ISO 22077-1:2015

INTERNATIONAL ISO
STANDARD 22077-1
First edition
2015-04-01
Health informatics — Medical
waveform format —
Part 1:
Encoding rules
Informatique de santé — Format de la forme d’onde médicale —
Partie 1: Règles d’encodage
Reference number
©
ISO 2015
© ISO 2015
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
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Abbreviated terms . 1
4 Basic specifications . 2
4.1 Basic attributes . 2
4.1.1 General. 2
4.1.2 Sampling attributes . 2
4.1.3 Frame attributes . 3
4.2 Encoding rule . 4
4.2.1 General. 4
4.2.2 Tag (T) . 4
4.2.3 Data length (L) . 5
4.2.4 Value (V) . 6
4.3 Encoding principle . 6
4.3.1 General. 6
4.3.2 Definition levels . 6
4.3.3 General principles in interpretation, scope and priority of definitions . 6
5 Basic rules (Level 1) . 8
5.1 Primary description. 8
5.1.1 Sampling attributes . 8
5.1.2 Frame attributes . 9
5.1.3 Waveform .10
5.1.4 Channel .13
5.2 Auxiliary rule .14
5.2.1 Data description .14
5.2.2 Other definition .16
5.2.3 Information description .17
6 Supplemental description (Level 2) .22
7 Extended description (Level 3) .24
Annex A (informative) MFER conformance statement .27
Annex B (informative) Description example .29
Annex C (informative) Event information description .36
Annex D (informative) Example of standard encoding.38
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 215, Health Informatics.
iv © ISO 2015 – All rights reserved

Introduction
Medical waveform data such as an electrocardiogram (ECG) or an electroencephalogram (EEG) are
widely utilized in physiological examinations, physiological research, electronic medical records,
healthcare information, and other areas in the clinical field. Medical waveform data can be used for
many medical and research purposes if digital signal processing technology is applied to standardize
the data in a digital format. For medical waveforms, it is essential to standardize the data format to
expedite the mutual application of the standard so that the data can be processed electronically and
used in a variety of ways.
Simple and easy implementation: application of medical waveform format encoding rules (MFER)
is very simple and is designed to facilitate understanding, easy installation, trouble-shooting, and low
implementation cost.
Harmonization with other standards: MFER is specially utilized to describe the medical waveform
data. Other information than waveform data, such as patient demographic data and finding information,
etc. should be written using other healthcare standards, such as HL7, DICOM, ISO/IEEE 11073.
In addition, experts in each field should independently develop relevant standards for medical
specifications; for example MFER for ECG is developed by cardiologists and EEG is developed by
neurologists.
Combination with coded information and text information: MFER policy is that both machine and
human readable manner are used. Namely coded information is for computer processable and text data
are for human readable information. Arterial blood pressure (ART) is coded as 129 and information
description fields indicate “Right radial artery pressure”, for example. As the description of MFER is quite
flexible, MFER neither hinders the features of each system nor impedes the development of technologies.
INTERNATIONAL STANDARD ISO 22077-1:2015(E)
Health informatics — Medical waveform format —
Part 1:
Encoding rules
1 Scope
This International Standard specifies how medical waveforms, such as electrocardiogram,
electroencephalogram, spirometry waveform, etc., are described for interoperability among healthcare
information systems.
This International Standard may be used with other relevant protocols, such as HL7, DICOM,
ISO/IEEE 11073, and database management systems for each purpose.
This is a general specification, so specifications for particular waveform types and for harmonization
with DICOM, SCP-ECG, X73, etc. are not given.
This International Standard does not include lower layer protocols for message exchange. For
example, a critical real-time application like a patient monitoring system is out of scope and this is an
implementation issue.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
frame
waveform encoding unit consisting of data blocks, channels, and sequences
2.2
medical waveform
time sequential data that are sampled by A/D converter or transmitted from medical equipment
2.3
sampling
data that are converted at a fixed time interval
2.4
channel
individual waveform data group
3 Abbreviated terms
AAMI Association for the Advancement of Medical Instrumentation
A/D Analog to Digital
CSE Common Standards for Quantitative Electrocardiography
CEN Comité Européen de Normalization/European Committee for Standardization
ECG Electrocardiogram
EEG Electroencephalogram
GPS Global Positioning System
HL7 Health Level Seven
DICOM Digital Imaging and Communications in Medicine
IEEE Institute of Electrical and Electronic Engineers
IEC International Electrotechnical Commission
JIS Japanese Industrial Standard
LSB Least significant bit
MFER Medical waveform Format Encoding Rules
MSB Most significant bit
OID Reference to the ISO standard.
