The Signal Metadata Format (SigMF) specifies a way to describe sets of recorded digital signal samples with metadata written in JSON. SigMF can be used to describe general information about a collection of samples, the characteristics of the system that generated the samples, features of signals themselves, and the relationship between different recordings.
This document is available under the CC-BY-SA License.
Copyright of contributions to SigMF are retained by their original authors. All contributions under these terms are welcome.
Table of Contents
- Signal Metadata Format Specification v1.0.0
Sharing sets of recorded signal data is an important part of science and engineering. It enables multiple parties to collaborate, is often a necessary part of reproducing scientific results (a requirement of scientific rigor), and enables sharing data with those who do not have direct access to the equipment required to capture it.
Unfortunately, these datasets have historically not been very portable, and there is not an agreed upon method of sharing metadata descriptions of the recorded data itself. This is the problem that SigMF solves.
By providing a standard way to describe data recordings, SigMF facilitates the sharing of data, prevents the "bitrot" of datasets wherein details of the capture are lost over time, and makes it possible for different tools to operate on the same dataset, thus enabling data portability between tools and workflows.
The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.
JSON keywords are used as defined in ECMA-404.
Augmented Backus-Naur form (ABNF) is used as defined by RFC 5234 and updated by RFC 7405.
Fields defined as "human-readable", a "string", or simply as "text" SHALL be treated as plaintext where whitespace is significant, unless otherwise specified. Fields defined "human/machine-readable" SHOULD be short, simple text strings without whitespace that are easily understood by a human and readily parsed by software.
Specific keywords with semantic meaning in the context of this specification are capitalized after being introduced (e.g., Recording).
The SigMF specification fundamentally describes two types of information:
datasets, and metadata associated with those datasets. Taken together, a Dataset
with its SigMF metadata is a SigMF Recording.
Datasets, for purposes of this specification, are sets of digital measurements
generically called samples in this document. The samples can represent any
time-varying source of information. They MAY, for example, be digital samples
created by digital synthesis or by an Analog-to-Digital Converter. They could
also be geolocation coordinates from a GNSS receiver, temperature readings
from a thermal sensor, or any other stored digital measurement information.
Metadata describes the Dataset with which it is associated. The metadata includes information meant for the human users of the Dataset, such as a title and description, and information meant for computer applications (tools) that operate on the Dataset.
This specification defines a schema for metadata using a core namespace that
is a reserved name and can only be defined by this specification. Other metadata
MAY be described by extension namespaces. This specification also defines a
model and format for how SigMF data should be stored at-rest (on-disk) using JSON.
There are two fundamental filetypes defined by this specification: files with
metadata, and the files that contain the Datasets described by the metadata.
There are two types of files containing metadata, a SigMF Metadata file, and a
SigMF Collection file. There are also two types of Datasets, a SigMF Dataset
file, and a Non-Conforming Dataset file, abbreviated as NCD. NCDs are a
mechanism to support using valid SigMF metadata to describe data that is not
valid SigMF and formatted according to SigMF Dataset requirements.
The primary unit of SigMF is a SigMF Recording, which comprises a Metadata file
and the Dataset file it describes. Collections are an optional feature that are
used to describe the relationships between multiple Recordings.
Collections and multiple Recordings can be packaged for easy storage and
distribution in a SigMF Archive.
┌────────────────────┐
│ │
│ SigMF Collection │
│ ├──┐
│ (optional file) │ │
└──────────┬─────────┘ │
│ │ ┌─────────────────────┐
│ │ stored in │ │
│ links ├────────────► SigMF Archive │
│ │ │ │
│ │ │ (optional file) │
╔══════════▼══════════╗ │ └─────────────────────┘
║ ║ │
║ SigMF Recording ╟─┘
║ ║
║ (base SigMF Object) ║
╚══════════╤══════════╝
│
│ comprises
│
┌─────────────┴──────────────┐
│ │
┌────────▼───────┐ │
│ │ ┌────▼────┐
│ SigMF Metadata ├───────────────► Dataset │
│ │ describes └────┬────┘
│ (file) │ │
└────────────────┘ │
┌─────────┴────────────┐
│ is either │
│ │
┌────────▼────────┐ ┌────────▼─────────┐
│ │ │ │
│ SigMF Dataset │ │ Non-Conforming │
│ │ │ Dataset │
│ (file) │ │ │
└─────────────────┘ │ (file) │
└──────────────────┘
Rules for all files:
- All filetypes MUST be stored in separate files on-disk.
