ISO 21727:2016
(Main)Cinematography — Method of measurement of perceived loudness of short duration motion-picture audio material
Cinematography — Method of measurement of perceived loudness of short duration motion-picture audio material
ISO 21727:2016 specifies a method of measurement of short duration motion-picture sound that allows assessment of the subjective loudness and annoyance of the sound recording when replayed at the recommended replay level in rooms aligned with the characteristics of ISO 2969. The specified method of measurement assesses the entire duration of the sound recording, typically commercials and trailers that do not exceed 3 min in length, with suitable channel summation, frequency weighting and time integration. It does not specify a maximum recommended level for such material and is solely aimed at describing a measurement method. NOTE Typical recording and replay levels are discussed in Annex A.
Cinématographie — Méthode de mesure de l'intensité sonore percue pour les films cinématographiques de courte durée
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INTERNATIONAL ISO
STANDARD 21727
Second edition
2016-05-01
Cinematography — Method of
measurement of perceived loudness of
short duration motion-picture audio
material
Cinématographie — Méthode de mesure de l’intensité sonore percue
pour les films cinématographiques de courte durée
Reference number
ISO 21727:2016(E)
©
ISO 2016
---------------------- Page: 1 ----------------------
ISO 21727:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 21727:2016(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Method of measurement . 3
4.1 General . 3
4.2 Procedure . 3
4.2.1 Input calibration and M-type frequency weighting . 3
4.2.2 Scalar channel summation . 3
4.2.3 Loudness-equivalent level . 3
4.2.4 Calculation . 4
Annex A (informative) Typical recording and replay levels . 5
Bibliography . 6
© ISO 2016 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 21727:2016(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 36, Cinematography.
This second edition cancels and replaces the first edition (ISO 21727:2004), of which it constitutes a
minor revision.
iv © ISO 2016 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 21727:2016(E)
Introduction
This International Standard is intended to be used in conjunction with the International Standards
that cover the reproduction of motion-picture sound, A-chain and B-chain, including ISO 2969 and
ISO 22234.
A recommended replay level architecture exists for most current cinema sound formats. This matches
a specific recorded modulation level with a specific sound-pressure level at the main seating position
in a room designed in accordance with ISO 2969 and ISO 22234. The noise and over-modulation points
of each sound format are positioned to allow for a wide range of signal components to be recorded and
faithfully reproduced at a valid absolute level as part of a motion-picture soundtrack.
Perhaps due to their competitive nature, many motion-picture commercials and trailers make
sustained use of the highest recording level possible for the format. Consequently, many exhibitors
now find the need to reduce the replay level to a point much lower than the recommendation. This has
caused uncertainty as to the validity of the recommended replay level, which in turn creates problems
in matching dubbing theatre sound to that expected from the average cinema.
This International Standard is intended to assist in assessing the subjective loudness of motion-picture
sound so that a better match between the sound levels of commercials, trailers and main features is
maintained, and so that confidence in the validity of the recommended replay level is re-established.
© ISO 2016 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 21727:2016(E)
Cinematography — Method of measu
...
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 21727
ISO/TC 36
Cinematography — Method of
Secretariat: ANSI
measurement of perceived loudness
Voting begins on:
20160125 of short duration motion-picture
audio material
Voting terminates on:
20160325
Cinématographie — Méthode de mesure de l’intensité sonore percue
pour les films cinématographiques de courte durée
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
ISO/FDIS 21727:2015(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO 2015
---------------------- Page: 1 ----------------------
ISO/FDIS 21727:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 21727:2015(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Method of measurement . 3
4.1 General . 3
4.2 Procedure . 3
4.2.1 Input calibration and M-type frequency weighting . 3
4.2.2 Scalar channel summation . 3
4.2.3 Loudnessequivalent level . 4
4.2.4 Calculation . 4
Annex A (informative) Typical recording and replay levels . 5
Bibliography . 6
© ISO 2015 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/FDIS 21727:2015(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and nongovernmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 36, Cinematography.
This second edition cancels and replaces the first edition (ISO 21727:2004), of which it constitutes a
minor revision.
iv © ISO 2015 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 21727:2015(E)
Introduction
This International Standard is intended to be used in conjunction with the International Standards that
cover the reproduction of motionpicture sound, Achain and Bchain, including ISO 2969 and ISO 22234.
A recommended replay level architecture exists for most current cinema sound formats. This matches
a specific recorded modulation level with a specific sound-pressure level at the main seating position
in a room designed in accordance with ISO 2969 and ISO 22234. The noise and overmodulation points
of each sound format are positioned to allow for a wide range of signal components to be recorded and
faithfully reproduced at a valid absolute level as part of a motion-picture soundtrack.
Perhaps due to their competitive nature, many motion-picture commercials and trailers make
sustained use of the highest recording level possible for the format. Consequently, many exhibitors
now find the need to reduce the replay level to a point much lower than the recommendation. This has
caused uncertainty as to the validity of the recommended replay level, which in turn creates problems
in matching dubbing theatre sound to that expected from the average cinema.
This International Standard is intended to assist in assessing the subjective loudness of motion-picture
sound so that a better match between the sound levels of commercials, trailers and main features is
maintained, and so that confidence in the validity of the recommended replay level is re-established.
© ISO 2015 – All rights reserved v
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