EN 61966-2-1:2000/A1:2003

Multimedia systems and equipment - Colour measurement and management - Part 2-1: Colour management - Default RGB colour space - sRGB

Multimediasysteme und -geräte - Farbmessung und Farbmanagement - Teil 2-1: Farbmanagement - Vorgabe-RGB-Farbraum - sRGB

Mesure et gestion de la couleur dans les systèmes et appareils multimédia - Partie 2-1: Gestion de la couleur - Espace chromatique RVB par défaut - sRVB

Multimedia systems and equipment - Colour measurement and management - Part 2-1: Colour management - Default RGB colour space - sRGB (IEC 61966-2-1:1999/A1:2003)

General Information

• Status: Published
• Publication Date: 14-May-2003
• Withdrawal Date: 28-Feb-2006
• ICS: 33.160.60 - Multimedia systems and teleconferencing equipment
• ICS: 37.080 - Document imaging applications
• Technical Committee: CLC/TC 100X - Audio, video and multimedia systems and equipment and related sub-systems
• Drafting Committee: IEC/TC 100 - IEC_TC_100
• Parallel Committee: IEC/TC 100 - IEC_TC_100
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 15-May-2003
• Completion Date: 23-Sep-2025
• Ref Project: SIST EN 61966-2-1:2001/A1:2003 - Multimedia systems and equipment - Colour measurement and management -- Part 2-1: Colour management - Default RGB colour space - sRGB

Relations

• Amends: EN 61966-2-1:2000 - Multimedia systems and equipment - Colour measurement and management - Part 2-1: Colour management - Default RGB colour space - sRGB
• Effective Date: 29-Jan-2023

Overview

EN 61966-2-1:2000/A1:2003 (IEC 61966-2-1:1999/A1:2003) specifies the default RGB colour space - sRGB and extends the original standard with Amendment A1. It is a European/CENELEC adoption prepared by IEC TC 100 and ISO TC 42, providing formal colourimetric definitions, transfer functions and encoding/decoding transforms to ensure consistent colour reproduction across multimedia systems and equipment.

Key topics

• Definition of sRGB colour space: reference conditions, non‑linear transfer (gamma-like) and the mapping between sR′G′B′ and linear device values.
• Colourimetric transforms: matrices and equations to convert between sRGB (non-linear and linear) and CIE 1931 XYZ tristimulus values are provided.
• sYCC (Annex F - normative): a default Y′CbCr (luma‑chroma) encoding transformation for a standard luma‑chroma‑chroma space called sYCC. Includes:
  • Equations for encoding/decoding between sYCC and sRGB/CIE XYZ.
  • Quantization rules and default 24‑bit (8‑bit/channel) encoding behavior.
  • Rules for handling out‑of‑gamut tristimulus values (values <0 or >1 retained in sYCC).
• bg‑sRGB and bg‑sYCC (Annex G - informative): recommendations for extended‑gamut encoding (called bg‑sRGB) including default parameters (e.g., 10‑bit/ channel defaults WDC/KDC values) and corresponding YCC transforms.
• CIELAB transformation (Annex H - informative): normative references for converting to/from CIELAB (Lab*).
• Quantization and bit‑depth guidance: default bit depths (8‑bit for sYCC; 10‑bit/30‑bit for bg‑sRGB) and formulas for N‑bit encodings are specified.

Applications

• Implementing colour management in operating systems, browsers, image editors and multimedia players to ensure consistent on‑screen colour.
• Encoding and decoding image and video pipelines (JPEG, video codecs, streaming) that rely on Y′CbCr/YCC transforms.
• Display and camera firmware that maps sensor or frame buffer values to the sRGB reference.
• Graphics, web and digital photography workflows where sRGB is the default working space for cross‑device interoperability.
• Extended‑gamut workflows that require bg‑sRGB/bg‑sYCC support (high bit‑depth video, professional imaging).