SCP-ECG Standard Communications Protocol for Computerized Electrocardiography (EN 1064)
SPO Saturation of Peripheral Oxygen
UID Reference to the ISO standard
UUID Reference to the ISO standard
VCG Vectorcardiogram
4 Basic specifications
4.1 Basic attributes
4.1.1 General
Medical waveform data described in accordance with the MFER consists of Sampling attributes
(Figure 1), Frame attributes (Figure 2) and other supplemental information.
4.1.2 Sampling attributes
Sampling information has two attributes, sampling rate and sampling resolution.
a) sampling rate
The sampling rate is described with sampling interval or sampling frequency. The sampling interval
stands for the time or distance interval of each sampled data as distributed sampled waveform data.
b) sampling resolution
Sampling resolution represents a minimum sampling value per least significant bit (LSB).
2 © ISO 2015 – All rights reserved

Key
T sampling interval (or frequency)
R resolution
Figure 1 — Sampling attributes
4.1.3 Frame attributes
The frame is a waveform encoding unit consisting of data blocks, channels, and sequences. A configuration
example of a frame is shown as Figure 2.
a) data block
The data block is the waveform data array for each channel.
b) channels
The channels indicate different waveform groups, e.g. if three waveform groups exist, the number of
channels is three.
c) sequence
The sequence represents the repetition of the group with the data block and channel.
Key
1 frame
2 data block
3 channel
4 sequence
Figure 2 — Frame attributes
4.2 Encoding rule
4.2.1 General
The header and waveform data should be encoded based on the encoding rules which are composed of
the tag, length and value (TLV), as shown in Figure 3.
Tag (T)Data length (L)Value (V)
Figure 3 — Data unit
— The tag (T) consists of one or more octets and indicates the attribute of the data value.
— The data length (L) is the length of data values indicated in one or more octets.
— The value (V) are the contents which are indicated by tag (T); e.g. attribute definition, waveform
data, etc.
4.2.2 Tag (T)
The tag is composed of a class, primitive/context (P/C) and tag number. The tag is classified into four
classes (Table 1). Classes 0 to 2 are MFER standard coding and class 3 is for private use. The private
definition is intended for special purposes but should be included within any updated future version.
4 © ISO 2015 – All rights reserved

Table 1 — Tag
8 7 6 5 4 3 2 1
Class P/C Tag number
0 0
0 1 MFER
0/1
1 0
1 1 Private
a) primitive type (P/C = 0).
P/C = 0 indicates a primitive description.
b) context type (P/C = 1).
This has only two tags which are group and channel definition on current MFER. Figure 4 gives an
example of a group definition.
876 5432 1
01 0011 1
Figure 4 — Group definition
4.2.3 Data length (L)
The data length indicates the number of octets used for data values in the value (V) section (i.e. the
length excluding octets used for tag and data length sections). The data length encoding method differs
depending on whether the number of octets used for data are less than 127 or more than 128 octets.
a) In case the data value section uses 127 octets or less.
The length is encoded in one octet, as shown in Figure 5.
876 5432 1
0Data length
Figure 5 — Data length ≤ 127 octets
b) In case the data value section uses 128 octets or more.
The long data length can be encoded using multiple octets. The first octet indicates the number of octets
used to represent the total data length. For example, two subsequent octets are used to indicate the
waveform data length from 128 to 65 535 and thus three octets are used to encode the data length as in
Figure 6. However, MFER allows representation of a data length using multiple octets even if the length is
less than 127 octets. For example, four octets can describe up to 4 294 967 295 bytes length as a data part.
