ISO 9642:2020

INTERNATIONAL ISO
STANDARD 9642
Second edition
2020-01
Cinematography — Time and control
code for 24, 25 and 30 frames per
second motion-picture film systems —
Specifications
Cinématographie — Code de chronométrage et de commande pour
les systèmes de films cinématographiques à 24, 25 et 30 images par
seconde — Spécifications
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Modulation method . 2
5 Code formats . 2
5.1 Type C code format. 2
5.2 Type 8 code format .10
5.3 Use of binary groups .11
5.4 Assigned and unassigned address bits .12
6 Time discrepancies and colour framing in film/video transfer .12
6.1 NTSC colour recording .12
6.2 SECAM signals .13
6.3 PAL signals .13
7 Structure of the address bits .13
8 Position of the address on motion-picture film .13
9 Addresses on motion-picture prints .13
Bibliography .15
Foreword
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electrotechnical standardization.
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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
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 36, Cinematography.
This second edition cancels and replaces the first edition (ISO 9642:1993), of which it constitutes a
minor revision. The changes compared to the previous edition are as follows:
— The title has been modified to include the word "film".
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 9642:2020(E)
Cinematography — Time and control code for 24, 25 and
30 frames per second motion-picture film systems —
Specifications
1 Scope
This document specifies digital code for mats and modulation methods for motion-picture film to
be used for timing, control, editing and synchronization purposes. This document also specifies the
relationship of the codes to the motion picture frame.
Two types of code are described in this document. The first type, Type C, is a continuous code which is
very similar to the continuous code specified in IEC 60461. This type of code can be used in situations
where the film is moving continuously at the time of both recording and reproduction.
The second type of code, Type 8, is a non-continuous, block-type code, composed of blocks of data, each
complete in itself, with gaps between the blocks. It is designed so that the code can be recorded and
played back on equipment with intermittent film motion but still be decoded with the same type of
electronic equipment used to read the Type C or continuous time code.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 2022, Information technology — Character code structure and extension techniques
ISO 4241, Cinematography — Projection film leader (time-based), trailer and cue marks — Specifications
ISO 8758, Cinematography — Photographic control and data records on 16 mm and 35 mm motion-picture
film and prints — Dimensions and location
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
real time
time elapsed during the scanning of 60 fields (or any multiple thereof) in an
ideal television system at a vertical field rate of exactly 60 fields per second
3.2
colour time
time elapsed during the scanning of 60 fields (or any multiple thereof) in a
colour television system at a vertical field rate of approximately 59,94 fields per second
4 Modulation method
The modulation method shall be such that a transition occurs at the beginning of every bit period. "One"
is represented by a second transition half a bit period after the start of the bit. "Zero" is represented
when there is no transition within the bit period.
5 Code formats
Two code formats are described: Type C and Type 8. The unique characteristics of the two code types
are described in 5.1 and 5.2 respectively. Information which applies to both code types is given in 5.3
and 5.4.
5.1 Type C code format
5.1.1 Each motion-picture frame shall be defined by a unique and complete address.
5.1.2 The frames shall be numbered successively 0 to 23, 24 or 29 inclusive, corresponding to the
frame rate being used.
5.1.3 Each address shall consist of 80 bits numbered 0 to 79 inclusive.
5.1.4 The bits shall be assigned as shown in the appropriate columns of Figure 1 and Table 1.
5.1.5 The address shall start at the clock edge before the first address bit (bit zero). The bits shall be
evenly spaced throughout the address period and they shall fully occupy the address period, which is one
frame. Consequently, the bit rate shall be 80 times the frame rate in frames per second.
5.1.6 The start of the address, i.e. the clock edge before the first bit, shall coincide with the frameline
at the beginning of the image to which the address refers. The tolerance of this location is +0 % (in the
direction of film travel) and −50 % of a frame length (in the other direction). Thus, the start of the address
can lie anywhere in the top half of the frame with the preferred position at the frameline. See Figure 2.
Table 1 — Bit assignment
Bit number Bit description
Type C code Type 8 code
a
0-7 Alternating zero, one pattern
a
8-23 Synchronizing word
a
8-9 Fixed zero
a
10-21 Fixed one
a
22 Fixed zero
a
23 Fixed one
0-3 24-27 Units of frame
4-7 28-31 First binary group
8-9 32-33 Tens of frames
10 34 Drop frame flag (see 5.4)
11 35 Colour frame flag (see 5.4)
12-15 36-39 Second binary group
16-19 40-43 Units of seconds
20-23 44-47 Third binary group
a
These bits do not exist in the Type C code.
2 © ISO 2020 – All rights reserved

Table 1 (continued)
Bit number Bit description
Type C code Type 8 code
...