Who should use this standard

• Colour scientists and imaging engineers
• Software developers (renderers, browsers, color management systems)
• Hardware manufacturers (displays, cameras, capture cards)
• Multimedia system integrators and standards implementers

Related references / keywords

• IEC 61966-2-1, sRGB, colour management, default RGB colour space, sYCC, bg-sRGB, CIE 1931 XYZ, ITU‑R BT.601 (coefficients referenced).

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2003
Multimedia systems and equipment - Colour measurement and management - Part
2-1: Colour management - Default RGB colour space - sRGB (IEC 61966-2-
1:1999/A1:2003)
Multimedia systems and equipment - Colour measurement and management -- Part 2-1:
Colour management - Default RGB colour space - sRGB
Multimediasysteme und -geräte - Farbmessung und Farbmanagement -- Teil 2-1:
Farbmanagement - Vorgabe-RGB-Farbraum - sRGB
Mesure et gestion de la couleur dans les systèmes et appareils multimédia -- Partie 2-1:
Gestion de la couleur - Espace chromatique RVB par défaut - sRVB
Ta slovenski standard je istoveten z: EN 61966-2-1:2000/A1:2003
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
33.160.60 9HþSUHGVWDYQLPXOWLPHGLMVNL Multimedia systems and
VLVWHPLLQRSUHPD]D teleconferencing equipment
WHOHNRQIHUHQFH
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 61966-2-1/A1
NORME EUROPÉENNE
EUROPÄISCHE NORM May 2003
ICS 33.160.60; 37.080
English version
Multimedia systems and equipment -
Colour measurement and management
Part 2-1: Colour management -
Default RGB colour space - sRGB
(IEC 61966-2-1:1999/A1:2003)
Mesure et gestion de la couleur  Multimediasysteme und -geräte -
dans les systèmes et appareils multimédia Farbmessung und Farbmanagement
Partie 2-1: Gestion de la couleur - Teil 2-1: Farbmanagement -
Espace chromatique RVB par défaut - Vorgabe-RGB-Farbraum -
sRVB sRGB
(CEI 61966-2-1:1999/A1:2003) (IEC 61966-2-1:1999/A1:2003)

This amendment A1 modifies the European Standard EN 61966-2-1:2000; it was approved by CENELEC
on 2003-03-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this amendment the status of a national standard without any
alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This amendment exists in three official versions (English, French, German). A version in any other language
made by translation under the responsibility of a CENELEC member into its own language and notified to the
Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61966-2-1:2000/A1:2003 E

Foreword
The text of document 100/555A/FDIS, future amendment 1 to IEC 61966-2-1:1999, prepared by
IEC TC 100, Audio, video and multimedia systems and equipment, was submitted to the IEC-
CENELEC parallel vote and was approved by CENELEC as amendment A1 to EN 61966-2-1:2000 on
2003-03-01.
The following dates were fixed:
– latest date by which the amendment has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2003-12-01
– latest date by which the national standards conflicting
with the amendment have to be withdrawn (dow) 2006-03-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex F is normative and annexes G and H are informative.
__________
Endorsement notice
The text of amendment 1:2003 to the International Standard IEC 61966-2-1:1999 was approved by
CENELEC as an amendment to the European Standard without any modification.
__________
INTERNATIONAL IEC
STANDARD
61966-2-1
AMENDMENT 1
2003-01
Amendment 1
Multimedia systems and equipment –
Colour measurement and management –
Part 2-1:
Colour management –
Default RGB colour space - sRGB
Amendement 1
Mesure et gestion de la couleur dans les systèmes
et appareils multimédia –
Partie 2-1:
Gestion de la couleur –
Espace chromatique RVB par défaut - sRVB
 IEC 2003 Droits de reproduction réservés  Copyright - all rights reserved
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail]  Web: www.iec.ch
PRICE CODE
P
For price, see current catalogue