- It is RECOMMENDED that filenames use hyphens to separate words rather than whitespace or underscores.
Rules for SigMF Metadata files:
- A Metadata file MUST only describe one Dataset file.
- A Metadata file MUST be stored in UTF-8 encoding.
- A Metadata file MUST have a
.sigmf-metafilename extension. - A Metadata file MUST be in the same directory as the Dataset file it describes.
- It is RECOMMENDED that the base filenames (not including file extension) of a Recording's Metadata and Dataset files be identical.
Rules for SigMF Dataset files:
- The Dataset file MUST have a
.sigmf-datafilename extension.
Rules for SigMF Non-Conforming Dataset files:
- The NCD file MUST NOT have a
.sigmf-datafilename extension.
Rules for SigMF Collection files:
- The Collection file MUST be stored in UTF-8 encoding.
- The Collection file MUST have a
.sigmf-collectionfilename extension. - The
sigmf-collectionfile MUST be either in the same directory as the Recordings that it references, or in the top-level directory of an Archive (described in later section).
Rules for SigMF Archive files:
- The Archive MUST use the
tararchive format, as specified by POSIX.1-2001. - The Archive file's filename extension MUST be
.sigmf. - The Archive MUST contain at least one SigMF Recording.
- The Archive MAY contain one
.sigmf-collectionfile in the top-level directory. - SigMF Archives MAY contain additional files (not specified by SigMF), and arbitrary directory structures, but the SigMF files within the Archive MUST adhere to all rules above when the archive is extracted.
There are four orthogonal characteristics of sample data: complex or real, floating-point or integer, bit-width, and endianness. The following ABNF rules specify the Dataset formats defined in the Core namespace. Additional Dataset formats MAY be added through extensions.
dataset-format = (real / complex) ((type endianness) / byte)
real = "r"
complex = "c"
type = floating-point / signed-integer / unsigned-integer
floating-point = "f32" / "f64"
signed-integer = "i32" / "i16"
unsigned-integer = "u32" / "u16"
endianness = little-endian / big-endian
little-endian = "_le"
big-endian = "_be"
byte = "i8" / "u8"So, for example, the string "cf32_le" specifies "complex 32-bit floating-point
samples stored in little-endian", the string "ru16_be" specifies "real
unsigned 16-bit samples stored in big-endian", and the string "cu8" specifies
"complex unsigned byte".
Only IEEE-754 single-precision and double-precision floating-point types are supported by the SigMF Core namespace. Note that complex data types are specified by the bit width of the individual I/Q components, and not by the total complex pair bitwidth (like Numpy).
The samples SHOULD be written to the Dataset file without separation, and the Dataset file MUST NOT contain any other characters (e.g., delimiters, whitespace, line-endings, EOF characters).
Complex samples MUST be interleaved, with the in-phase component first (i.e.,
I[0] Q[0] I[1] Q[1] ... I[n] Q[n]). When core:num_channels in the
Global Object (described below) indicates that the Recording contains more than one channel,
samples from those channels MUST be interleaved in the same manner, with
the same index from each channel's sample serially in the Recording. For
example, a Recording with two channels of ri16_le representing real-valued
audio data from a stereo Recording and here labeled L for left and R for
right, the data MUST appear as L[0] R[0] L[1] R[1] ... L[n] R[n].
The data type specified by core:datatype applies to all channels of data
both real and imaginary parts.
SigMF metadata fundamentally takes the form of key/value pairs:
"namespace:name": value,Metadata field names in the top level global Object, captures segment
Objects, or annotations Objects MUST be of this form. All fields other than
those at the top level which contain a : delimiter SHALL only use letters,
numbers, and the _ character; all other characters are forbidden. Field names
MUST NOT start with a number and MUST NOT not be C++20 or Python 3.10 keywords.
When stored on-disk (at-rest), these rules apply:
- The Metadata file MUST be written in JSON, as specified by ECMA-404.
- The entire contents of the Metadata file MUST be contained within a single top-level JSON Object.
- The top-level Object MUST contain three JSON Objects named
global,captures, andannotations. - Metadata key/value pairs SHALL NOT be assumed to have carried over between capture or annotation segments. If a name/value pair applies to a particular segment, then it MUST appear in that segment, even if the value is unchanged relative to the previous segment.
