ISO 22077-1:2022

INTERNATIONAL ISO
STANDARD 22077-1
Second edition
2022-01
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 2022
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 2
4 Basic specifications .2
4.1 Basic attributes . 2
4.1.1 General . 2
4.1.2 Sampling attributes . 3
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) .21
7 Extended description (Level 3) .24
Annex A (informative) MFER conformance statement .27
Annex B (informative) Description example .28
Annex C (informative) Event information description .35
Annex D (informative) Example of standard encoding.36
Bibliography .41
iii
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
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on the ISO list of patent declarations received (see www.iso.org/patents).
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For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 215, Health informatics.
This second edition cancels and replaces the first edition (ISO 22077-1:2015) of which it constitutes a
minor revision. The changes are as follows:
— some typographical errors have been corrected;
— Clause 2 “Normative references” has been added;
— Note 1 to entry has been added to terminology entries 3.1.1, 3.1.3 and 3.1.4, and terminology entry
3.1.5 has been added;
— classifications and types of waveform in Table 10 have been added;
— the character code in Table 39 has been changed;
— a Bibliography has been added.
A list of all parts in the ISO 22077 series can be found on the ISO website.
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
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: the application of medical waveform format encoding rules (MFER)
is very simple and is designed to facilitate understanding, easy installation, troubleshooting and low
implementation cost.
Harmonization with other standards: MFER are specially utilized to describe the medical waveform
data. Other information than waveform data, such as patient demographic data and finding information,
1)
etc., should be written using other healthcare standards, e.g. HL7, DICOM® , the ISO/IEEE 11073 series.
In addition, experts in each field should independently develop relevant standards for medical
specifications, e.g. 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. For example, arterial blood pressure (ART) is coded as 129
and information description fields indicate “right radial artery pressure”. As the description of MFER
is quite flexible, MFER neither hinders the features of each system nor impedes the development of
technologies.
1)  DICOM is the trademark of a product supplied by Medical Imaging & Technology Alliance, a division of the
National Electrical Manufacturers Association. This information is given for the convenience of users of this
document and does not constitute an endorsement by ISO of the product named.
v
INTERNATIONAL STANDARD ISO 22077-1:2022(E)
Health informatics — Medical waveform format —
Part 1:
Encoding rules
1 Scope
This document specifies how medical waveforms, such as electrocardiogram, electroencephalogram,
spirometry waveform, etc., are described for interoperability among healthcare information systems.
This document can be used with other relevant protocols, such as HL7, DICOM®, the ISO/IEEE 11073
series, 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 document does not include lower layer protocols for message exchange. For example, a critical
real-time application such as a patient monitoring system is out of scope and this is an implementation
issue.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
frame
waveform (3.1.5) encoding unit consisting of data blocks, channels (3.1.4) and sequences
Note 1 to entry: The frame in this document is the same as waveform frame.
3.1.2
medical waveform
time sequential data that are sampled by an A/D converter or transmitted from medical equipment
3.1.3
sampling
data that are converted at a fixed time interval
Note 1 to entry: The sampling in this document is the same as waveform sampling.
3.1.4
channel
individual waveform (3.1.5) data group
Note 1 to entry: The channel in this document is the same as waveform channel.
3.1.5
waveform
graph showing a change in some physical quantity with time
3.2 Abbreviated terms
A/D analogue to digital
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
OID object identifier
SCP-ECG Standard Communications Protocol for Computerized Electrocardiography (see EN 1064)
SpO saturation of peripheral oxygen
UID unique identifier
UUID universally unique identifier
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 (see
Figure 1), frame attributes (see Figure 2) and other supplemental information.
4.1.2 Sampling attributes
Sampling information has two attributes: sampling rate and sampling resolution.
a) 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 represents a minimum sampling value per least significant bit (LSB).
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 in Figure 2.
a) The data block is the waveform data array for each channel.
b) The channels indicate different waveform groups, e.g. if three waveform groups exist, the number
of channels is three.
c) 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.
— 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) is the contents which are indicated by tag (T), e.g. attribute definition, waveform data.
Figure 3 — Data unit
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 (see 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.
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.
Figure 4 — Group definition
4.2.3 Data length (L)
4.2.3.1 General
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.
4.2.3.2 When the data value section uses 127 octets or less
The length is encoded in one octet, as shown in Figure 5.
