the
program chain.

− This can be illustrated by examining the side effects in the two example scenarios described below:
− In the first example, up-converted signals from the SDR cameras created by “Scene Referred” conversion
are used in the HDR production layer.
• The output of the HLG HDR production master is then down-converted back to SDR for distribution,
using a Display Referred conversion technique.
− In the second example, graded SDR material (e.g. graphic elements) is inserted into the HDR production
layer by upconverting via a Display Referred process.
• An SDR signal is then created using a Scene Referred down-conversion, for contribution to other
broadcasters who wish to match this SDR feed to the look of their production cameras.
32
SDR ⇒ HLG (by DR) ⇒ SDR (by SR)
SDR ⇒ HLG (by SR) ⇒ SDR (by DR)

33
Examination of side effects by two scenarios
SDR ⇒HLG (by SR) ⇒SDR (by DR)

− The picture Side Effects are quite noticeable in both cases
− For the first scenario, skin and color tones exhibit a “natural look” as the Display Referred process imparts
the look of the HLG production master unto the SDR signal.
− For the second example, an oversaturation of skin and color tones can be observed on the SDR signal as
the result of concatenating the Display Referred and Scene Referred conversion processes.
− In both cases, the mixing of two different conversion techniques in one single production prevents the
proper reconstruction of an SDR signal which ideally should completely match the look of signals initially
created by the camera operators during the SDR shading process.
34

− The figure depicts simulated images to compare the original SDR picture vs SDR images created by the
round-trip process utilizing the conversion techniques of each scenario.
− Note that after “round-tripping” any SDR material included in the production using a display-light
conversion (e.g. graded inserts or graphics) will appear more saturated in the SDR scene-light output,
than in the original SDR version.
⇒ So, in general, a display-light conversion to SDR (HDR⇒SDR) on the final programme output is
preferred.
35
Reference SDR (BT. 709)
Less Saturated Over Saturated
SDR ⇒ HLG (by SR) ⇒ SDR (by DR) SDR ⇒ HLG (by DR) ⇒ SDR (by SR)

HLG
(DR)
HLG (Natural)
Original SDR
DR down mapping causes DESATURATION
Round Trip SDR (SR >DR)
SR
DR
36
Mixing of SR and DR in HDR Production: Practical Issues
SDR ⇒HLG (by SR) ⇒ SDR (by DR)

DR
SR
SDR Roundtrip
HLG (DR)
Original SDR
Using DR in SR system causes OVERSATURATION
Round Trip SDR (DR >SR)
Side effect
37
Mixing of SR and DR in HDR Production: Practical Issues

SDR Graphics,
Legacy:
(Graded, Archival)
Servers, Slomo Live
Feeds
SDR Cameras
HDR Cameras
HDR
HDR Scene-
referred
Conversion…
?
?
SDR Output Program
Display-referred
Conversion… ?
HDR -> SDR
Down-Conversion
HDR Conversion
for Distribution
Scene-referred
Conversion
Display-referred
Conversion
Scene-referred
Conversion… ?
HDR
HDR Production
(HLG BT.2100)
Video Production Switcher,
Editing, Conforming,
Special Effects
HDR Output Program
Different look to live
SDR camera sources
(HLG Natural Look)
More Saturated than
pre-graded SDR Sources
HLG
PQ
38
SDR⇒HLG(by SR) ⇒SDR (by DR)
Less Saturated than
SDR Camera Sources

Scene or Display Referred Conversion?
− Widespread confusion between industries and short hand nomenclature
• Mapping via Scene or Display light
• A Scene or a Display Referred system
• ACES definitions of a Scene or Display Referred input and output Images
39
Graphics or Test Patterns, SDR or HDR Display light
SDR to HDR Adverts Display light
HDR to SDR Program Display light
HDR to HDR Program Display light
Sony S-Log3 to SDR to match camera native SDR Scene light
To or from SDR BT.709 Cameras looking at the same Scene light
Conversion Content/intention Conversion Type : Via

Roundtrip Conversion (SDR <-> HDR <-> SDR)
– The conversion process from SDR to HDR, then come back to SDR is called “Round-trip”
White Level 100 nits
HDR
Black Level 0 nits
SDR
+5.2 dB -5.2 dB
Input Signal On Air
Skin Color (IRE70%)
50 nits
Caution:
• Applying different conversion methods
in a Round-trip process lowers the
luminance of the final SDR compared to
the original SDR image in case of same
SDR Gain setting.
• Applying same conversion method
between I/O makes it possible to
reproduce same luminance brightness
in the On-Air SDR images.
SDR
Display-referred
Conversion
Scene-referred
Conversion
Conversion (SDR-->HDR-->SDR)
Scene-referred Conversion
200 nits
203 nits
40

41
− The table contains the same information regarding
the Tone Mapping operation.
− It illustrates on which luminance 100% ‘SDR reference
white’ will be mapped onto an HDR reference
monitor with 1000 cd/m² in case of up-conversion
(see the left side in blue) and which luminance
displayed on an HDR reference monitor with 1000
cd/m² will be mapped to 100% ‘SDR reference white’
in case of down-conversion (see the right side in
green).
− Furthermore, this table contains the scene luminance
(i.e. with inverted OOTF) corresponding to the
respective display luminance as well.
* luminance [in cd/m²] on an HDR reference monitor with 1000 cd/m² (table
without clipping)
** luminance [in cd/m²] in the scene (inverting the OOTF)
*** luminance [in cd/m²] on an HDR reference monitor with 1000 cd/m² which will
be mapped to 100% SDR reference white
**** luminance [in cd/m²] in the scene (inverting the OOTF) which will be mapped
to 100% SDR reference white
LYNXTechnik AG
The Tone Mapping Operation of the Green Machine HDR STATIC Constellation

42
− In the case of “round-tripping” an SDR signal
(SDR>HDR>SDR), the Mapping Type “Tone Mapping
Scene Light” with default settings (Gain = 0 dB) is
used.
− During up-conversion, the 100% ‘SDR reference
white’ of this signal will be mapped to be displayed
with 287 cd/m² on an HDR reference monitor with
1000 cd/m² peak luminance. The scene luminance
corresponding to this display luminance is 415 cd/m².
− When down-converting this signal back to SDR, the
exact value of 287 cd/m² displayed on the HDR
reference monitor with 1000 cd/m² peak luminance
will be mapped back to the level of the initial 100%
‘SDR reference white’.
Tone Mapping Operation Example
* luminance [in cd/m²] on an HDR reference monitor with 1000 cd/m² (table
without clipping)
** luminance [in cd/m²] in the scene (inverting the OOTF)
*** luminance [in cd/m²] on an HDR reference monitor with 1000 cd/m² which will
be mapped to 100% SDR reference white
**** luminance [in cd/m²] in the scene (inverting the OOTF) which will be mapped
to 100% SDR reference white
LYNXTechnik AG

− Dynamic HDR enables a noticeable progression in overall video image quality from SDR to static HDR, and
now static HDR to dynamic HDR.
SDR Static HDR Dynamic HDR
Dynamic and Static Metadata in HDR
43

Static HDR uses a single image descriptor in metadata that is a compromise that applies to every scene and every frame of the whole movie.
Dynamic and Static Metadata in HDR
Static Metadata
Dynamic HDR ensures every moment of a video is displayed at its ideal values for depth, detail, brightness, contrast, and wider color gamuts
on a scene-by-scene or even a frame-by-frame basis.
Dynamic HDR image descriptor in metadata can be specific to each individual scene or even on a frame-by-frame basis.
Frame-by-frame Basis
Scene-by-scene Basis
Single Image Descriptor
44

HDR to SDR Conversion Approaches
– No Tone Mapping – UHD Alliance
– Static Tone Mapping (e.g. HDR10)
– Dynamic Tone Mapping
45
Fixed Grade at 1K nits in this case Monitor must be able to do a 1K grade
Fixed Grade at 1K nits in this case
Monitor will Scale the
input to its Nit range
Some code words can not viewed
Fixed Grade at 1K nits in this case Optimized for each scene or
frame in the contents
Levels based on Grade 1K, 2K, etc., so the monitor must matched the grade manually
Ex: frame-by-frame, or scene-by-scene basis (Varying the EETF based on statistics of the image)

No Tone Mapping – UHD Alliance
Fixed Grade at 1K nits in this case Monitor must be able to do a 1K grade
– Very much like HD Rec 709
– The Monitor has Fixed Levels
– Expects the content to be at the proper levels per scene as we do with Rec 709
– Levels based on Grade 1K, 2K, etc., so the monitor must matched the grade manually
46

Fixed Grade at 1K nits in this case Monitor will Scale the input to its Nit range
Some code words can not viewed
– Expects the content to be at the proper levels per scene as we do with Rec 709
– Metadata is sent to the Monitor that shows the Grade of the entire file
– If the file was a 1K Nit Grade but the Monitor can only do 700 Nits the monitor can adjust /Scale the input
Video to fit its Brightness range.
– HDR10 has static metadata [Reference display ST 2086 metadata+ MaxFALL+ MaxCLL]
Static Tone Mapping (e.g. HDR10)
47

Static Tone Mapping (e.g. HDR10)
− Optimized only for the brightest scene in the contents
− This avoids hard clipping of detail in the highlights
− It is not invariant under blind multiple round-trip conversions
Static Tone Mapping (HDR10)
200 1500
48