All SigMF metadata is defined using the structural concepts of JSON, and when stored on-disk, metadata MUST be proper JSON to be SigMF compliant.
The values in each key/value pair MUST be one of the following datatypes.
| type | long-form name | description |
|---|---|---|
| int | integer | Signed 64-bit integer. |
| uint | unsigned long | Unsigned 64-bit integer. |
| double | double-precision floating-point number | A 64-bit float as defined by IEEE 754. |
| string | string | A string of characters, as defined by the JSON standard. |
| boolean | boolean | Either true or false, as defined by the JSON standard. |
| null | null | null, as defined by the JSON standard. |
| array | JSON array |
An array of other values, as defined by the JSON standard. |
| object | JSON object |
An object of other values, as defined by the JSON standard. |
| GeoJSON | GeoJSON point Object |
A single GeoJSON point Object as defined by RFC 7946. |
Namespaces provide a way to further classify key/value pairs in metadata.
This specification defines the core namespace. Only this specification
can add fields to the Core namespace.
The goal of the Core namespace is to capture the foundational metadata necessary to work with SigMF data. Some keys within the Core namespace are OPTIONAL, and others are REQUIRED. The REQUIRED fields are those that are minimally necessary to parse and process the Dataset, or that have obvious defaults that are valid. All other fields are OPTIONAL, though they can be strongly RECOMMENDED.
Fields not defined in the Core namespace MAY be defined in extension
namespaces. The SigMF specification defines some extension namespaces to
provide canonical definitions for commonly needed metadata fields that do not
belong in Core. These canonical extension namespaces can be found in the
extensions/ directory of the official SigMF repository. Other extension
namespaces MAY be defined by the user as needed.
- An extension namespace MUST be defined in a single file, named
meta-syntactically as
N.sigmf-ext.md, whereNis the name of the extension. - A
N.sigmf-ext.mdfile MUST be a Github-Flavored Markdown file stored in UTF-8 encoding. - Extensions MUST have version numbers. It is RECOMMENDED that extensions use Semantic Versioning.
- An extension namespace MAY define new top-level SigMF Objects, key/value pairs, new files, new Dataset formats, or new datatypes.
- New key/value pairs defined by an extension namespace MUST be defined in
the context of a specific SigMF top-level Object - i.e.,
global,captures,annotations, or a new user-defined Object. - It is RECOMMENDED that an extension namespace file follow the structure of the canonical extension namespaces.
The global Object consists of key/value pairs that provide information
applicable to the entire Dataset. It contains the information that is minimally
necessary to open and parse the Dataset file, as well as general information
about the Recording itself.
The following names are specified in the Core namespace for use in the Global Object:
| name | required | type | description |
|---|---|---|---|
datatype |
true | string | The SigMF Dataset format of the stored samples in the Dataset file. |
sample_rate |
false | double | The sample rate of the signal in samples per second. |
version |
true | string | The version of the SigMF specification used to create the Metadata file, in the format X.Y.Z. |
num_channels |
false | uint | Total number of interleaved channels in the Dataset file; if omitted this is implied to be 1. For multiple channels of IQ data, it is RECOMMENDED to use SigMF Collections instead of num_channels for widest application support. |
sha512 |
false | string | The SHA512 hash of the Dataset file associated with the SigMF file. |
offset |
false | uint | The index number of the first sample in the Dataset. If not provided, this value defaults to zero. Typically used when a Recording is split over multiple files. All sample indices in SigMF are absolute, and so all other indices referenced in metadata for this recording SHOULD be greater than or equal to this value. |
description |
false | string | A text description of the SigMF Recording. |
author |
false | string | A text identifier for the author potentially including name, handle, email, and/or other ID like Amateur Call Sign. For example "Bruce Wayne bruce@waynetech.com" or "Bruce (K3X)". |
meta_doi |
false | string | The registered DOI (ISO 26324) for a Recording's Metadata file. |
data_doi |
false | string | The registered DOI (ISO 26324) for a Recording's Dataset file. |
recorder |
false | string | The name of the software used to make this SigMF Recording. |
license |
false | string | A URL for the license document under which the Recording is offered. |
hw |
false | string | A text description of the hardware used to make the Recording. |
geolocation |
false | GeoJSON point Object |
The location of the Recording system. |
extensions |
false | array | A list of JSON Objects describing extensions used by this Recording. |
collection |
false | string | The base filename of a collection with which this Recording is associated. |
metadata_only |
false | bool | Indicates the Metadata file is intentionally distributed without the Dataset, used ONLY with Non-Conforming Datasets. |
dataset |
false | string | The full filename of the Dataset file this Metadata file describes, used ONLY with Non-Conforming Datasets. |
trailing_bytes |
false | uint | The number of bytes to ignore at the end of a Dataset, used ONLY with Non-Conforming Datasets. |
The geolocation Field
The location of the Recording system. The location is stored as a single RFC
7946 GeoJSON point Object using
the convention defined by RFC
5870. Per the GeoJSON
specification, the point coordinates use the WGS84 coordinate reference system
and are longitude, latitude (REQUIRED, in decimal degrees), and altitude
(OPTIONAL, in meters above the WGS84 ellipsoid) - in that order. An example
including the altitude field is shown below:
"global": {
...