Figure 5 — Data length ≤ 127 octets
4.2.3.3 When 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 shown in Figure 6. However, MFER allow representation of a data length using multiple octets even if
the length is less than or equal to 127 octets. For example, four octets can describe up to 4 294 967 295
bytes length as a data part.
Figure 6 — Data length
4.2.3.4 Designation of indefinite data length
MFER allow designation of an indefinite data length by encoding 80 h on the top of the data length field
(see Figure 7). The indefinite data length is valid only when the waveform data value is described at
the end of the file. This indefinite length designation is terminated by encoding the end-of-contents
(tag = 00, data length = 00).
Figure 7 — Indefinite length designation and end-of-contents designation
4.2.3.5 When the data length is 0
“Data length 0” 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 cases 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 can considerably affect the system with regard to security. Thus, great care should
be taken when 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.
4.3.3.2 Multiple definitions
Multiple definitions may be made for any item. Depending on the 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
5.1.1.1 General
Sampling attributes are sampling frequency or sampling interval and resolutions are given in Tables 2
to 5.
5.1.1.2 MWF_IVL (0Bh): Sampling rate
This tag indicates the frequency or interval the medical waveform is sampled (see Table 2).
Table 2 — Sampling rate
MWF_IVL* Data Default Encoding range/ Duplicated
length remarks definitions
Unit 1 —
th −128 +127
Exponent (10 power) 1 10 to 10
11 0Bh 1 000 Hz Override
Mantissa ≤ 4 e.g. unsigned 16-bit
integer
The unit may be frequency in Hertz, time in seconds or distance in meters (see Table 3).
Table 3 — Sampling rate unit
Unit Value Remarks
Frequency Hz 0 Including power
Time interval s 1 —
Distance m 2 —
5.1.1.3 MWF_SEN (0Ch): Sampling resolution
This tag indicates the resolution, minimum bits, the medical waveform is sampled (generally, digitized)
(see Table 4).
Table 4 — Sampling resolution
MWF_SEN* Data Default Encoding range/ Duplicated
length remarks definitions
Unit 1 —
−128 +127
th
10 to 10
Exponent (10 power) 1
12 0Ch See Table 5 Override
Mantissa ≤ 4 e.g. unsigned 16-bit
integer
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 10 — —
s
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
5.1.2.1 General
As described in Figure 2, a frame is composed of data blocks, channels and sequences.
5.1.2.2 MWF_BLK (04h): Data block length
This tag indicates the number of data sampled in a block (see Table 6).
Table 6 — Data block length
MWF_BLK* Data length Default Remarks Duplicated definitions
04 04h ≤ 4 1 — Override
5.1.2.3 MWF_CHN (05h): Number of channels
This tag indicates the number of channels (see 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
5.1.2.4 MWF_SEQ (06h): Number of sequences
This tag indicates the number of sequences (see 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
06 06h ≤ 4 Depends on waveform data length — Override
5.1.3 Waveform
5.1.3.1 General
The waveform type, waveform attributes, and waveform data are encoded as follows.
5.1.3.2 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 0 (Unidentified) —
08 08h Override
2 < 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 (see 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.
5.1.3.3 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.
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
Electrocardiogram
ECG_INTR 5 Intracardiac ECG ECG, intravascular ECG,
cardiac 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
ECG_LATE 8 —
potential
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
EEG_EP 41 Evoked EEG ABR SEP
Electroencephalogram
EEG_CSA 42 Frequency analysis —
(neurophysiological
signal)
EEG_LTRM 43 Long-term EEG Sleeping EEG
EMG 44 Electromyography —
EOG 45 Electrooculography —
Impedance respiratory,
Respiratory RESP 46 Respiratory
airflow, snore and others
Private 49 152 to 65 535 — —
Table 11 — Definition of waveform attributes
MWF_LDN* Data Default Data range, Duplicated
length remarks definitions
Data length = 2,
Waveform code 2 if waveform information
Unidenti-
is encoded
09 09h Override
fied
Waveform
Str ≤ 32 —
information
EXAMPLE Standard 12-lead ECG code, shown in Table 12.
Mainly, standard 12-leads are encoded according to the SCP-ECG (see 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”
129 “Aorta” Coded value indicates as “Arterial pressure” and
information description part indicates “Aorta”
143 “Aorta” Coded value only indicates as “Pressure” and
information description part indicates “Aorta”
EXAMPLE Electroencephalogram waveform.
Generation of waveform codes by combination of electrodes (see Figure 8).