Dynamic Tone Mapping
− Color transforms optimized for each scene, and each Monitor
− ST 2094 Standardizes HDR color transform technologies from several companies
− Color and image information is carried in Metadata
− Select where and when to apply the Metadata information
49

− Optimized for each scene in the contents
− Ex: frame-by-frame, or scene-by-scene basis (Varying the EETF based on statistics of the image).
− This approach could survive multiple round-trip conversions
50

Static Conversions vs. Dynamic Conversion
Static conversions with a fixed LUT or a selectable LUT (the “look up table” that is the template for the
conversion)
– Static conversion offers always predictable results and allows controlling the offset between the SDR and
HDR depending on the users’ requirements.
– On the other hand there will be limitations especially during very challenging lighting conditions to get the
best SDR and HDR outputs at the same time.
Dynamic conversions that analyze the picture content and apply content-based settings.
– Dynamic conversion appears to offer a larger capability of processing inside the production chain,
although automatically adopting the look of the image might not be acceptable for all users or in all
cases.
– No doubt a variety of solutions are available today and even more will become available in the near
future covering a wider range of typical live applications.
51

Preserving SDR Image Quality with Dynamic Tone Mapping
− SDR footage inserted in HDR programs needs special handling when converting to SDR for preserving
original SDR imagery and preventing loss of image quality
− Dynamic Metadata provides needed information.
52

Consumer
Display
Color Volume Mapping
53

Typical UHDA HDR Display
e.x. OLED/LCD
Legacy SDR 709 Display
Future HDR Display
Display Color Volume
The 3D palette of all colors that can be
reproduced at all allowable intensities
Consumer
Display
54

HDR Image Color Volume
The pixels that comprise the HDR image change
location on a frame by frame basis
HDR Image
55

SDR Image
SDR Image Color Volume
56

SDR Display Color Volume
Consumer
57

− HDR Opening the Lid to “Pandora’s Pixel” Box
− HDR target displays have different Color Volumes (TV’s, Tablets, Mobile Phones, etc.)
− Use Color Volume Mapping to map content into the target display color volume
− Color Volume Mapping considers both
• Tone Mapping (Intensity)
• Gamut Mapping (Color)
Putting “Pandora’s Pixels” Back in the Box!
Note: Color Volume mapping is also
required for 4K Rec 2020 to HD Rec 709
conversion independent of HDR
Consumer
Typical UHDA HDR Display
e.g. OLED/LCD
Legacy SDR 709 Display
Future HDR Display
58

Static Content Mapping from HDR to SDR
Static Color Volume Mapping:
Container to Container
SDR Display Color
Volume (ITU-R BT.709)
HDR Mastering Display Color
Volume (SMPTE ST 2086)
Static Color Volume Mapping
Container to Container
59

Dynamic Content Mapping from HDR to SDR
Map Darks Up
Map Brights Down
HDR Content Dependent Color
Volume (SMPTE ST 2094-x)
Dynamic Color Volume Mapping
60

A Better Way
Map the Content based on real
time image content analysis
Region of the image
to prioritize
Putting the Pixels in the Box: Static Container Mapping of HDR to SDR
Min 0.041 𝐜𝐝/𝐦𝟐
Max 2775 𝐜𝐝/𝐦𝟐
Mean 21 𝐜𝐝/𝐦𝟐
61

A Better Way
Region of the image
to prioritize
Mean 238.7 𝐜𝐝/𝐦𝟐
62

Region of the image
to prioritize
A Better Way
Mean 1820.8 𝐜𝐝/𝐦𝟐
63

SMPTE
2084
PQ
Look
Up
Tables
Linear Ramp Test Signal BT.709
Look Up Table SMPTE 2084 1000nits
Reference White 100nits
Look Up Table SMPTE 2084 1000nits
Reference White 300nits
64
Using Look Up Tables (LUTs) In Post Production
2084 HDR (PQ) 0% 2 % 18% 90%
100
%
BT.709 100nits 0 9 41 95 100
HDR 1000nits 0 37 58 75 76
Camera-Side Conversion BT.709 (SDR) to PQ1K

HDR to SDR Color Volume Conversion
− It is expected that some colours that are present in the HDR colour volume when converted to SDR will be
outside of the ITU-R BT.709 volume Nominal Range but within the Preferred Range.
− This allows conversion processing to maintain the saturation and brightness of colours already within the
Nominal Range target colour volume.
Recall: EBU R103: Video Signal Tolerance in Digital Television Systems
66
System Bit Depth Range in Digital sample (Code) Values
Nominal Video Range Preferred Min./Max. Total Video Signal Range
8-bit 16-235 5-246 1-254
10-bit 64-940 20-984 4-1019
12-bit 256-3760 80-3936 16-4079
16-bit 4096-60160 1280-62976 256-65279

Preferred Min.
Preferred Max.
(Narrow
Range)
(White)
(Black)
(super-whites)
(sub-blacks)
Adjustments to ITU-R BT.709 Cameras
– In the conversion process from SDR BT.709 to HDR it may
be beneficial to include
• signals below black (sub-blacks)
• signals above the SDR nominal peak white (super-
whites)
– Such signals, which are often present in live SDR
television production, effectively increase the colour
gamut captured by the camera beyond the BT.709
colour primaries (Report ITU-R BT.2250).
– The permitted SDR signal ranges vary between
geographical regions.
– By way of an example, EBU R103 allows SDR signals to
span −5% to +105%.
67

Extending the BT.709 camera colour gamut
– The figure illustrates the maximum transmissible 𝒀′𝑪𝑹
′
𝑪𝑩
′
colour gamut.
– The contours are drawn for each normalized Y at an
interval of 0.1 on the CIE 1931 xy chromaticity
diagram.
– Negative values of R′, G′ and B′ widen the effective
colour primaries.
• The gamut is increased in the red and the blue,
and a smaller increase is also made in the green.
− Allowing the R′G′B′ signals to extend above 100%
increases the colour volume by allowing more
saturated colours at higher luminance.
The contours are drawn for each
normalized Y at an interval of 0.1 on
the CIE 1931 xy chromaticity diagram.
68

– The technique can be used to ensure a closer match
between BT.709 and BT.2100 cameras for colours that
are close to the BT.709 colour volume boundary.
– Where the SDR BT.709 camera output is only used for
shading and as the input to an SDR to HDR format
converter, the signal clippers can be fully relaxed to
maximise the captured colour volume.
• Not all format converters and production
infrastructure are capable of passing the sub-
black and super-white signals.
69
Extending the BT.709 camera colour gamut
The contours are drawn for each
normalized Y at an interval of 0.1 on
the CIE 1931 xy chromaticity diagram.

NBCU LUTs and Single Stream Recommendation
− NBCU, in collaboration with Cromorama, and building on ITU working group discussions for HDR
operational practices involving Dolby, BBC and Philips, has developed techniques to enable “single-
stream” production that feeds both UHD HDR and SDR transmission simultaneously.
− The NBCU LUTs developed for this workflow enable single-stream production whereby the HDR and SDR
products are consistent to the point where the benefits of HDR are realized making a unified production
possible.
− NBCU has a commitment to industry collaboration and would like to encourage consistent media
exchange, therefore we are willing to provide the NBCU LUTs freely. The NBCU LUTs are provided on an
“as is” basis with no warranties.
− The package of NBCU LUTs with additional documentation are available at the following link:
NBCU LUT Single-Stream Recommendations and LUT Package
70

71

72
Productions baseband
Productions File based

NBCU LUTs
− The focus of the entire conversion effort is to maintain the original artistic intent
such that the SDR derived from the NBCU LUT compared side-by-side is consistent
with the HDR until the point where the advantages of HDR are realized even with a
reduction of dynamic range in the converted SDR.
− The NBCU LUT7 converts HLG to PQ LUT using a mathematically transparent
equation which normalizes HLG at 1,000 NITS and preserving the original artistic
intent from the production to transmission.
74

Preserving Color Intent
75
HDR TO SDR - Original Saturation not preserved
HDR TO SDR – Color Clipping

Objective LUT Testing, Perceptual Objective Color Volume Metrics
− ITP Mimics perceptual aspects of the human
visual system
− “L”, “M”, “S” captures different wavelengths of
light which represent specific color ranges “I”
Captures Intensity (or amount of light).
76

Objective LUT Testing, Perceptual Objective Color Volume Metrics
77
Perceptual Objective Metrics
Absolute Objective Metrics
Normalized
Plotting
Space
Normalized
Plotting
Space

Preserving Color Intent, SDR to HLG Scene vs Display Light Conversion
78

Objective LUT Testing
79
Sarnoff Yellow Brick Road Pattern
This Plot Compares Sources vs Conversions
• Source 1 = HLG BT.2020 (BT.2020 colors)(BLUE)
• Source 2 = SDR BT.709 (BT.709 colors)(GREEN)
• Source 3 = HLG to SDR LUT3(RED)
𝑪𝑻𝑪𝑷 components from 𝑰𝑪𝑻𝑪𝑷allow us to visualize subtle hue shifts
𝑪𝑻
𝑪𝑷