"core:geolocation": {
"type": "Point",
"coordinates": [-107.6183682, 34.0787916, 2120.0]
}
...
}GeoJSON permits the use of Foreign Members in GeoJSON documents per RFC 7946
Section 6.1. Because the SigMF requirement for the geolocation field is to be
a valid GeoJSON point Object, users MAY include Foreign Member fields here
for user-defined purposes (position valid indication, GNSS SV counts, dillution
of precision, accuracy, etc). It is strongly RECOMMENDED that all fields be
documented in a SigMF Extension document.
Note: Objects named geometry or properties are prohibited Foreign Members
as specified in RFC 7946 Section 7.1.
The extensions Field
A list of JSON Objects describing extensions used by this Recording. Extension Objects MUST contain the three key/value pairs defined below, and MUST NOT contain any other fields.
| name | required | type | description |
|---|---|---|---|
name |
true | string | The name of the SigMF extension namespace. |
version |
true | string | The version of the extension namespace specification used. |
optional |
true | boolean | If this field is false, then the application MUST support this extension in order to parse the Recording; if the application does not support this extension, it SHOULD report an error. |
In the example below, extension-01 is optional, so the application may ignore it if it does not support extension-01. But extension-02 is not optional, so the application must support extension-02 in order to parse the Recording.
"global": {
...
"core:extensions" : [
{
"name": "extension-01",
"version": "0.0.5",
"optional": true
},
{
"name": "extension-02",
"version": "1.2.3",
"optional": false
}
]
...
}The collection Field
The base filename of a collection with which this Recording is associated. If
defined, this field indicates that this Recording is part of a SigMF Collection
(described later in this document). It is strongly RECOMMENDED that if you are
building a Collection, that each Recording referenced by that Collection use
this field to associate up to the relevant sigmf-collection file.
The metadata_only Field
Indicates the Metadata file is intentionally distributed without the Dataset.
When defined, this field should be set to true indicating there is no
corresponding .sigmf-data data file. This may be done when the Dataset will be
generated dynamically from information in the schema, or because just the schema
is sufficient for the intended application. A metadata only distribution is not
a SigMF Recording.
If a Compliant SigMF Recording uses this field, it MAY indicate that the Dataset
was dynamically generated from the metadata. This field SHOULD NOT be used in
conjunction the core:dataset field.
The following fields are associated only with Non-Conforming Datasets and do not need to be considered for Compliant SigMF.
The dataset Field
The full filename of the Dataset file this Metadata file describes, used ONLY with Non-Conforming Datasets. If provided, this string MUST be the complete filename of the Dataset file, including the extension. The Dataset file must be in the local directory, and this string MUST NOT include any aspects of filepath other than the filename.
If a Recording does not have this field, it MUST have a compliant SigMF Dataset (NOT
a Non-Conforming Dataset) which MUST use the same base filename as the Metadata file
and use the .sigmf-data extension. If a SigMF Recording or Archive is renamed this
field MUST also be updated, because of this it is RECOMMENDED that Compliant SigMF
Recordings avoid use of this field.
This field SHOULD NOT be used in conjunction the core:metadata_only field. If both
fields exist and the file specified by core:dataset exists, then core:metadata_only
SHOULD be ignored by the application.
The trailing_bytes Field
The number of bytes to ignore at the end of a Dataset, used ONLY with Non-Conforming Datasets. This field indicate that some number of bytes at the end of the data file do not contain sample data should be ignored for processing. This can be used to ignore footer data in non-SigMF filetypes (e.g.: BLUE file extended header).