Figure 8 — Generation of waveform code by combination of electrodes
Waveform codes can be generated by combination of electrode codes, as shown in Tables 14 and 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
Table 15 — Example of waveform code generation
Lead − electrode + electrode Waveform code
FP1 - A1 12 74 17994(464A)
FP2 - A2 13 75 18123(46CB)
5.1.3.4 MWF_WAV (1Eh): Waveform data
The entity of waveform data should strictly be aligned as defined in frame attributes (see 4.1.3). If the
waveform data are compressed, the data alignment may depend on the compression method, but the
waveform data after uncompressing 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
5.1.4.1 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 9 for ≤ 127 and to Figure 10 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, i.e. 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).
Figure 9 — Number of channel ≤ 127
Figure 10 — Number of channel ≥ 128
The data length includes all the range of the channel attribute definition (see Figure 11).
Figure 11 — Definition of channel attributes
The indefinite length described in Figure 7 can be used for the channel attribute definition (see
Figures 11 and 12).
Figure 12 — Definition of channel attributes with indefinite length
5.2 Auxiliary rule
5.2.1 Data description
5.2.1.1 MWF_DTP (0Ah): Data type
This tag indicates the type of waveform data (see 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
MWF_DTP Data Default Remarks Duplicated
length definitions
10 0Ah 1 Signed 16-bit integer — Override
Table 19 — Data type code
Value Type of data
0 Signed 16-bit integer, −32 768 to 32 767
1 Unsigned 16-bit integer, 0 to 65 535
2 Signed 32-bit integer
3 Unsigned 8-bit integer
4 16-bit status
5 Signed 8-bit integer
6 Unsigned 32-bit integer
7 32-bit single-precision floating (see IEEE 754)
8 64-bit double-precision floating (see IEEE 754)
9 8-bit 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.
5.2.1.2 MWF_OFF (0Dh): Offset value
This tag indicates an offset value (see Table 20) of sampling data. Encoding of an offset value depends
on the type of encoding data.
Table 20 — Offset value
MWF_OFF Data Default Remarks Duplicated
length definitions
≤ 8 (depends on types of
13 0Dh 0 — Override
encoding data values)
5.2.1.3 MWF_NUL(12h): NULL value
This tag indicates null data. If null values (see 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
MWF_NUL Data Default Remarks Duplicated
length definitions
≤ 8 (depends on types of
18 12h Unused — Override
encoding data values)
5.2.1.4 MWF_CMP (0Eh): Compression
This tag is to compress the encoding waveform.
Table 22 — Compression
MWF_CMP Data Default Remarks Duplicated
length definitions
Compression
code
Data before
14 0Eh Data length 4
compression
Compressed Data length after
Compressed data
data compression
MFER enable encoding of waveforms by compressing (see 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 (see 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
5.2.2.1 MWF_BLE (01h): Endianity
This tag indicates byte alignment in the data section (TLV values only). The big-endian is aligned byte
data from most significant to least significant. The little-endian is aligned from least significant to most
significant (see Tables 26 and 27).
Table 26 — Endianity
MWF_BLE Data Default Remarks Duplicated
length definitions
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).
5.2.2.2 MWF_PNT (07h): Pointer
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 (see
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
MWF_PNT Data length Default Remarks Duplicated definitions
07 07h ≤ 4 Zero or pointer of previous frame — Override
5.2.2.3 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 (see Table 29) need succeed two zero as explained in
Figure 7.
Table 29 — Blank or end-of-contents
MWF_ZRO Data Default Remarks Duplicated
length definitions
00 00h 1 — — Multiple use possible
5.2.3 Information description
5.2.3.1 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). This tag should be described at the top of the tags in the structure
of header and waveform data.
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”.
5.2.3.2 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.
5.2.3.3 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
MWF_EVT Data Default Encoding range/ Duplicated
length remarks definitions
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
5.2.3.4 MWF_INF (15h): Waveform information
This tag indicates waveform information which is generated (refer to Annex C), e.g. catheter information
to measure cardiac output by dye dilution method (see Table 33).
Table 33 — Waveform information
MWF_INF Data Default Data range/remarks Duplicated
length definitions
Information code 2 —
Starting time Point number based on
(point) the sampling interval
21 15h — specified in the root Possible
Duration 4
definition
Waveform
Str < 256 —
information
5.2.3.5 MWF_CND (44h): Acquisition or processing information
This tag represents the acquisition condition or processing information during the waveform
acquisition pro
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