87 654 32 187 65 43 218 76 543 21 87 654 32 1
Length number
1 Most signiicant octetThe second octetThe third octet
(e.g. 3octets)
Figure 6 — Data length
c) Designation of indefinite data length.
MFER allows designation of an indefinite data length by encoding 80 h on the top of the data length field
(Figure 7). This indefinite length designation is terminated by encoding the end-of-contents (tag = 00,
data length = 00).
Tag Length End-of-Contents
----- ----- -----
P/C=1 (80h) (00,00)
Figure 7 — Indefinite length designation and end-of-contents designation
d) In case the data length is 0.
MFER indicates that the definition indicated by tag resets to the default value. Namely, on the root
definition the concerned items re-initialize to default values and in case of the channel definition, the
channel definition is re-initialized to the root definition.
4.2.4 Value (V)
The header or waveform data values are encoded in the value section according to descriptors
specified by the tag.
4.3 Encoding principle
4.3.1 General
All definitions in MFER have default values, so any additional or amended definitions are optional. Thus
the definition corresponding to each tag has a default value, so re-definition is not necessary if the
default value is retained. It is expected that default definitions will suffice for most purposes.
4.3.2 Definition levels
4.3.2.1 Level 1 — basic definitions
Definitions at level 1 are basic definitions, which are ordinary rules (marked with an asterisk) and
ensure precise encoding.
4.3.2.2 Level 2 — supplementary definitions
Definitions at level 2 are supplementary definitions. They may be used as required but it is desirable
to associate the supplementary definitions with a host protocol where they can be defined with the
host protocol.
4.3.2.3 Level 3 — extended definitions
Definitions at level 3 are extended definitions, which should be used as little as possible. Items of these
extended definitions may considerably affect the system with regard to security. Thus, great care should
be taken in using them.
4.3.3 General principles in interpretation, scope and priority of definitions
4.3.3.1 Initial values (default value)
All definitions in MFER have initial values that are applied until redefined by any subsequent definition.
6 © ISO 2015 – All rights reserved

4.3.3.2 Multiple definitions
Multiple definitions may be made for any item. Depending on items, a new definition, an old definition,
or all definitions (such as for events), can be used multiple times.
For example, setting the sampling frequency to 250 Hz overrides the initial value of 1 kHz.
If multiple events occur, they are interpreted in definition order.
4.3.3.3 Later definition priority
Each definition is interpreted in definition order. If an item has related definitions, definition should be
made in due order. The default endianity is big-endian, so to use little-endian endianity the definition for
little-endian must be designated.
For example, before defining each channel, the number of channels should be defined.
4.3.3.4 Channel attributes definition order
Before defining the attributes of a channel, the number of channels should be defined. If the number of
channels is defined later, previous channel definitions are reset to the root definition including default values.
4.3.3.5 Root definition (general definition) and channel definition (definition per channel)
The root definition is effective for all channels. The channel definition is effective only for the relevant
channel and overrides the root definition. However, care should be taken because if a subsequent change
to the root definition is made, it will override the default content of the relevant channel for subsequent
channel definitions.
For example, if EEG is designated in the root definition, ECG designated for a channel in the channel
definition overrides EEG.
4.3.3.6 Definition reset
If the data length is defined as zero (no data) in the definition of an item, the content in the definition
is reset to default value. If the data length is designated as zero in a channel definition, the definition
follows the root definition including the default value. If the number of channels is defined, contents
defined for the channel attribute are all reset to the root definition including the default value.
4.3.3.7 Incomplete definition ignored
If a definition is made without an adequate preceding definition, the definition is ignored.
In the absence of any complete definition, the default root definition will be applied.
For example, if the number of channels is undefined, any dependent channel definition is ignored.
4.3.3.8 Succession of definitions
Unless redefined, each definition applies to all succeeding frames, in the effective range, except for the
data pointer which is succeeding renewed. Thus, contents defined in the root definition apply to all frames
unless overridden by channel definition(s), so it suffices to define common items in the root definition.
For example, to use little-endian for all encodings with MFER, define little-endian once, then it is effective
over the whole region irrespective of frames.