– 2 – 61966-2–1 Amend. 1  IEC:2003(E)
FOREWORD
This amendment has been prepared by Technical Area 2: Colour measurement and
management, of IEC technical committee 100: Audio, video and multimedia systems
and equipment and ISO TC 42: Photography.
The text of this amendment is based on the following documents:
FDIS Report on voting
100/555A/FDIS 100/625/RVD
Full information on the voting for the approval of this amendment can be found in the report on
voting indicated in the above table.
It is published as a double logo standard.
In the ISO the Standard has been approved by 10 P-members out of 10 having cast the vote.
_____________
Page 5
CONTENTS
Add the titles of Annexes F, G and H as follows:
Annex F (normative) Default YCC encoding transformation for a standard luma-chroma-
chroma colour space: sYCC
Annex G (informative) Extended gamut encoding for sRGB: bg-sRGB and its YCC
transformation: bg-sYCC
Annex H (informative) CIELAB (L*a*b*) transformation
Page 49
Add the following new Annexes F, G and H after Annex E:

61966-2–1 Amend. 1  IEC:2003(E) – 3 –
Annex F
(normative)
Default YCC encoding transformation for a
standard luma-chroma-chroma colour space: sYCC
The method of digitization in this annex is designed to complement current sRGB-based colour
management strategies by explicitly standardizing a default transformation between sRGB and
a standard luma-chroma-chroma colour space (sYCC). Application and hardware developers
who want to support various colour compression schemes based on luma-chroma-chroma
spaces can utilize this annex. Since this sYCC colour space is a simple extension of the sRGB
colour space as defined in this standard, the same reference conditions are shared by both
colour spaces.
F.1 General
The encoding transformations between sYCC values and CIE 1931 XYZ values provide
unambiguous methods to represent optimum image colorimetry when viewed on a hypothetical
reference display that is capable of producing all colours defined by sYCC encoding, in the
reference viewing conditions by the reference observer. Non-linear floating point sR′G′B′
represent the appearance of the image as displayed on the reference display in the reference
viewing condition described in Clause 4 of this standard.
F.2 Transformation from sYCC values ( Y , Cb , Cr ) to CIE 1931 XYZ
sYCC sYCC sYCC
values
The non-linear sY′C ′C′ values can be computed using the following relationship:
b r
′
Y =()Y − KDC(WDC − KDC)
sYCC sYCC
′ (F.1)
Cb =()Cb − Offset Range
sYCC sYCC
Cr′ =()Cr − Offset Range
sYCC sYCC
For 24-bit encoding (8-bit/channel), WDC = 255, KDC = 0, Range = 255, and Offset = 128, and
the relationship is defined as;
′
Y = (Y − 0)()255 − 0 = Y 255
sYCC sYCC sYCC
(8) (8)
Cb′ =()Cb −128 255 (F.2)
sYCC sYCC
(8)
′
Cr =()Cr −128 255
sYCC sYCC
(8)
24-bit encoding (8-bit/channel) shall be the default sYCC encoding bit depth. Other bit depths
may be unsupported for general use.
Where other N-bit/channel encoding is supported ( N > 8), the relationship is defined as;

– 4 – 61966-2–1 Amend. 1  IEC:2003(E)
N
′
Y = Y (2 −1)
sYCC sYCC
(N)
N −1 N
Cb′ =()Cb − 2 ()2 −1 (F.2′)
sYCC sYCC
(N)
N −1 N
′
Cr =()Cr − 2 ()2 −1
sYCC sYCC
(N)
For 24-bit encoding (8-bit/channel), the non-linear sY′C ′C′ values are transformed to the non-
b r
linear sR′G′B′ values as follows;
R′ 1,000 0 0,000 0 1,402 0 Y ′
    
sRGB sYCC
    
′ ′
G = 1,000 0 − 0,344 1 − 0,714 1 Cb (F.3)
sRGB sYCC
    
 ′    ′ 
B 1,000 0 1,772 0 0,000 0 Cr
 sRGB   sYCC
For N-bit/channel encoding ( N > 8), it is recommended to replace the matrix coefficients in the
equation F.3 with the coefficients of the inverse matrix of the equation F.12 with enough
accuracy decimal points. For example, following matrix with 6 decimal points has enough
accuracy for the case of 16-bit/channel.
R′ 1,000 000 0,000 037 1,401 988 Y ′
    