SDR Converted to HDR with NBCU LUT
81
SDR Original HLG

82
SDR Original HLG

83
SDR Original HLG

HDR Converted to SDR with NBCU LUT
84
SDR
HLG Original

85
SDR

86
SDR
HLG Original

87
SDR
HLG Original

HDR & SDR Mastering
HDR
BT.2020
SDR
BT.709
89
The gain control (legacy “contrast” control)
The black level lift control (legacy “brightness” control)

16 bit
RAW material
Technical
grading
Creative
grading
HDR
master
SDR
master
10 bit
XAVC material
with S-log3
Technical
grading
Creative
grading
HDR
master
Post production
Acquisition Mastering
The HDR master can be used for
producing an HDR transmitted output
or HDR pre-recorded media.
SDR
master
Post-production consists of editing,
grading and conforming to create
both an SDR and HDR grade.
A digital cinematography camera
can record 16 bit RAW material and
10 bit XAVC material with S-log3.
This maintains the 14 stops (𝟏𝟎𝟓
) of
Dynamic Range with a Wide Color
Space.
HDR & SDR Mastering Example
RAW workflow
This provides post production with the greatest creative scope, but
requires huge amounts of data an powerful hardware.
S-Log3 & XAVC workflow
This provides post production with enough creative scope for most projects,
requires far less data than RAW and uses conventional post-production tools.
90

Which Grade First?
− HDR First
• Most exciting version first
• Best for real time workflows
• Less shading (HDR shader has much spare time)
− SDR First
• Do the money-making version first
• Not 10 bits SDR distribution images
(Normally 8 bits, so should be increased to 10 bits)
− Independently graded from master media
• Very expensive (double efforts)
• Highest quality for both version
• Some colorists find it difficult to grade both HDR and SDR.
91

Viewing Experience Compromise For SDR Audiences in HDR Grading First
92
HLG HDR (SDR Focused Production)
HLG look
SDR with
HLG look
− The most broadcasters are aiming to produce in HDR and
“down-convert” to SDR for their SDR networks.
− If the SDR production must not be compromised, both HDR and
SDR cameras should be shaded using an SDR monitor fed via a
down-mapper.
− In that case, for final SDR distribution, a display-light HDR to SDR
conversion is probably most suitable, as it maintains the “look”
of the HDR signal after conversion.
− The SDR that is derived from the HDR production should closely
resemble the SDR that was used to shade the cameras.
− But a display-light conversion, which preserves the “look” of the
HDR output in the SDR, will produce content with a very different
“look” to the SDR camera output that was used for shading.
⇒ That difference may compromise the viewing experience
for SDR audiences.

Simplified HDR camera architecture
SDR Output Created for HDR by Reversing Camera Signal Flows
93
− In this example, a gain offset of ~4.2 (12.5 dB) will ensure that a camera adjusted to deliver a typical 100%
SDR signal for a 90% reflectance chart will deliver HLG HDR signals in accordance with ITU-R BT.2408 – HDR
Reference White at 75% HLG.
A gain offset of ~4.2 (12.5 dB)

SDR Output Created for HDR by Reversing Camera Signal Flows
94
− By changing the direction of the signal flows in the camera block diagram, it is easy to see how a scene-
light HDR to SDR format conversion will allow the HDR production to be converted to SDR that closely
matches the SDR camera output.
Scene-light HDR to SDR conversion
The HDR to SDR conversion could apply more sophisticated tone-mapping from HDR to SDR and more sophisticated color
management to minimize hue distortions. But the diagrams neatly illustrate the principles of scene-light conversion, and
hard-clipping of the 𝑹𝒔𝑮𝒔𝑩𝒔 SDR signals to fit within the BT.709 color volume is actually quite common in cameras.
The non-linear R'G'B' HLG signal is
passed through an HLG inverse OETF to
recreate the linear scene-light signal
produced by the camera sensor.
The scene-light signal is then
passed through the same SDR
processing chain found in the
camera – a scaling of ~4.2.
Scene-light conversion preserves camera
sensor colours - use for matching cameras
-0.05-1.05
0-1.09

A Full Parallel HDR and SDR Workflow
− A full parallel HDR and SDR workflow is the easiest way to produce both HDR and SDR at the same time,
from a single camera system through the full production chain.
− In a full parallel scenario, the camera delivers two simultaneous signals, one HDR and one SDR.
− For the very best HDR images BT.2408 recommends that cameras are shaded using their HDR output, with
the SDR output following.
95

− Although there is only one iris adjustment for the camera, the operator (cameraman, or VE: video
engineer) must adjusts the iris so that both the SDR and HDR have a pleasing image (based on the
experience and judgment of the VE).
− The VE must confirm the images for both HDR and SDR, such that the HDR high brightness characteristics
being touted for their viewer impact are appearing in frame (above 100% or the SDR range) while being
able to express that image properly in SDR with all content 100% or less.
− It is necessary to confirm this has been achieved.
96

− A camera capable of performing the SDR / HDR hybrid operation must provide functionality capable of
achieving the above described iris adjustment without hesitation by the operator.
− For this purpose, it is necessary to develop functionality to define and manipulate the relationship between
the HDR signal and the SDR signal output from the camera.
97

− Since the characteristic curves of SDR and HDR (HLG) are strictly defined, one might assume that it is only
necessary to issue signals along the proscribed curves, but with a great deal of scene compositions if you
do this the HDR compatible monitor will appear darker than the SDR compatible monitor.
− In addition, although the signal standard in SDR-TV assumes 100% maximum brightness 100 nits, in practice
modern current displays tend to be adjusted to the full brightness capability, so the SDR monitor will be
even brighter than the HDR compatible monitor, causing a kind of Inversion phenomenon.
98
Figure shows the standard
gamma characteristics of
SDR (BT.709) in blue, and
HDR (HLG) in solid red
(camera side).
Although 100% of SDR peak scene
brightness is 50% of HDR-HLG, it is
necessary to be aware that this graph
shows the camera side conversion curve -
optical electrical transfer function (OETF).

99
Optical-optical Transfer Function (OOTF)
− When a white object is exposed with a level of 100% of the scene light, a properly adjusted SDR-TV follows
the standard when displaying this as 100 nits, and HDR-TV can also show an object outside of the SDR TV
range up to 1200% (12x) of the maximum 100% brightness as 1000 nits; but when exposing in this way the
original SDR 100% white object will only display as 50 nits.
Level of white object SDR-TV 100 nits on screen
Level of white object HDR - TV 50 nits on screen (half
brightness of SDR - TV)
Thus at the normal brightness levels (presumably most
of the content), the SDR-TV will be brighter (blue line).

− Furthermore, in the current consumer SDR-TV, since the highest brightness of the screen tends to be set
above 100nits, the SDR-TV looks even brighter, which means that for many scenes HDR will simply not match.
− In order to match the HDR and SDR images for content within the SDR range, a gain difference can be
applied to the HDR and SDR signals such that they converge in the lower exposures.
− Once this HDR/SDR difference or offset has been set to specific scene conditions it then becomes possible to
set iris levels for both HDR and SDR by simply setting the iris to the proper SDR level relying on years of
experience, and best practices.
− With this technique it is also possible to match the image of the conventional SDR image for darker areas
while still using the high dynamic range of HDR effectively in the HLG image.
100

− Although it is necessary to set the optimum value
for the gain difference between the HDR video and
the SDR video by observation, it is assumed that it
will be a fixed value for a given condition.
− A study of the mapping method of SDR signal to
HDR signal for SDR/ HDR simultaneous output
operation has revealed an effective offset level
corresponding to 100% SDR signal to 75% HLG
signal (equivalent to 200 cd / m 2 at peak 1000
cd/m² : Pink line) and another mode (green line)
corresponding to a 100% SDR signal corresponding
to a 63% HLG signal (corresponding to 100 cd/m²
at a peak of 1,000 cd/m²) has been studied.
101

Gain (Offset) Control
− For a case where the screen is bright and there are many high luminance areas/objects (bright objects with
a wide dynamic range), adjusting the gain difference by about -10 dB between SDR and HDR thereby
setting the 75% point of HDR to the 100% level in SDR, matching SDR and HDR images become manageable.
With a narrow dynamic range image, setting a reduced gain difference offset becomes appropriate.
102
Specific Control of Gain (Offset) and Knee to Establish SDR/HDR Image Adjustment
− Thus setting the proper gain difference between SDR and
HDR according to the scene brings out both characteristics
and it becomes a practical solution to make HDR video by
setting proper SDR video exposure.
− It is not however recommended to dynamically change this
offset gain during shooting. It is sensible to follow set the
offset according to the larger contrast conditions which will
likely not change for a given camera position. A consensus
is building among HDR production teams accumulating
experience of simultaneous shooting of HDR & SDR.