4.3.3.9 Definition and efficacy of data
It depends on the functional capability of the user application whether or not the user can use data
defined by the provider. If some content cannot be processed, users may discard all the data or use only
the processable range of data.
5 Basic rules (Level 1)
5.1 Primary description
5.1.1 Sampling attributes
Sampling attributes are sampling frequency or sampling interval and resolution are given in Tables 2 to 5.
a) MWF_IVL (0Bh): Sampling rate
This tag indicates the frequency or interval the medical waveform is sampled (Table 2).
Table 2 — Sampling rate
Data Encoding range/ Duplicated defini-
MWF_IVL* Default
length remarks tions
Unit 1 —
th −128 +127
Exponent (10 power) 1 10 to 10
11 0Bh 1 000 Hz Override
e.g. unsigned 16-bit
Mantissa ≤4
integer
The unit may be frequency in Hertz, time in seconds or distance metres (Table 3).
Table 3 — Sampling rate unit
Unit Value Remarks
Frequency Hz 0 Including power
Time interval s 1 —
Distance m 2 —
b) MWF_SEN (0Ch): Sampling resolution
This tag indicates the resolution, minimum bits, the medical waveform is sampled (generally,
digitized) (Table 4).
Table 4 — Sampling resolution
Data Encoding range/ Duplicated defini-
MWF_SEN* Default
length remarks tions
Unit 1 —
th −128 +127
Exponent (10 power) 1 10 to 10
12 0Ch see Table 5 Override
e.g. unsigned 16-bit
Mantissa ≤4
integer
8 © ISO 2015 – All rights reserved

Table 5 — Sampling resolution units
Unit Value Default Remarks
Voltage V 0 0,000 001 V —
mm Hg(Torr) 1 — —
Pa 2 — —
Pressure
cm H O 3 — —
mm Hg/s 4 — —
dyne 5 — —
Force
N 6 — —
Ratio % 7 — Include volume fraction (%)
Temperature °C 8 — —
−1
min 9 — —
Heart rate
−1
s 10 — —
Resistance Ω 11 — —
Current A 12 — —
Rotation r/min 13 — —
W 14 — —
Power
dB 15 — —
Mass kg 16 — —
Work J 17 — —
−2 −5
Vascular resistance dyne ⋅ s ⋅ m cm 18 — —
l 19 — —
Flow rate, flow, volume l/s 20 — —
l/min 21 — —
Luminous intensity cd 22 — —
5.1.2 Frame attributes
As described in Figure 2 a frame is composed of data blocks, channels and sequences.
a) MWF_BLK (04h): Data block length
This tag indicates the number of data sampled in a block (Table 6).
Table 6 — Data block length
MWF_BLK* Data length Default Remarks Duplicated definitions
04 04h ≤ 4 1 — Override
b) MWF_CHN (05h): Number of channels
This tag indicates the number of channels (Table 7). As the previously specified channel attribute is
reset to the root definition including default, the number of channels should be specified before each
definition of the channel attribute. The number of channels cannot be specified with a channel definition
of channel attribute.
Table 7 — Number of channels
MWF_CHN* Data length Default Remarks Duplicated definitions
05 05h ≤4 1 — Override
c) MWF_SEQ (06h): Number of sequences
This tag indicates the number of sequences (Table 8). If the number of sequences is not designated, it
depends on the data block length, the number of channels and the number of waveform data values
which are defined for the concerned frame.
Table 8 — Number of sequences
MWF_SEQ* Data length Default Remarks Duplicated definitions
Depends on waveform data
06 06h ≤ 4 — Override
length
5.1.3 Waveform
The waveform type, waveform attributes, and waveform data are encoded as follows.
a) MWF_WFM (08h): Waveform class
Waveforms such as standard 12-lead ECG and monitoring ECG are grouped based on instruments and
purposes, as shown in Table 9.
Table 9 — Waveform class
MWF_WFM* Data length Default Remarks Duplicated definitions
2 Non-specific waveform —
08 08h Override
Str ≤ 32 Waveform description —
As a general rule, standardization will be made by type of waveforms, each is described in a separate
specification (e.g. for standard 12-lead ECG 11073-92301). However, because monitoring systems
use multiple waveforms such as ECG, SpO2, EEG, etc., refer to the specification for each individual
waveform standard.