The captures field is an array of capture segment Objects that describe the
parameters of the signal capture. It MUST be sorted by the value of each
capture segment's core:sample_start key, ascending.
All samples in a dataset are contained in exactly one capture segment. There
SHOULD be at least one segment defined in the captures ; if there are no items in the captures
array it is implied that a single capture with the core:sample_start field
equal to zero. No other metadata is implied.
Capture Segment Objects are composed of key/value pairs, and each Segment describes
a chunk of samples that can be mapped into memory for processing. Each Segment
MUST contain a core:sample_start key/value pair, which indicates the sample index
relative to the Dataset where this Segment's metadata applies. The fields that are
described within a Capture Segment are scoped to that Segment only and need to be
explicitly declared again if they are valid in subsequent Segments.
The following names are specified in the Core namespace for use in Capture Segment Objects:
| name | required | type | description |
|---|---|---|---|
sample_start |
true | uint | The sample index in the Dataset file at which this Segment takes effect. |
global_index |
false | uint | The index of the sample referenced by sample_start relative to an original sample stream. |
frequency |
false | double | The center frequency of the signal specified in Hz. |
datetime |
false | string | An ISO-8601 string indicating the timestamp of the sample index specified by sample_start. |
header_bytes |
false | uint | The number of bytes preceding a chunk of samples that are not sample data, used ONLY with Non-Conforming Datasets. |
The sample_start Field
The sample index in the Dataset file at which this Segment takes effect. This field is specified relative to the first sample in the recorded Dataset file. If the Dataset is a SigMF Dataset file, this field can be immediately mapped to physical disk location since conforming Datasets only contain sample data.
The global_index Field
The index of the sample referenced by sample_start, relative to an original
sample stream. This field describes an index relative to an original sample
stream, the entirety of which may not have been captured in a recorded Dataset.
If omitted, this value SHOULD be treated as equal to sample_start.
For example, some hardware devices are capable of 'counting' samples at the point of data conversion. This sample count is commonly used to indicate a discontinuity in the datastream between the hardware device and processing.
For example, in the below Captures array, there are two Segments describing
samples in a SigMF Dataset file. The first Segment begins at the start of the
Dataset file. The second segment begins at sample index 500 relative to the
recorded samples (and since this is a conforming SigMF Dataset, is physically
located on-disk at location sample_start * sizeof(sample)), but the
global_index reports this was actually sample number 1000 in the original
datastream, indicating that 500 samples were lost before they could be recorded.
...
"captures": [
{
"core:sample_start": 0,
"core:global_index": 0
},
{
"core:sample_start": 500,
"core:global_index": 1000
}
],
...The datetime Field
An ISO-8601 string indicating the timestamp of the sample index specified by
sample_start. The format is defined by RFC
3339, where the only allowed
time-offset is Z, indicating the UTC/Zulu timezone. The ABNF description is:
date-fullyear = 4DIGIT
date-month = 2DIGIT ; 01-12
date-mday = 2DIGIT ; 01-28, 01-29, 01-30, 01-31 based on month/year
time-hour = 2DIGIT ; 00-23
time-minute = 2DIGIT ; 00-59
time-second = 2DIGIT ; 00-58, 00-59, 00-60 based on leap second rules
time-secfrac = "." 1*DIGIT
time-offset = "Z"
partial-time = time-hour ":" time-minute ":" time-second [time-secfrac]
full-date = date-fullyear "-" date-month "-" date-mday
full-time = partial-time time-offset
date-time = full-date "T" full-timeThus, timestamps take the form of YYYY-MM-DDTHH:MM:SS.SSSZ, where any number
of digits for fractional seconds is permitted.
The following fields are associated only with Non-Conforming Datasets and do not need to be considered for Compliant SigMF.
The header_bytes Field
The number of bytes preceding a chunk of samples that are not sample data, used ONLY with Non-Conforming Datasets. The specified bytes are located in the dataset at the start of where the chunk of samples referenced by this Captures Segment would otherwise begin, and are not part of the time series sample data. This field is intended to identify either global (e.g.: header metadata from a MIDAS BLUE file, which would be included in the first Capture's metadata), or segment specific header data (e.g.: repeating frame information from a VRT raw data capture). If omitted, this value is considered to be zero. If this field is non-zero, the Dataset is by definition a Non-Conforming Dataset.