sRGB sYCC
    
′ ′
G = 1,000 000 − 0,344 113 − 0,714 104 Cb (F.3′)
sRGB sYCC
    
    
B′ 1,000 000 1,771 978 0,000 135 Cr′
sRGB sYCC
    
The non-linear sR′G′B′ values are then transformed to CIE 1931 XYZ values as follows:
′ ′ ′
If R ,G ,B < −0,040 45
sRGB sRGB sRGB
2,4
′
()− R + 0,055
 
sRGB
R = −
sRGB
 
1,055
 
2,4
′
()− G + 0,055
 
sRGB
G = − (F.4)
sRGB
 
1,055
 
2,4
′
()− B + 0,055
 
sRGB
B = −
sRGB
 
1,055
 
′ ′ ′
If − 0,040 45 ≤ R ,G , B ≤ 0,040 45 ,
sRGB sRGB sRGB
′
R = R ÷12,92
sRGB sRGB
′
G = G ÷12,92 (F.5)
sRGB sRGB
′
B = B ÷12,92
sRGB sRGB
′ ′ ′
If R ,G , B > 0,040 45 ,
sRGB sRGB sRGB
2,4
′
()R + 0,055
 
sRGB
R =
sRGB
 
1,055
 
2,4
′
()G + 0,055
 
sRGB
G = (F.6)
sRGB
 1,055
 
2,4
′
()B + 0,055
 
sRGB
B =
sRGB
 
1,055
 
61966-2–1 Amend. 1  IEC:2003(E) – 5 –
For 24-bit encoding (8-bit/channel), the linear sRGB values are transformed to CIE 1931 XYZ
values as follows:
X 0,412 4 0,357 6 0,180 5R 
sRGB
    
Y = 0,212 6 0,715 2 0,072 2 G (F.7)
sRGB
    
    
Z 0,019 3 0,119 2 0,950 5 B
    sRGB
F.3 Transformation from CIE 1931 XYZ values to sYCC values
( Y , Cb , Cr )
sYCC sYCC sYCC
The CIE 1931 XYZ values can be transformed to non-linear sR′G′B′ values as follows
R 3,240 6 −1,537 2 − 0,498 6 X
    
sRGB
    
G = − 0,968 9 1,875 8 0,041 5 Y (F.8)
sRGB
    
    
B 0,055 7 − 0,204 0 1,057 0 Z
sRGB
    
For N-bit/channel encoding ( N > 8), it is recommended to replace the matrix coefficients in the
equation F.8 with the coefficients of the inverse matrix of the equation F.7 with enough
accuracy decimal points. For example, following matrix with 7 decimal points has enough
accuracy for the case of 16-bit/channel.
R 3,240 625 5 −1,537 208 0 − 0,498 628 6 X
    
sRGB
    
G = − 0,968 930 7 1,875 756 1 0,041 517 5 Y (F.8′)
sRGB
    
    
B 0,055 710 1 − 0,204 021 1 1,056 995 9 Z
sRGB  
   
In the sYCC encoding process, negative sRGB tristimulus values, and sRGB tristimulus values
greater than 1,0 are retained.
If R ,G , B < −0,003 130 8
sRGB sRGB sRGB
()1,0 / 2,4
′
R = −1,055 ×()− R + 0,055
sRGB sRGB
()1,0 / 2,4
′ () (F.9)
G = −1,055 × − G + 0,055
sRGB sRGB
()1,0 / 2,4
′
B = −1,055 ×()− B + 0,055
sRGB sRGB
If − 0,003 130 8 ≤ R ,G , B ≤ 0,003 130 8 ,
sRGB sRGB sRGB
′
R = 12,92 × R
sRGB sRGB
G′ = 12,92 × G (F.10)
sRGB sRGB
′
B = 12,92 × B
sRGB sRGB
– 6 – 61966-2–1 Amend. 1  IEC:2003(E)
If R ,G ,B > 0,003 130 8 ,
sRGB sRGB sRGB
()1,0 / 2,4
′
R = 1,055 ×()R − 0,055
sRGB sRGB
()1,0 / 2,4
′ () (F.11)
G = 1,055 × G − 0,055
sRGB sRGB
()1,0 / 2,4
′
B = 1,055 ×()B − 0,055
sRGB sRGB
The relationship between non-linear sRGB and sYCC is defined as follows:
Y ′ 0,299 0 0,587 0 0,114 0 R′
    