For types of waveform (Table 10), numbers 1 to 49 151 (BFFFh) are already reserved. Numbers 49 152
to 65 535 can be used privately but it should be documented in the MFER specification as quickly as
possible if the waveform is commonly used.
b) MWF_LDN (09h): Waveform attributes (lead name, etc.)
Code and information can be added to the type of waveform. If a waveform is required to be reconfigured,
as in the case of deriving leads III and aVF from leads I and II, the codes should always be specified. The
codes should be taken into special consideration as they have a function to specify some processing,
as in the case of deriving other limb leads from leads I and II or deriving a waveform based on the lead
name. See Table 11 for the definition of waveform attributes.
As the lead names are defined depending on the class of waveform, they are not consolidated throughout
each class of waveform in MFER. Thus, caution should be taken in encoding lead names.
For waveform codes, numbers 1 to 49 151 (BFFFh) are already reserved. Numbers 49 152 to 65 535 can
be used privately but should be used for new types of waveforms by upgrading the MFER promptly.
10 © ISO 2015 – All rights reserved

Table 10 — Classification of waveforms
Classification Type Value Description Remarks
— — 0 Unidentified —
Different kinds of 12 lead
ECG_STD12 1 Standard 12 lead ECG ECGs including general ECGs
can be encoded
ECG_LTERM 2 Long-term ECG Holter ECG, monitoring ECG
ECG_VECTR 3 Vectorcardiogram —
ECG_EXCER 4 Stress ECG —
His bundle ECG, intracardiac
ECG_INTR 5 Intracardiac ECG ECG, intravascular ECG, car-
Electrocardiogram
diac surface ECG
Body surface potential map
ECG_SURF 6 Body surface ECG
Body surface
His bundle ECG
Ventricular late poten-
ECG_ILATE 7 —
tial
Body surface late poten-
ECG_LATE 8 —
tial
Sound SOUND 30 PCG, etc. 8 kHz, 11 kHz, 22 kHz, etc.
Fingertip pulse, carotid
Pulse PULSE 31 —
pulse
MON_LTRM 20 Long-term waveform —
MON_SPL 21 Sampled waveform —
Monitoring
MON_PWR 25 Power spectrum Some part is EEG_CSA
MON_TRD 26 Trendgram —
Magnetocardiogram 100 MCG —
Includes surgical monitoring
EEG_REST 40 Resting EEG
EEG
ABR
EEG_EP 41 Evoked EEG
Electroencephalogram
SEP
EEG_CSA 42 Frequency analysis —
EEG_LTRM 43 Long-term EEG Sleeping EEG
Private 49 152 to 65 535 — —
Table 11 — Definition of waveform attributes
Data Duplicated defini-
MWF_LDN* Default Data range, remarks
length tions
Data length = 2, if wave-
Waveform code 2 form information is
Unidenti-
encoded
09 09h Override
fied
Waveform informa-
Str ≤ 32 —
tion
EXAMPLE Standard 12-lead ECG code, shown in Table 12.
Mainly, standard 12-leads are encoded according to the SCP-ECG (EN 1064) or annotated ECG coding
system, but some leads are not defined the same as SCP-ECG.
Table 12 — Lead code of standard 12 lead ECG
Code Lead Code Lead
1 I 13 V5R
2 II 14 V6R
3 V1 15 V7R
4 V2 61 III
5 V3 62 aVR
6 V4 63 aVL
7 V5 64 aVF
8 V6 66 V8
9 V7 67 V9
11 V3R 68 V8R
12 V4R 69 V9R
EXAMPLE Monitoring aortic pressure waveform.
Encoding monitoring waveform information.
Table 13 — Blood pressure waveform (Aortic blood pressure waveform)
Waveform code Waveform information Remarks
128 — Coded value indicates as “Aortic pressure”
Coded value indicates as “Arterial pressure” and Informa-
129 “Aorta”
tion description part indicates “Aorta”
Coded value only indicates as “Pressure” and Information
143 “Aorta”
description part indicates “Aorta”
EXAMPLE Electroencephalogram waveform.