For example, the below Metadata for a Non-Conforming Dataset contains
two segments describing chunks of 8-bit complex samples (2 bytes per sample)
recorded to disk with 4-byte headers that are not valid for
processing. Thus, to map these two chunks of samples into memory, a reader
application would map the 500 samples (equal to 1000 bytes) in the first
Segment, starting at a file offset of 4 bytes, and then the remainder of the
file through EOF starting at a file offset of 1008 bytes (equal to the size
of the previous Segment of samples plus two headers).
{
"global": {
"core:datatype": "cu8",
"core:version": "1.0.0",
"core:dataset": "non-conforming-dataset-01.dat"
},
"captures": [
{
"core:sample_start": 0,
"core:header_bytes": 4,
},
{
"core:sample_start": 500,
"core:header_bytes": 4,
}
],
"annotations": []
}The annotations value is an array of annotation Objects that describe
anything regarding the signal data not part of the Captures and Global
Objects. It MUST be sorted by the value of each Annotation Segment's
core:sample_start key, ascending.
Annotation segment Objects contain key/value pairs and MUST contain a
core:sample_start key/value pair, which indicates the first index
at which the rest of the Segment's key/value pairs apply.
The following names are specified in the Core namespace for use in Annotation Segment Objects:
| name | required | type | description |
|---|---|---|---|
sample_start |
true | uint | The sample index at which this Segment takes effect. |
sample_count |
false | uint | The number of samples that this Segment applies to. |
freq_lower_edge |
false | double | The frequency (Hz) of the lower edge of the feature described by this annotation. |
freq_upper_edge |
false | double | The frequency (Hz) of the upper edge of the feature described by this annotation. |
label |
false | string | A short form human/machine-readable label for the annotation. |
generator |
false | string | Human-readable name of the entity that created this annotation. |
comment |
false | string | A human-readable comment. |
uuid |
false | string | A RFC-4122 compliant UUID string of the form xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx. |
latitude |
false | The latitude corresponding to the annotation (DEPRECATED, use core:geolocation). |
|
longitude |
false | The longitude corresponding to the annotation (DEPRECATED, use core:geolocation). |
The sample_start Field
The sample index at which this Segment takes effect. There is no limit to the
number of annotations that can apply to the same group of samples. If two
annotations have the same sample_start, there is no defined ordering between
them.
The sample_count Field
The number of samples that this Segment applies to. If sample_count is not
provided, it SHOULD be assumed that the annotation applies from sample_start
through the end of the Dataset, in all other cases sample_count MUST be
provided.
The freq_lower_edge Field
The frequency (Hz) of the lower edge of the feature described by this
annotation. This value SHOULD be at RF if the feature is at a known RF
frequency. If there is no known center frequency (as defined by the
core:frequency field in the relevant Capture Segment Object), this field is
relative to baseband (0 Hz). If specified, the freq_upper_edge field MUST also
be defined.
The freq_upper_edge Field
The frequency (Hz) of the upper edge of the feature described by this
annotation. This value SHOULD be at RF if the feature is at a known RF
frequency. If there is no known center frequency (as defined by the
core:frequency field in the relevant Capture Segment Object), this field is
relative to baseband (0 Hz). If specified, the freq_lower_edge field MUST also
be defined.
The label Field
A short form human/machine-readable label for the annotation. The label field
MAY be used for any purpose, but it is RECOMMENDED that it be limited to no more
than 20 characters as a common use is a short form GUI indicator. Similarly, it
is RECOMMENDED that any user interface making use of this field be capable of
displaying up to 20 characters.
The sigmf-collection file contains metadata in a single top-level Object
called a collection. The Collection Object contains key/value pairs that
describe relationships between SigMF Recordings.
The Collection Object associates SigMF Recordings together by specifying
SigMF Recording Objects in the core:streams JSON array. Each Object
describes a specific associated SigMF Recording.
The following rules apply to SigMF Collections:
- The Collection Object MUST be the only top-level Object in the file.
- Keys in the Collection Object SHOULD use SigMF Recording Objects when referencing SigMF Recordings.
- SigMF Recording Objects MUST contain both a
namefield, which is the base-name of a SigMF Recording, and ahashwhich is the SHA512 hash of the Recording Metadata file[base-name].sigmf-meta. - SigMF Recording Objects MUST appear in a JSON array.