HDR Knee control
− In SDR image capture it has been possible to compress more dynamic range into the legal SDR signal
contrast by utilizing the knee circuit.
− The knee takes much of the out-of-range bright areas the camera imager captures and compresses them
into the top ~80%- 100% of the SDR characteristic; engineers will adjust the knee point and slope to control
these highlight areas.
103
− When the offset between HDR and SDR is reduced to
match pictures there is now some unused dynamic
range in the highlights of the HLG image that can be
utilized for an HDR knee adjustment.
Specific Control of Gain (Offset) and Knee to Establish SDR/HDR Image Adjustment

104
VE Operation During Simultaneous SDR / HDR Broadcasting - Summary
1. It is necessary to consider image output
and exposure level suitable for both formats
3. The gain difference between the HDR video and the SDR
video is realized in the downconverter section of the studio
camera’s CCU. In addition, conversion of characteristic
curve, color gamut and knee processing are also
performed here.
2. To achieve matching exposure levels a predetermined gain
difference/offset can be pre-set between the HDR and SDR signals
(based on scene contrast levels) and then the video engineer or
shader can adjust the iris level based only on the SDR video.
In this way images are created that effectively utilize the high
dynamic range of HDR while attaining correct SDR video as before
and operation is transparent to the shader utilizing existing qc
monitors and wave form monitors.
4. The same offset value is set for the newly
developed HDR-SDR “downconverter” installed at
the switcher output as the offset setting for the
“downconverter” in the CCU.
This makes it possible to have the HD output from
the camera match the main line HD output from
the final down converter, so accurate adjustments
can be made at the camera side.

Live Output Signal Adjustment
− SDR studio cameras are equipped with various image manipulation
functions such as black gamma, knee adjustment, color matrix
adjustment, and so on to manage difficult scene content and provide
more tools to deliver a desired look.
− In HDR shooting, the same image manipulation functions are
expected.
− The HDR compatible studio cameras have introduced black gamma,
knee adjustment, color matrix and similar image quality adjustment
functions popular in SDR to the HDR image, and therefore can create
an appropriate picture according to the scene content and the
sensibilities of the producer.
− With these adjustment capabilities confirmation of this picture quality is
critical, so we think that it is important to output directly viewable HDR
from the camera with HLG so it can be viewed as it adjusted.
105

− In this simultaneous HDR and SDR production workflow
• the camera lens iris is set to HDR output to the required level
• the SDR gain is used to control the SDR output to the required level
− As long as the scene lighting does not change significantly, the lens iris will not need to be changed and a
moderate variation of the lighting condition will be well inside the headroom of the HDR output.
− In comparison, SDR does not offer this additional headroom, so a much more precise adaptation of the
sensitivity will be required.
106

− Challenges in this workflow include the simultaneous shading of HDR (which requires less work due to the
higher dynamic range) and SDR signals (which requires more work due to the limited dynamic range) as
well as the handling of both signals separately through the full production chain.
− This translates into a more complex and expensive workflow which might be accepted for certain
applications and/or for an intermediate period of time, but might not be acceptable in the long term.
107

2018 Trials Utilized Parallel HDR/SDR Production Workflows
108
Parallel workflows no longer
recommended
• Costly
• Complex
• HDR camera outputs do not always
track SDR camera outputs
− Many cameras used in live HDR TV production offer simultaneous HDR and SDR outputs.
− They can usually be configured to allow the camera shader to monitor one format and allow the other
output to follow, with a fixed gain (or exposure) offset.
− Both camera outputs can be used to feed parallel HDR and SDR production chains, often with the HDR
production switcher slaved to the SDR production switcher.

Native HDR from Camera and HDR-to-SDR Conversion
− An alternative to the full parallel HDR/SDR workflow is to use only native HDR signals from the camera and
then perform an HDR-to-SDR conversion somewhere during the production.
− While this simplifies the workflow and reduces the amount of resources required, in contrast to the parallel
HDR/SDR workflow, there is no separate control for the SDR and HDR outputs, and the SDR gain cannot be
independently controlled from the HDR signal.
− As a result, the success depends on the quality of the HDR-to-SDR conversion under all types of lighting
conditions.
109

Optimized HDR/SDR Compatible Workflow for Live Broadcast
− For the best results under the widest range of production environments, Grass Valley recommends a native
HDR workflow where SDR is derived by conversion.
− For the very best HDR images BT.2408 recommends that cameras are shaded using their HDR output, with
the SDR output following (dynamic down mapping is required).
− Which signal to be used for camera shading depends on the type of conversion.
110

Operational aspects: Before preparing an HDR production, a few things need to be cleared up front:
− Which version of HDR is requested, HLG or PQ?
• If PQ will be used, what is the clip level, 500 – 10,000 Nits? Typically it’s set to 10,000 Nits.
• If HLG will be used, what is the SDR set point, 50% or 75%? After latest changes to the recommendations, it’s typically 75%.
− What color gamut is requested, BT.709 or BT.2020? Typically it’s BT.2020 for HDR productions.
− What luminance and color difference signal representation is requested? Typically YCbCr is used.
− What code value range is requested, narrow or full? For most live applications, it’s narrow.
− What kind of SDR downmapping is requested, static or dynamic? Depending on the downmapping, shading
needs to be done on HDR or SDR.
111

Live HDR-TV a Huge Challenge
Wide Range of Cameras and Sources and Delivery to
Variety of Platforms
− 40 cameras common for major sporting events
− Includes wide range of specialist cameras
• Net cams, Spyder cams, Slo-mo cams, Robo
cams, Stump cams
− Many specialist cameras SDR only for years to come
− Intermixing of SDR and WCG HDR cameras
inevitable during transition
− Excellent colour matching between SDR BT.709 and
WCG HDR cameras essential
− Single HDR WCG workflow, delivering to both HDR
and SDR platforms essential, to manage costs
© Camera Corps
© Spydercam
© Camera Corps
https://www.bbc.co.uk/rd/projects/high-dynamic-range
112

113
Transitioning from SDR BT.709 to HDR BT.2100 Production
Meet the Shaders

114
SHADER, SDR
SHADER, HDR

115
Display-referred and Scene-referred Conversation
• Display Light Mapping tends to preserve the look created by the transfer characteristic used by the display
(plus artistic intent)
• Scene Light Mapping tends to represent the look of the signal being converted to (i.e. look of target format).

Scene Light vs Display Light Mapping
116
– In the following example of SDR-to-HDR up-conversion from SDR (Gamma BT.709) to PQ-BT2100
• Display Light Mapping would result in the “traditional” BT.709 look (i.e. to preserve the look created by
the transfer characteristic used by the display (plus artistic intent))
• Scene Light Mapping would lead to a PQ look (i.e. look of target format).
Display Light Mapping
tends to preserve the look
created by the transfer
characteristic used by the
display (plus artistic intent)
“Traditional” BT.709 Look
PQ Look
Scene Light Mapping tends
to represent the look of the
signal being converted to.

– Display-referred (DR) preserves displayed colors – use for graded content and graphics.
• Display Referred or DR conversion is the technique that permits pictures displayed in their native display format to
have a similar image appearance when displayed on devices of a different format.
SDR Display
(Gamma on RGB, BT.709)
HLG Display
(Gamma on Y, BT.2020)
Images on their respective
displays have similar Look
SDR Source
(BT.709)
HDR Display Light
(HLG BT.2100)
117

– Scene-referred (SR) preserves the colors of the camera sensor – use for matching the “look” of SDR
cameras with HDR cameras and vice versa.
• For example, a Scene Referred or SR technique is usually applied when converting the output signal from an SDR
camera to match the color appearance of a native HDR camera output. SR conversion uses an internal “linear light”
processing stage to which the desired output OETF is applied.
Scene Light SDR Camera
CCU
Real-Time Shading
e.g., 1080P @50
(BT.709)
e.g., 1080P @50
HLG (BT.2100)
SDR -> HDR
Display Light
≈
Same
Look
HDR Camera
Scene Light
Real-Time Shading
CCU
e.g., 1080P @50
HLG (BT.2100)
HDR
Display Light
118

– During the transition from SDR to HDR production:
– Native HDR production architectures highlighting either HDR or SDR focussed production.
– Over time, as audiences adopt HDR television displays designed for BT.2100 signals, production
architectures may be expected to shift from focussing on delivering primarily for SDR, to delivering
primarily for HDR.
The majority of viewers will be watching in SDR, so it is important that the SDR
production is not significantly compromised by the introduction of HDR.
119
– Note that in both production architectures the eye may
adapt to the brighter HDR monitor, affecting the
appearance of signals on the dimmer SDR screen.
⇒ So, the HDR and SDR screens should be physically
separated for critical assessment of the SDR signal.
HDR Focussed Production

Fig. 1
HDR production with SDR derived by down-mapping
120
HDR Focussed Production (HDR Production with SDR Derived by Tone Mapping)

− For the very best HDR images BT.2408 recommends
that cameras are shaded using their HDR output, with
the SDR output following.
− SDR graphics should be directly mapped into the HDR
signal at the “Graphics White” signal level specified
(75% HLG or 58% PQ)
• to avoid them appearing too bright
• and thus making the underlying (most
important) video appear dull in comparison.
121

1. Where the desire is to maintain the colour branding
of the SDR graphics, a display-light mapping should
be used, “as that should ensure the same hue and
saturation of graphics in both HDR and SDR” .
2. Where the desire is to match signage within the
captured scene (in-vision signage; e.g. a score
board at a sporting event), a scene-light mapping is
usually preferred.
3. Work is currently underway to determine the best
practice for HDR key signals (CG).
⇒ In the interim, using an SDR key signal directly
has been found to deliver satisfactory results.
122