Generation of waveform codes by combination of electrodes (see Figure 8).
16 15 14 13 12 11 10 98 765 432 1
01 − negative electrode (G1) + positive electrode (G2)
Figure 8 — Generation of waveform code by combination of electrodes
Waveform codes can be generated by combination of electrode codes, as shown in Table 14 and Table 15.
Table 14 — Electrode code
Name Abbreviation Electrode code
Left front polar FP1 12
Right front polar FP2 13
Left ear A1 74
Right ear A2 75
12 © ISO 2015 – All rights reserved

Table 15 — Example of waveform code generation
Lead − electrode + electrode Waveform code
FP1 - A1 12 74 17994(464A)
FP2 - A2 13 75 18123(46CB)
c) MWF_WAV (1Eh): Waveform data
The entity of waveform data should strictly be aligned as defined in Frame attributes (4.1.3). If the
waveform data are compressed, the data alignment may depend on the compression method, but the
waveform data after un-compressing should be aligned according to the definition (see Table 16).
If waveform data are different from what is defined in frame information, exceeding data may be
discarded. However, such processing depends on application and it is not guaranteed.
Table 16 — Waveform body
MWF_WAV Data length Default Remarks Duplicated definitions
30 1Eh waveform Waveform length — — —
5.1.4 Channel
a) MWF_ATT (3Fh): Channel attributes (channel definition)
This tag defines the attributes of each channel (see Table 17). Before this definition, it should be required
to specify the channel number using Table 7.
The method of encoding a channel number differs depending on whether it is ≤127 or ≥128. Refer to
Figure 10 for ≤127 and to Figure 11 for ≥128.
Table 17 — Channel attributes
MWF_ATT* Data length Default Remarks Duplicated definitions
63 3Fh Depends on definition — — Override
NOTE Channel definition for each channel is encoded with a special context tag of P/C = 1 and tag number of
1Fh. That is, the type number is P/C + tag number encoded with 3Fh and identifies the attribute of the relevant
channel. The channel number is identified with seven bits in the octet with bit 8 = 0 for up to 127 channels and
with bit 8 = 1 for 128 or higher channel number.
For the tag of the channel attribute definition, context mode is selected with P/C (bit 6 = 1).
87 654 32 1
1 31(1Fh)
00 0Channel number
63(3Fh)
Figure 9 — Number of channel ≤127
87 654 321 88 8
1 31(1Fh)
Channel number 1 Channel number N
00 1 1 ------ 0
(higher) (lowest)
63(3Fh)
Figure 10 — Number of channel ≥128
The data length includes all the range of the channel attribute definition (Figure 11).
TagData lengthGroup of deinition
Channel attribute Channel attribute Channel attribute
----
Channel
deinition deinition deinition
3Fh All deinition
number
TL VT LV —T LV
Figure 11 — Definition of channel attributes
The indefinite length described in Figure 7 can be used for the channel attribute definition
(Figures 11 and 12).
TagData lengthGroup of deinition
Channel attribute Channel attribute
----- End-of-contents
Channel
deinition deinition
3Fh 80h
number
TL VT LV —0000
Figure 12 — Definition of channel attributes with indefinite length
5.2 Auxiliary rule
5.2.1 Data description
a) MWF_DTP (01h): Data type
This tag indicates the type of waveform data (Tables 18 and 19). While medical waveforms are usually
sampled with a precision of 12 bits, by default they are all interpreted and encoded as 16-bit data.
Table 18 — Data type
Duplicated defini-
MWF_DTP Data length Default Remarks
tions
10 0Ah 1 Signed 16-bit integer — Override
Table 19 — Data type code
Value Type of data
0 Signed 16 bits integer, −32 768 to 32 767
1 Unsigned 16 bits integer, 0 to 65 535
2 Signed 32 bits integer
3 Unsigned 8 bits integer
4 16 bits status
5 Signed 8 bits integer
6 Unsigned 32 bits integer
7 32 bits single-precision floating (IEEE 754)
8 64 bits double-precision floating (IEEE 754)
14 © ISO 2015 – All rights reserved

Table 19 (continued)
Value Type of data
9 8 bits AHA differential
Note “8 bit AHA differential allows large values to be expressed in just 8 bits because each succeeding value
expresses the difference from the previous value.
b) MWF_OFF (0Dh): Offset value
This tag indicates an offset value (Table 20) of sampling data. Encoding of an offset value depends on the
type of encoding data.