sYCC sRGB
    
′ ′
Cb = − 0,168 7 − 0,331 3 0,500 0 G (F.12)
sYCC sRGB
    
    
Cr′ 0,500 0 − 0,418 7 − 0,081 3 B′
sYCC sRGB
    
NOTE The coefficients in equation F.12 are from ITU-R BT.601-5. The ITU-R BT.601-5 defines Y′ of YCC to the
three decimal place accuracy. An additional decimal place is defined above to be consistent with the other matrix
coefficients defined in this standard.
And quantization for sYCC is defined as;
′
Y = round[]()WDC − KDC × Y + KDC
sYCC sYCC
′
Cb = round[]()Range × Cb + Offset (F.13)
sYCC sYCC
[]()′
Cr = round Range × Cr + Offset
sYCC sYCC
For 24-bit encoding (8-bit/channel), the relationship is defined as:
Y = round[]()255 − 0 × Y ′ + 0 = round[255 × Y ′]
sYCC sYCC sYCC
(8)
′ (F.14)
Cb = round[]()255 × Cb + 128
sYCC sYCC
(8)
′
Cr = round[]()255 × Cr + 128
sYCC sYCC
(8)
For 24-bit encoding, the sYCC values shall be limited to a range from 0 to 255 after equation
(8)
F.14.
24-bit encoding (8-bit/channel) shall be the default sYCC encoding bit depth. Other bit depths
may be unsupported in general use.
Where other N-bit/channel encoding is supported ( N > 8 ), the relationship is defined as;
N
′
Y = round[(2 −1)×Y ]
sYCC sYCC
(N)
N N −1
[]()() ′ (F.14′)
Cb = round 2 −1 × Cb + 2
sYCC sYCC
(N)
N N −1
′
Cr = round[]()()2 −1 × Cr + 2
sYCC sYCC
(N)
For N-bit/channel encoding ( N > 8), the sYCC values shall be limited to a range from 0 to
(N)
N
2 –1 after equation F.14′.
61966-2–1 Amend. 1  IEC:2003(E) – 7 –
F.4 Transformation from 8-bit sYCC values ( Y , Cb , Cr )
sYCC sYCC sYCC
(8) (8) (8)
to 8-bit sRGB values ( R , G , B )
sRGB(8) sRGB(8) sRGB(8)
Y ′ = Y 255
sYCC sYCC
(8)
′
Cb =()Cb −128 255 (F.15)
sYCC sYCC
(8)
Cr′ =()Cr −128 255
sYCC sYCC
(8)
′ ′
R 1,000 0 0,000 0 1,402 0 Y
    
sRGB sYCC
    
′ ′ (F.16)
G = 1,000 0 − 0,344 1 − 0,714 1 Cb
sRGB sYCC
    
 ′    ′ 
B 1,000 0 1,772 0 0,000 0 Cr
 sRGB   sYCC
′
R = round(255 × R )
sRGB(8) sRGB
G = round(255 × G′ ) (F.17)
sRGB(8) sRGB
′
B = round(255 × B )
sRGB(8) sRGB
NOTE Since 8 bit sYCC values are not limited by the gamut of 8 bit sRGB values, some kind of mapping is
needed for the colours that contains over-ranged non-linear floating point sR′G′B′ tristimulus values (under 0,0 or
over 1,0), when converting 8 bit sYCC to 8 bit sRGB.
F.5 Transformation from 8-bit sRGB values ( R , G , B )
sRGB(8) s
...