− In this HDR focused production, BT.709 cameras may
be included in the production by using the “scene-
referred” SDR direct mapping technique.
− To ensure that the SDR “look” is maintained, the
“display-referred” SDR mapping should be used.
− To ensure a closer match between HDR and SDR
cameras, up-mapping (which expands highlights in
the SDR signal) is preferred (scene-light up-
mapping).
• As highlights are often heavily clipped by SDR
cameras, only a small amount of highlight
expansion may be possible.
• Further colour match improvements can be
made by relaxing the SDR signal clippers. 123

Recall: There are two levels of dynamic HDR conversion:
− level 1: dynamic per frame: every frame is analyzed in order to find the best mapping function (+ temporal
filtering)
− level 2: dynamic within a frame: every part of a frame is analyzed in order to find the best mapping
function (+ temporal and spatial filtering)
124
Dynamic Within A Frame Or Dynamic Sectional
Dynamic Per Frame Or Dynamic Global - Examples

− For optimum quality HDR pictures, both HDR and SDR
cameras should be shaded using an HDR monitor.
− Nominal signal levels for shading are given in the
table.
− As the exposure latitude of HDR images is far greater
than SDR, a dynamic HDR to SDR converter may be
required to deliver a satisfactory SDR output.
− The SDR output is derived via Display-referred tone
mapping. A display-light conversion ensures that
both the SDR and HDR signals have the same look.
Reflectance Object or
Reference
(Luminance Factor, %)
Nominal Luminance
Value
(PQ & HLG)
[Display Peak
Luminance, 1000 nit]
Nominal
Signal
Level (%)
PQ
Nominal
Signal
Level (%)
HLG
Grey Card (18% Reflectance) 26 nit 38 38
Greyscale Chart Max (83%
Reflectance)
162 nit 56 71
Reflectance)
179 nit 57 73
Reference Level:
HDR Reference White (100%
Reflectance) also Diffuse White
and Graphics White
203 nit 58 75
125

− A dynamic converter is designed to optimize the
HDR to SDR tone mapping curve for any scene,
thereby accommodating a wider range of
exposures than might be possible with a fixed (or
static) tone mapping curve.
− A dynamic down converter may sometimes provide
a more satisfactory SDR output than a static tone
mapper but attention should be paid to graphics
which may need to be inserted after dynamic
down-mapping, to ensure a fixed signal level.
Reference
Nominal Luminance
Value
(PQ & HLG)
[Display Peak
Nominal
Signal
Level (%)
PQ
Nominal
Signal
Level (%)
HLG
Reflectance)
162 nit 56 71
Reflectance)
179 nit 57 73
Reference Level:
and Graphics White
203 nit 58 75
126

− A scene-light HDR to SDR conversion may also be
included where it is important to colour match the
converted PQ or HLG output to downstream SDR
BT.709 cameras.
− However, consideration should be given to
potential changes in colour saturation of graded
content (see the displayed “look” of content
following format conversion in next slides).
− Ultimately, the choice of HDR to SDR down-
mapping depends on the application.
− To ensure the highest quality SDR output, cameras
are checked using an SDR monitor fed via identical
HDR to SDR converters to those used on the main
programme output.
Scene-Light
Down-Mapping
HDR BT.2100 to
SDR BT.709
127
Scene-Light
Down-Mapping
HDR BT.2100 to
SDR BT.709

− Where SDR content is mapped into an HDR container and the HDR signal then down-converted to feed an
SDR service (SDR-HDR-SDR “round-tripping”), the mapped SDR content may appear darker on the SDR
service than if it had been broadcast directly.
128
HLG(DR)
HLG (Natural)
Original SDR
DR down mapping causes DESATURATION
Round Trip SDR (SR >DR)
SR
DR
− Differences in black level may be more visible
in the down-converted SDR signal than in the
HDR signal, as glare from bright highlights in
the HDR image can mask detail in the
shadows.
Glare from bright highlights in HDR Signal

− Differences in black level may be more visible in
the down-converted SDR signal than in the HDR
signal, as glare from bright highlights in the HDR
image can mask detail in the shadows.
− To help ensure a consistent black level in the HDR
and down-converted SDR signals, a dedicated
waveform monitor displaying the lower portion of
the signal range is recommended. Reflectance Object or
Reference
Nominal Luminance
Value
(PQ & HLG)
[Display Peak
Nominal
Signal
Level (%)
PQ
Nominal
Signal
Level (%)
HLG
Reflectance)
162 nit 56 71
Reflectance)
179 nit 57 73
Reference Level:
and Graphics White
203 nit 58 75
129

HDR Focussed Production Notes, Summary
− SDR graphics should be directly mapped into the HDR signal at the “Graphics White” signal level specified (75% HLG or
58% PQ) to avoid them appearing too bright, and thus making the underlying video appear dull in comparison.
• Where the desire is to maintain the colour branding of the SDR graphics, a display-light mapping should be used.
• Where the desire is to match signage within the captured scene (in-vision signage; e.g. a score board at a sporting
event), a scene-light mapping is usually preferred.
− The BT.709 cameras may be included in the production by using the “scene-referred” SDR direct mapping technique
(SDR⇒HDR). To ensure that the SDR “look” is maintained, the “display-referred” SDR mapping should be used (SDR⇒HDR).
A display-light conversion ensures that both the SDR and HDR signals have the same look. To ensure a closer match
between HDR and SDR cameras, scene-light up-mapping (which expands highlights in the SDR signal) is preferred.
− The SDR output in HDR focused production is derived via Display-referred tone mapping. A display-light conversion
ensures that both the SDR and HDR signals have the same look.
• A dynamic down converter may sometimes provide a more satisfactory SDR output than a static tone mapper but
attention should be paid to graphics which may need to be inserted after dynamic down-mapping, to ensure a fixed
signal level.
− A scene-light HDR to SDR conversion may also be included where it is important to colour match the converted PQ or
HLG output to downstream SDR BT.709 cameras. 130

HLG production: A trial carried out by the BBC
Fig. 2
131
SDR Focussed Production (HDR Production with Camera Shading in SDR)

FS-HDR, Real Time HDR/WCG Conversion
132

SDR Focussed Production
− If the SDR production must not be compromised,
both HDR and SDR cameras should be shaded
using an SDR monitor fed via a down-mapper.
− Whilst the HDR signals may not always exploit
the full potential of the HDR production formats,
the HDR pictures can still show significant
improvement over SDR.
− We will discus PQ and HLG production.
Reference
Nominal Luminance
Value
(PQ & HLG)
[Display Peak
Nominal
Signal
Level (%)
PQ
Nominal
Signal
Level (%)
HLG
Reflectance)
162 nit 56 71
Reflectance)
179 nit 57 73
Reference Level:
and Graphics White
203 nit 58 75
133

− SDR focussed HLG and PQ production can use the
same workflow as shown in figure 1 except:
• The SDR check monitor is now the shading monitor
• The HDR shading monitor is now the check monitor.
− A trial HLG production carried out by the BBC is
illustrated in simplified form in figure 2.
− An additional scene-light PQ to SDR BT.709
conversion may also be included for colour
matching with downstream SDR BT.709 cameras.
Reference
Nominal Luminance
Value
(PQ & HLG)
[Display Peak
Nominal
Signal
Level (%)
PQ
Nominal
Signal
Level (%)
HLG
Reflectance)
162 nit 56 71
Reflectance)
179 nit 57 73
Reference Level:
and Graphics White
203 nit 58 75
SDR Focussed Production
134

− The “Clean or World Feed” SDR signal may be derived
from the HDR signal using a scene-light conversion, to
match other broadcasters’ SDR cameras that may also
be present at the venue.
− For any SDR output containing graphics (e.g. for the
broadcaster’s own SDR service) a display-light
conversion is recommended, as that should ensure the
same hue and saturation of graphics in both HDR and
SDR outputs.
− Note: Down-mapping (tone-mapping) when
converting to SDR, rather than hard clipping, will allow
the SDR output to benefit from the high dynamic range
production by preserving some detail in the image
highlights.
SDR Focussed Production, HLG production
135

− The SDR graded content should be inserted into the
programme using display-light direct mapping or
up-mapping, to preserve its original “look” and the
artistic intent.
− The SDR graphics should be display-light directly
mapped into the HDR format.
− Note that after “round-tripping” any SDR material
included in the production using a display-light
conversion (e.g. graded inserts or graphics) will
appear more saturated in the SDR scene-light
output, than in the original SDR version.
136
⇒ So, in general, a display-light conversion to
SDR on the final programme output is preferred.
More
Saturated

− During the transition to full HDR production, not only
will it be common to include SDR BT.709 cameras
within a production, but locally recorded action
replays and programme inserts may also be limited to
SDR BT.709.
− The scene-light up-mapping SDR BT.709 to HDR BT.2020
can be used for this part.
C
V
CV
C
V
HDR cameras
HDR Signal
137

− Additionally, a host broadcaster may be required to
provide SDR BT.709 ISO (isolated/independent)
camera feeds to other broadcasters.
− In such circumstances, the SDR camera outputs can
be recorded and output directly, but HDR cameras
should be converted to SDR BT.709 using a scene-
light conversion to match the native SDR cameras.
− Complementary scene-light down-mapping and
scene-light up-mapping can be used on the input
and output of the replay servers, to minimise the
“round-trip” losses.
C
V
CV
C
V
HDR cameras
HDR Signal
138

C
V
CV
C
V
HDR cameras
HDR Signal
139
− To ensure the highest quality SDR output,
cameras are shaded using an SDR monitor
fed via identical HDR to SDR converters to
those used on the main programme output.
− In the case of the BBC trial illustrated in Fig. 2,
a scene-light conversion was used for the
cameras covering the main football match
(“Match”) and a display-light conversion
was used for the cameras covering the
presentation (“Pres”) studio.