Table 20 — Offset value
Duplicated defini-
MWF_OFF Data length Default Remarks
tions
≤8 (depends on types of
13 0Dh 0 — Override
encoding data values)
c) MWF_NUL(12h): NULL value
This tag indicates null data. If null values (Table 21) are included in waveform data, the waveform datum
is ignored even if it exists. As null data use the same encoding space as waveform data, the tag should
be used carefully. For example, a minimum negative value 8 000 h is occasionally used for a null value.
If the null values are encoded during a period in which the electrode is removed, ECG is not displayed.
Encoding of a null value depends on the type of encoding data.
Table 21 — Null value
Duplicated defini-
MWF_NUL Data length Default Remarks
tions
≤8 (depends on types of
18 12h Unused — Override
encoding data values)
d) MWF_CMP (0Eh): Compression
This tag is to compress the encoding waveform.
Table 22 — Compression
Duplicated defini-
MWF_CMP Data length Default Remarks
tions
Compression
code
Data before compres-
14 0Eh Data length 4
sion
Compressed Data length after
Compressed data
data compression
MFER enables encoding of waveforms by compressing (Table 22). This improves the efficiency of
encoding capacity but makes the processing speed decrease, so sufficient consideration should be made
when compressing. If compression is specified with this tag (MWF_CMP), data in the header section or
waveforms in the data section are all compressed thereafter. Compressed data block length and channels
in sequences may not be available depending on compression methods (Table 23) but the encoded frame
information returns after decompression.
Table 23 — Compression method
Compression ID Compression method Description
0 No compression No compression applied to data encoding (default)
2 Compression applied to header section
MFER
3 Compression applied to waveform data section
Compressed data methods for headers and waveforms are given in Tables 24 and 25 respectively.
Table 24 — Compression applied to header section
Tag 0Eh
Data length Length of whole data section
Compression code 2
Data before compression Length of data before compression
Compressed data (header) Compressed data (data of header)
Table 25 — Compression applied to waveform data
Tag 0Eh
Data length Length of whole data section
Compression code 3
Data before compression Length of data before compression
Compressed data (waveform data) Compressed data waveform data
5.2.2 Other definition
a) MWF_BLE (01h): Endianity
This tag indicates byte alignment in the data section (TLV values only). The big-endian is aligned byte
1)
1)
data from most significant to least significant. This is used by Sun Microsystems® and Macintosh®
1)
CPUs. The little-endian is aligned from least significant to most significant. This is used by Intel® and
other ‘PC’ CPUs (see Tables 26 and 27).
Table 26 — Endianity
Duplicated defini-
MWF_BLE Data length Default Remarks
tions
01 01h 1 Big-endian — Override
Table 27 — Big/Little endian
Endianity
0 Big-endian
1 Little-endian
However, irrespective of the specification by this tag, the tag, and data length field are processed in the
network alignment (big-endian).
b) MWF_PNT (07h): Pointer
1) Sun Microsystems®, Macintosh®, and Intel® are examples of suitable products available commercially. This
information is given for the convenience of users of this document and does not constitute an endorsement by ISO
of these products.
16 © ISO 2015 – All rights reserved

This tag indicates the waveform data pointer, which is represented by the sampling rate of the root level,
in the frame. If no pointer is designated, the pointer of the first frame is initialized as zero (Table 28).
The pointer for the next frame is deemed to be a value adding the number of data length of the virtual
root level channel in the previous frame.
For example, if no pointer is specified for the first frame with the sampling interval set at 2 ms, and
the number of waveform length for each channel set at 1 000, and the number of sequences set at 1 in
the root definition, then the initial pointer of the second frame advances by 2 s (1 000 data values × 1
sequence of 2 ms).
Table 28 — Pointer
Duplicated defini-
MWF_PNT Data length Default Remarks
tions
Zero or pointer of previous
07 07h ≤4 — Override
frame
c) MWF_ZRO (00h): Blank/End-of-contents
Usually, a blank tag is not analysed. This tag also indicates the end of the indefinite length if designated,
together with data length = 0. End-of-contents (Table 29) need succeed two zero as explained in Figure 7.
Table 29 — Blank or end-of-contents
MWF_ZRO Data length Default Remarks Duplicated definitions
00 00h 1 — — Multiple use possible
5.2.3 Information description
a) MWF_PRE (40h): Preamble
This tag for a special purpose is encoded at the heading of a file to indicate the attributes of the entire
MFER waveform file and data. The MWF_PRE is fixed in length. The classification is in four characters
(MFR +space) and description is in a fixed number of 28 characters. Blank fields, if any, are to be filled
with 00h or space (20h; see Table 30).
Table 30 — Preamble
MWF_PRE Data length Default Remarks Duplicated definitions
4 “MFR“
64 40h — To be encoded at the head
28 28 characters
EXAMPLE Preamble information:
“MWF_PRE 0x20 MFR Standard 12 leads ECG” is equal to “@ MFR Standard12 leads ECG”.
b) MWF_MAN (17h): Manufacturer information of medical device
This tag indicates the information on the manufacturer, model and version number of the medical
waveform generating machine with a component separator in between (see Table 31).
Table 31 — Manufacturer information
MWF_MAN Data length Default Remarks Duplicated definitions
23 17h Str ≤ 128 none — Override
EXAMPLE Description sample:
Manufacturer^model^version number^serial number.
c) MWF_EVT (41): Event
This tag is to encode supplementary waveform information such as events (refer to Annex C; see Table 32).
— Beat annotation: for classification of waveforms, etc.
— Interpretation: for interpretation of relevant waveform.
Table 32 — Event
Data Encoding range/ Duplicated defini-
MWF_EVT Default
length remarks tions
event code 2
Starting time Number of data values
(point) acquired at the sampling
65 41h None Possible
interval defined in the
Duration 4
root definition
Event information Str < 256
d) MWF_INF (15h): Waveform information
This tag indicates waveform information which is generated (refer to Annex C), for example, catheter
information to measure cardiac output by dye dilution method (see Table 33).
Table 33 — Waveform information
Data Duplicated defini-
MWF_INF Default Data range/remarks
length tions
Information code 2 — —
Starting time Point number based on
(point) the sampling interval
21 15h specified in the root defi- Possible
Duration 4
nition
Waveform informa-
Str < 256 —
tion
e) MWF_CND (44h): Acquisition or processing information
This tag represents the acquisition condition or processing information during the waveform acquisition
processing. For example, if the EEG waveforms are stored in original form but displayed with a
montage during examination, the montage is represented with this tag to reproduce the integrity with
combination electrodes (see Table 34).
18 © ISO 2015 – All rights reserved

Table 34 — Recording/Display condition
Data Duplicated defini-
MWF_CND Default Remarks
length tions
Acquisition condi- — — —
tion
Description code 1 2
Description code 2 2
68 44h
Starting point 4
Duration 4
Descriptive informa-
Str < 256
tion
MFER requires faithful reproduction of waveforms. For example, the waveform was displayed during
measurement using some filters, but the waveform in MFER coding is stored in unprocessed form as
far as possible and filter or montage information are described in this tag. The contents for expected
faithful reproduction are encoded with description codes 1 and 2. The conditions are provided in the
waveform specifications (Part 3).
f) MWF_NTE (16h): Comment
This tag represents a memo or comment. It does not directly affect encoding of waveforms.
Information affecting waveforms is encoded using the MWF_INF tag (waveform information).
Table 35 — Comment
MWF_NTE Data length Default Remarks Duplicated definitions
22 16h Str < 256 — — Possible
A comment should be encoded within 255 characters but multiple comments may be written as required.
Whether a comment has meaning or not depends on the user’s system. A long comment can be written
by using this tag the required number of times.
By usi
...