C
V
CV
C
V
HDR cameras
HDR Signal
140
− Where the “Clean or World Feed” is
considered the main output, it may be via
a scene-light converter.
− Where the broadcaster’s SDR services is
considered the main output (SDR TX output
or Dirty), it should be via a display-light
converter.
− In practice, the differences between the two
may be small, and within the usual range of
artistic tolerances for SDR production.

− Changes in exposure of the image may be more visible in the HDR output than the SDR output.
⇒ So rapid adjustments in exposure whilst shading in SDR should be avoided.
− Under controlled studio lighting, a possible option may be to shade the cameras using the HLG
backwards compatible SDR picture, rather than via a dedicated HDR to SDR converter.
• In this case, the SDR shading monitor should be set to a display gamma of 2.2 with BT.2020 colour, to
resemble a typical display-light conversion from HLG to SDR as shown on a BT.1886 (gamma 2.4)
production monitor.
• However, under variable lighting conditions or in territories where SDR skin tones are set brighter, a
dedicated HDR to SDR converter is preferred.
141
Display Gamma of 2.2
with BT.2020 Colour

− The SDR monitors used for camera shading should be separated from the HDR check monitor that is used
to ensure that high quality HDR output is being maintained (indicated as “Vision Guarantee” in the figure).
− In the BBC live production trial occasional checks of the HDR output by a vision supervisor were found to
be sufficient, with operators concentrating on the SDR monitors used for camera shading.
142

− The BBC also found that in some situations, for example within the confined space of an outside broadcast
truck, it is not practicable to achieve complete separation between the SDR and HDR monitors in the
control room.
• As critical monitoring is in SDR, to avoid camera shader operators being affected by glare from an
HDR check monitor, the nominal peak luminance of the HLG HDR monitor can be reduced, for
example to 600 𝐜𝐝/𝐦 𝟐
(with an appropriate gamma adjustment) to reduce the disturbance.
HLG Display Gamma
Nominal Peak
Luminance (cd/m²)
Display
Gamma
400 1.03
600 1.11
800 1.16
1 000 1.20
1 500 1.27
2 000 1.33
143

− A fundamental difference between Fig. 2 and Fig. 1 is that here, in Fig. 2, an additional scene-light SDR
output signal is provided with the “traditional” BT.709 look, whilst the HLG HDR signal and display-light SDR
signal have the HLG look.
− By design, if no further artistic adjustments are made, HLG signals preserve the chromaticity of the scene
as imaged by the camera, when compared with the “traditional” looks of SDR BT.709 and BT.2020
cameras (as described in Report ITU-R BT.2390).
Fundamental Difference between SDR and HDR Focussed Production
Fig. 1 Fig. 2
144
“traditional”
BT.709 Look
HLG look
HLG look
HLG look
HLG look

SDR Focussed Production Notes, Summary
− The “clean or World Feed” SDR signal may be derived from the HDR signal using a scene-light conversion, to match other
broadcasters’ SDR cameras that may also be present at the venue.
− For any SDR output containing graphics (e.g. for the broadcaster’s own SDR service) a display-light conversion is
recommended, as that should ensure the same hue and saturation of graphics in both HDR and SDR outputs.
− SDR graded content should be inserted into the programme using display-light direct mapping or up-mapping, to
preserve its original “look” and the artistic intent; SDR graphics should be directly mapped into the HDR format.
− A host broadcaster may be required to provide SDR BT.709 ISO (isolated/independent) camera feeds to other
broadcasters. In such circumstances, the SDR camera outputs can be recorded and output directly, but HDR cameras
should be converted to SDR BT.709 using a scene-light conversion to match the native SDR cameras.
− Where the “clean or World Feed” is considered the main output, it may be via a scene-light converter. Where the
broadcaster’s SDR services is considered the main output (SDR TX output), it should be via a display-light converter.
• In practice, the differences between the two may be small, and within the usual range of artistic tolerances for SDR
production.
− An additional scene-light PQ to SDR BT.709 conversion may also be included for colour matching with downstream SDR
BT.709 cameras.
145

Further Details for HLG Production
− Some HDR cameras conveniently provide parallel HDR and SDR signal outputs.
• Where that is the case, the cameras can be shaded using their SDR output, and the HDR output
allowed to follow with a fixed “gain offset” (equivalent to an exposure offset) relative to the SDR.
− This approach relies on the SDR and HDR camera outputs precisely tracking one another, which may not
always be the case.
− Operational staff may also have concerns about shading the cameras using a signal that is not exactly
the same as that being used to feed their main SDR output (i.e. shading is done on HDR signal).
146
SDR gain adjustment
Optimal brightness
ranges both for 4K
HDR and HD SDR
Parallel HDR and SDR workflow
(Gain) (Iris)

− Shading the cameras using an SDR output allows the HDR signals to be created in such a way that they
closely follow the reference levels specified in the table, and are therefore well-conditioned for
conversion to SDR.
• This is achieved by applying the fixed gain to the linear HDR signal such that a 90% reflectance
object is portrayed with a 100% signal level in the SDR signal, and a 73% signal level in the HLG HDR
signal.
− In the SDR signal used for shading, highlights greater than the super-white signal level (109%) are lost, but
they are retained in the HDR signal.
147
SDR gain adjustment
Optimal brightness
ranges both for 4K
HDR and HD SDR
Parallel HDR and SDR workflow
(Gain) (Iris)

− When this approach is used for the main cameras, those cameras that only provide an HDR output should
be shaded using a scene-light conversion to SDR.
− The scene-light conversion will provide images that more closely resemble those from traditional SDR
cameras (and any HDR camera with SDR outputs) that may also be included in the production.
− To ensure that the HDR signals comply with the levels specified in the table, and to better match those of
SDR cameras (in situations when a “knee” is not used), a hard clip to SDR rather than tone mapping is
preferred.
Reflectance Object or Reference
Nominal Luminance Value
(PQ & HLG)
[Display Peak Luminance, 1000 nit]
Nominal Signal
Level (%)
PQ
Nominal Signal
Level (%)
HLG
Greyscale Chart Max (83% Reflectance) 162 nit 56 71
Greyscale Chart Max (90% Reflectance) 179 nit 57 73
Reference Level:
HDR Reference White (100% Reflectance) also Diffuse
White and Graphics White
203 nit 58 75
148

For the final programme output, two methods of converting from HDR to SDR are illustrated. Large
productions may be required to support both:
1- Display Light Tone Mapping
− It should be used to preserve the appearance of the HDR signal when converting to SDR.
− Ideally the tone-mapping should be matched to any inverse tone mapping used elsewhere in the
production, thereby minimising the SDR-HDR-SDR “round-tripping” losses.
149
“traditional”
BT.709 Look
HLG look
SDR with HLG look

2- Scene Light Tone Mapping
− It should be used to ensure maximum compatibility with conventional SDR productions.
• For example, where the converted SDR output is made available to other broadcasters for mixing
with their own SDR cameras covering the same event
• For example, when the final SDR output must correspond precisely with the pictures seen by the
shader or camera operator.
 This can be achieved by shading (or “racking”) the cameras in SDR and providing a scene-light
conversion from HDR to SDR at the output.
150
“traditional”
BT.709 Look
HLG look
SDR with HLG look

SDR-HDR and HDR-SDR Format Conversion
Signal
Conversion Type SDR to PQ PQ to SDR HLG to PQ
Scene-light Display-light Direct mapping Up-mapping Hard Clip Down-mapping Trans-coding
Graded Content
SDR Graded Inserts P P (1) P (2)
HLG Graded Inserts P P
Cameras
SDR Camera
(Relaxed Clippers for BT.709)
P (4) P
HLG Camera P P
Graphics
SDR Matching Colour Branding P P
SDR Matching In-vision Signage P P
SDR Output(3)
SDR Complete Programme P P
SDR For Downstream Mixing with
SDR Cameras
P P
(1) Direct mapping faithfully maintains the original SDR look.
(2) Up-mapping adjusts the distribution of highlights of the original SDR look.
(3) SDR Output refers to conversion from HDR to both the final programme output as well as the SDR shading/check monitor.
(4) In PQ based production, the difference between display-light and scene-light conversion of BT.2020 signals is relatively minor (see Report ITU-R BT.2390) and current practice is
to use display-light conversion. Conversion from BT.709 to BT.2020 is defined in Recommendation BT.2087.
151
Suggested Format Conversions for PQ Live Production

SDR-HDR and HDR-SDR Format Conversion
Signal
Conversion Type SDR to HLG HLG to SDR PQ to HLG
Scene-light Display-light Direct mapping Up-mapping Hard Clip
Down-
mapping
Trans-
coding
Graded Content
SDR Graded Inserts P P (1) P (2)
PQ Graded Inserts P P
Cameras
To Switcher
SDR Camera
(Relaxed Clippers For BT.709)
P P
PQ Camera P P
To Shading
HDR Camera with SDR
Shading
P P
SDR Camera with HDR
Shading
P P
Graphics
SDR Matching Colour
Branding
P P
SDR Matching In-vision
Signage
P P
SDR Output(3)
SDR Complete Programme P P
SDR for Downstream
Mixing With SDR Cameras
P P
(1) Direct mapping faithfully maintains the original SDR look.
(2) Up-mapping adjusts the distribution of highlights of the original SDR look.
(3) SDR Output refers to conversion from HDR to both the final programme output as well as the SDR shading/check monitor.
152
Suggested Format Conversions for HLG Live Production

153
Signal Source
BBC Conversion
LUT
Conversion Type SDR to HDR HDR to SDR HDR to HDR
Scene-Light Display-Light
Direct
Mapping Up-Mapping Hard Clipping Down-Mapping Conversion
Graded
Content
SDR graded inserts 1
5 P P
SDR graded programmes 3 P P
HLG graded content 8 P P
PQ graded content 1 or 2 P P
Camera
to
switcher
SDR BT.709 camera 2
6 P P
S-Log3 camera 10 P P
"S-Log3 Live" camera 11 P P
Camera
to
SDR
shading
3
HDR camera (display-light priority) 8 P P
HDR cameras (scene-light priority) 12 P P
SDR camera (HDR workflow) SDR > HDR > SDR (display-light
priority)
6 and 8 P P P P
SDR camera (HDR workflow) SDR > HDR > SDR (scene-light
priority)
6 and 12 P P P
Graphics
SDR matching colour branding 3 P P
SDR matching in-vision signage 4 P P
Programme
Output
SDR "dirty" (with graphics) 8 P P
SDR "clean" (no graphics) for mixing with unilateral SDR
cameras 4
12 P P
PQ for onward distribution 7 P P
Note 1: Modest highlight "boost" to improve match with native HDR (100% SDR -> ~83% HLG)
Note 2: Small highlight "boost" to improve match with native HDR cameras (100% SDR -> ~79% HLG)
Note 3: Display-light shading where "dirty" output has priority, scene-light shading where "clean" output has priority
Note 4: Emulates SDR camera with some soft clipping of highlights
SDR-HDR and HDR-SDR Format Conversion (BBC Conversion LUTs)

The Displayed “look” of Content Following Format Conversion
− SDR to HDR and HDR to SDR format conversion may change the displayed look of content.
− Next tables summarise the look of content for HLG and PQ live production, after the format conversions
specified in previous tables.
− One notable consideration is the possible change of look occurring when the input and output
conversion types do not match (next slide).
• Scene-light conversion to SDR should therefore be used with care, and multiple such conversions
should be avoided.
− Graded content does not carry a specific SDR or HDR look, but instead has an artistic look imposed upon
it by the colourist.
154

SDR
BT.709 (Traditional)
155

HLG (BT.2100 ɣ1.2)
(Natural)
156

− One notable consideration is the possible change of look occurring when the input and output
conversion types do not match.
• Scene-light HDR to SDR format conversion, necessary for downstream mixing with SDR BT.709
cameras, may cause some SDR graded content (inserted via display-light conversion) to appear
more saturated than intended for HLG HDR production, or slightly less saturated than intended for PQ
HDR production.
157
More saturated
than intended
for HLG HDR
production
HLG HDR
Slightly less
saturated than
intended for PQ
HDR production.
PQ HDR
PQ HDR
HLG HDR

Display Look of Content after Format Conversion for HLG Production
Signal
Input conversion type SDR output conversion following HLG production
Scene-light Display-light
Scene-light(1) Display-light(2)
To BT.709 To BT.2020 BT.709 and BT.2020
Graded Content
SDR Graded Inserts P Over Saturated Over Saturated
Maintaining Artistic
Intent(4)
PQ Graded Inserts P Over Saturated Over Saturated
Intent(4)
Cameras
To Switcher
Sdr BT.709 Camera P SDR BT.709 Look SDR BT.2020 Look HLG Look(3)
Sdr BT.2020 Camera P SDR BT.709 Look SDR BT.2020 Look HLG Look(3)
To Shading
HDR Camera With SDR Shading P SDR BT.709 Look SDR BT.2020 Look HLG Look(3)
SDR Camera With HDR Shading P SDR BT.709 Look SDR BT.2020 Look HLG Look(3)
Graphics
SDR Matching Colour Branding P Over Saturated Over Saturated
Intent(4)
SDR Matching In-vision Signage P SDR BT.709 Look SDR BT.2020 Look HLG Look(3)
(1) Scene-light conversion is used to match downstream SDR cameras but is not the preferred method for SDR output conversion.
(2) Display-light conversion is generally the preferred SDR output method and will preserve the look of graded content and graphics that originated in SDR or PQ.
(3) HLG, SDR BT.2020 and SDR BT.709 have different looks.
(4) Graded Content and Graphics content do not necessarily have the native SDR or HLG look. The "Artistic Intent" may have been to make them more saturated,
have different contrast, etc.
158

Display Look of Content after Format Conversion for PQ Production
Signal
Input conversion type SDR output conversion following PQ production
Scene-light Display-light
Scene-light(1) Display-light(2)
To BT.709 To BT.2020 BT.709 and BT.2020
Graded Content
SDR Graded Inserts P Slightly Under Saturated Similar to Artistic Intent
Intent(4)
HLG Graded Inserts P Slightly Under Saturated Similar to Artistic Intent
Intent(4)
Cameras
SDR Camera P SDR BT.709 Look SDR BT.2020 Look PQ Look(3)
HDR Camera P SDR BT.709 Look SDR BT.2020 Look PQ Look(3)
Graphics
SDR Matching
Colour Branding
P Slightly Under Saturated Similar to Artistic Intent
Intent(4)
SDR Matching In-
vision Signage
P SDR BT.709 Look SDR BT.2020 Look PQ Look(3)
(1) Scene-light output conversion may be appropriate for an SDR Output that needs to match with secondary production cameras.
(2) Display-light conversion is generally the preferred SDR output method and will preserve the look of graded content and graphics that also
originated in SDR, or HLG.
(3) PQ and SDR BT.2020 have a similar look.
(4) Graded content and graphics content do not necessarily have a native SDR or PQ look. The “Artistic Intent” may have been to make them more
saturated, have different contrast, etc.
159

Resulting Looks after HDR-to-SDR Down-conversion and Up-conversion
160

Mapping Overview of the Available Transfer Characteristics
161
− Mapping overview of the available transfer characteristics regarding Scene Light Mapping and Display
Light Mapping
− Mapping Type (SL = Scene Light, DL = Display Light)

162
Relevant Cases of PQ and HLG Looks

Resulting Looks when Cross-converting from PQ to HLG
163

Legacy Equipment Considerations for HDR to SDR Conversion
− When converting signals from HDR to SDR, one approach is to hard clip the HDR signal so that signals
below a given threshold (e.g. HDR Reference White) are mapped into the SDR signal range, and signals
above the threshold are lost.
− This approach works well when the HDR signal is tightly controlled (for example by using the production
workflow described in further details for HLG production) to ensure that critically important image detail
lies below the clipping threshold.
− However, to allow the SDR signal to benefit from the HDR production workflow, down-mapping (tone-
mapping) is preferred.
164
Clipped Highlights and Shadows
This approach works well when the
critically important image detail lies
below the clipping threshold.

165
− When converting from HDR to SDR, better pictures can be created using “tone-mapping”, rather than the
hard-clipping.
− Tone-mapping compresses the highlights rather like a soft-clipper or camera “knee”.
Example tone-mapping curve

− With down-mapping, HDR highlights (for example signals
above HDR Reference White) are compressed to lie within
the upper portion of the SDR signal range.
− Signals at and below the HDR Reference White level will
occupy the remaining SDR signal range.
− The level at which HDR Reference White is mapped to the
SDR signal range is chosen to balance the overall
brightness of the SDR image (including graphics) and the
amount of detail that is preserved in the image highlights.
166
Preferred Min.
Preferred Max.
(Narrow
Range)
(White)
(Black)
(super-whites)
(sub-blacks)
Compressed Highlights and Shadows
HDR Reference White

− The SDR “super-white” code value range (i.e. signals
above nominal peak white) is intended to accommodate
signal transients and ringing which help to preserve signal
fidelity after cascaded processing (e.g. filtering, video
compression).
− In situations where it is known that these signals will not be
clipped, they may also be exploited to preserve additional
highlights after HDR to SDR down-mapping.
− However, in other situations (e.g. use of some legacy
equipment), “super-white” and/or “sub-blacks” could be
clipped.
• In such situations, detail that is critical to the artistic
rendition of an image should not be placed in the SDR
super-white region after conversion.
167
Preferred Min.
Preferred Max.
(Narrow
Range)
(White)
(Black)
(super-whites)
(sub-blacks)
Compressed Highlights and Shadows
HDR Reference White

SDR-HDR-SDR “Round-Tripping”
− The SDR signals will be converted to HDR during production and back again to SDR for distribution.
− This is the process known as “round-tripping”.
− Ideally, the process of round-tripping would be transparent.
− However, in practice, this is difficult to achieve and is the subject of on-going investigation.
− To understand the difficulties that can arise it is helpful to consider the individual processes of up-
mapping to HDR and down-mapping to SDR.
168
“traditional”
BT.709 Look
HLG look
HLG look
HLG HDR

− There are two main approaches to including SDR content in HDR programmes:
• Direct Mapping
• Up-mapping
169
“traditional”
BT.709 Look
HLG look
HLG look
HLG HDR
Typically, HDR to SDR
conversion uses a non-
linearity, similar (and
analogous) to the “knee”
function found in cameras.
This non-linear mapping
reduces the dynamic range
of highlights but does not
completely remove them.

− In both up-mapping and down-mapping, careful
attention should be paid to those “diffuse” parts of the
scene that can be supported in both SDR and HDR
formats.
− However, this is made difficult by variation of the scene
luminance factor corresponding to reference white (100%
SDR signal) in SDR productions.
− SDR signals provide little “headroom” for highlights.
− Some SDR signals are simply clipped of most of the
highlight information (e.g. live sport), but in other cases
include more highlights through the use of a camera
“knee” (e.g. drama or sport “beauty” shots).
− The optimum techniques for up-mapping followed by
down-mapping are still under investigation. 170

171
HLG look
HLG HDR
PQ look
PQ HDR
− It should also be noted that after “round-tripping”
(SDR>HDR>SDR) within a production using Display Light
Mapping for up-conversion and Scene Light Mapping
for down-conversion, any SDR material (e.g. graded
inserts or graphics) will show a difference in saturation
at the end of the signal chain compared to the
original SDR version. The result will appear
• more saturated than intended in the case of HLG
production
• slightly less saturated than intended for PQ
production
− For this reason, scene light and display light conversion
in combination should be used with care and multiple
conversions of such kind should be avoided.
More Saturated
Than Intended
Less Saturated
Than Intended

Improved Color Volume Management in HDR to SDR Conversion
172
− The tone-mapping can be arranged to complement the inverse tone-mapping used in the SDR to HDR
“up-conversion”, to minimize “round-tripping” losses.
− Furthermore, unlike a typical camera “knee”, the tone-mapping and inverse tone-mapping can both be
applied in the luminance domain, thereby avoiding any hue distortions through the conversion process.
− Some loss is, however, inevitable, as the very best inverse tone-mapper is seldom the exact inverse of the
very best tone-mapper.
Example tone-mapping curve

Improved Color Volume Management in HDR to SDR Conversion
173
− As an example, is recommend that an inverse tone-mapper for live production converts a 100% SDR input
signal to a maximum of 83% HLG signal, but is also recommend that a tone-mapper takes account of the
entire HLG HDR signal and converts a 100% HLG signal to 100 % SDR.
− The SDR to HDR to SDR “round-tripping” losses for such converters, cascaded back-to-back, are illustrated
in the figure for monochrome signals.
Typical SDR to HDR to SDR "round-tripping” performance
83% HLG
signal
100 % SDR

Signal Line-up
− Prior to any live transmission, it is common practice for broadcasters to check the end-to-end integrity of
the production and contribution signal chain.
• Typically a signal generator producing colour bars and a lipsync test, is fed into the production
switcher or matrix.
• The video waveform and lipsync is then checked for accuracy at various points along the chain,
including the broadcaster’s MCR (Master Control Room).
174

Signal Line-up
− If BT.2111 Colour Bars are used as the signal source, after any HDR to SDR conversion (e.g. to feed an SDR
contribution circuit) the wide colour gamut bars within the test pattern should not be expected to land on
the colour bar targets of a standard BT.709 vectorscope; as the SDR BT.709 and HDR BT.2100 colour
primaries are different, the true displayed colours of the respective primary (red, green, blue) and
secondary (yellow, cyan, magenta) colour bar signals are also different.
175
COLORIMETRY
BT.2020
Vectorscope
HLG Original

Signal Line-up
− The BT.709 colour bars within the BT.2111 test pattern may also not land on the colour bar targets after
conversion, as their luminance could be affected by any tone-mapping from HDR to SDR.
− Work is currently underway to design test patterns for signal line-up that should provide a predictable
output after display-light and scene-light HDR to SDR conversion.
176
SDR Original
COLORIMETRY
BT.709
Vectorscope

177
SDR Original HLG
SDR
HLG Original
Signal Line-up

Use EBU “HDR Line-Up Bars” – Intended to Survive Down-mapping
178
75% SDR BT.709 Bars Display-light direct mapped
75% SDR BT.709 Bars Scene-light direct mapped

Effect of LUT Hardware on Output
179
An “ideal” down-mapper” will re-construct 75% BT.709 bars
In practice 3D-LUT interpolation errors slightly degrade the signal
R G B
Inputs to the hardware
interpolator must be
positive, therefore, near
black, interpolation can
be incorrect.

Effect of LUT Hardware on Output
180
Vector-scope showing typical 3D-LUT errors
In practice 3D-LUT interpolation errors slightly degrade the signal

– Seamless HDR productions (UHD and HD)
– It brings HDR capabilities to all inputs and outputs of production switcher.
– The technology seamlessly handles SDR and HDR in parallel for Sports, News and Light Entertainment
productions.
HDR Capable in Switchers, Routers,…
– For example FormatFusion4 supports the Electrical Optical Transfer
Functions (EOTF) for:
• Realtime control of Perceptual Quantizer (PQ)
• Realtime control of Hybrid Log Gamma (HLG)
• Sony S-Log3 profile
– FormatFusion4 also includes color space support for Wide Color Gamut
(BT709 and BT2020) in all formats (1080i, 1080p and UHD).
– Because of no Metadata in SDI for HDR (Except Colorimetry), the
formats setting should be done manually by user for I/Os (before 2018).
181

Real Time HDR/WCG Conversion with the Colorfront Engine™ Video Processing
FS-HDR
182
$7,995.00

− FS-HDR has been designed to get us all there faster with a low profile, stand-alone, and real time device
uniquely designed to bridge SDR to HDR, HDR to SDR, and HDR to HDR, all in real time.
• HDR Conversions:
 HDR to HDR
 HDR to SDR
 SDR to HDR
• WCG Conversions:
 BT.709 and BT.2020
• Up and Down Conversions:
 Converting HD SDR BT.709 sources to UltraHD HDR BT.2020
 Converting UltraHD HDR BT.2020 sources to HD SDR BT.709 or HD HDR BT.2020
183

− Colorfront Engine in Film Mode offers built-in LOOK selection including film stock emulation and popular
aesthetic looks, valuable tools for on-set and episodic production and you can even mix between any
two for unique specific aesthetic needs:
LOOK
• Look A or B Select
MasterLook, MasterBroadcast, MasterLookBright, MasterLookCool, MasterLookLowCon,
MasterLookSoftColor, MasterLookVivid, MasterLookWarm, MasterPastelD60, MasterPastelD65, Agfa, ARRI
K1S1, Bleach, ClassicFilm, Ektachrome, FilmBlended, FilmBlendedLoCon, FujiDI, FujiXD, GenericFilm,
Kodachrome. ReversalClassic
• A/B Mix
184

− Colorfront Engine in Film Mode offers built-in LOOK selection including film stock emulation and popular
aesthetic looks, valuable tools for on-set and episodic production and you can even mix between any
two for unique specific aesthetic needs:
LOOK
• Look A or B Select
MasterLook, MasterBroadcast, MasterLookBright, MasterLookCool, MasterLookLowCon,
MasterLookSoftColor, MasterLookVivid, MasterLookWarm, MasterPastelD60, MasterPastelD65, Agfa, ARRI
K1S1, Bleach, ClassicFilm, Ektachrome, FilmBlended, FilmBlendedLoCon, FujiDI, FujiXD, GenericFilm,
Kodachrome. ReversalClassic
• A/B Mix
185

Inputs: Dynamic Range/Color Gamut
• SDR BT.709 100 Nits
• SDR Extended BT.709
• PQ BT.2020 1000 Nits
• PQ P3D65 1000 Nits
• Hybrid Log Gamma BT.2100
• HLG Extended BT.709
• Sony® S-Log3 S-Gamut3
• Sony S-Log3 S-Gamut3 Cine
• Sony S-Log3 BT.2020
• ARRI Log C Wide Gamut
• Panasonic® V-Log
• RED Log3G10 Wide Gamut
• Canon Log 2
• Canon Log 3
• ACEScct
Outputs: Dynamic Range/Color Gamut
• SDR BT.709 100 Nits
• SDR Extended BT.709
• PQ BT.2020 1000 Nits
• PQ P3D65 1000 Nits
• Hybrid Log Gamma BT.2100
• Sony S-Log3 S-Gamut3
• Sony S-Log3 BT.2020
• ARRI Log C Wide Gamut
• ACEScct
186

BBC HLG LUTs Mode
− BBC HLG LUTs Mode offers additional functionality that adds HDR conversion options, particularly for
television broadcasters who are looking for specific conversion criteria.
• Supports mathematical HLG HDR dynamic range mapping per ITU BT.2408
• Scene-light and Display-light conversions
• SDR, PQ, and S-Log3 to HLG
• HLG to SDR and PQ
• Utilizes 33 point Tetrahedral 3D LUT Interpolation
187

HDR and WCG Principles-Part 6

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