The following names are specified in the core namespace for use in the collection
Object.
| name | required | type | description |
|---|---|---|---|
version |
true | string | The version of the SigMF specification used to create the Collection file. |
description |
false | string | A text description of the SigMF Collection. |
author |
false | string | A text identifier for the author potentially including name, handle, email, and/or other ID like Amateur Call Sign. For example "Bruce Wayne bruce@waynetech.com" or "Bruce (K3X)". |
collection_doi |
false | string | The registered DOI (ISO 26324) for a Collection. |
license |
false | string | A URL for the license document under which this Collection metadata is offered. |
extensions |
false | array | A list of Objects describing extensions used by this Collection. |
streams |
false | array | An ordered array of SigMF Recording Tuples, indicating multiple recorded streams of data (e.g., channels from a phased array). |
Example top-level.sigmf-collection file:
{
"collection": {
"core:version": "1.0.0",
"core:extensions" : [
{
"name": "antenna",
"version": "1.0.0",
"optional": true
}
],
"antenna:hagl": 120,
"antenna:azimuth_angle": 98,
"core:streams": [
{
"name": "example-channel-0-basename",
"hash": "b4071db26f5c7b0c70f5066eb9bc3a8b506df0f5af09991ba481f63f97f7f48e9396584bc1c296650cd3d47bc4ad2c5b72d2561078fb6eb16151d2898c9f84c4"
},
{
"name": "example-channel-1-basename",
"hash": "7132aa240e4d8505471cded716073141ae190f763bfca3c27edd8484348d6693d0e8d3427d0bf1990e687a6a40242d514e5d1995642bc39384e9a37a211655d7"
}
]
}
}SigMF Recording Objects reference the base-name of the SigMF Recording and the
SHA512 hash of the Metadata file, and SHOULD BE specified as a JSON Object:
{
"name": "example-channel-0-basename",
"hash": "b4071db26f5c7b0c70f5066eb9bc3a8b506df0f5af09991ba481f63f97f7f48e9396584bc1c296650cd3d47bc4ad2c5b72d2561078fb6eb16151d2898c9f84c4"
}Recording Tuples are also permitted and have a similar form. The order of
the tuple: [name, hash] is REQUIRED when using tuples:
["example-channel-0-basename", "b4071db26f5c7b0c70f5066eb9bc3a8b506df0f5af09991ba481f63f97f7f48e9396584bc1c296650cd3d47bc4ad2c5b72d2561078fb6eb16151d2898c9f84c4"]Tuples will be removed in SigMF version 2.0, so JSON Objects are RECOMMENDED.
Additional optional user fields MAY be added to SigMF Recording Objects if
they are defined in a compliant SigMF extension. Additional fields are NOT
permitted in tuples.
Open licenses are RECOMMENDED but you can specify any license. You can refer to resources provided by the Open Data Commons when deciding which open license fits your needs best. Cornell University has also created a guide to help you make these choices.
The term 'SigMF Compliant' is used throughout this document, which can take on one of several contextually dependent meanings. In order for a schema, Recording, or application to be 'SigMF Compliant', specific conditions MUST be met, outlined in the following sections. Provided the below criteria are met, an application or Recording can indicate that it is 'SigMF Compliant'.
In order to be 'SigMF Compliant', a schema MUST meet the following requirements:
- Adheres to and supports the metadata file naming conventions,
objects,namespaces, andnamesspecified by this document. - MUST contain all REQUIRED fields with the correct datatype listed the
corenamespace, and any namespace listed in theextensionsarray. - MUST NOT contain fields that are not outlined in the
coreor a listedextensionsnamespace.
In order to be 'SigMF Compliant', a Recording MUST meet the following requirements:
- The Recording's schema file MUST be SigMF Compliant.
- Adheres to and supports the file naming conventions and Dataset formats specified in this document.
- Stores data using the on-disk representation described by the
datatype.
Recordings with Non-Conforming Datasets MAY have SigMF Compliant schema, but cannot be SigMF Compliant Recordings.
In order to be 'SigMF Compliant', a Collection must meet the following requirements:
- The collection MUST contain only compliant Recordings.
- The Collection Object MUST only contain SigMF key/value pairs provided by the core specification or a compliant SigMF extension.
In order to be 'SigMF Compliant', an application MUST meet the following requirements:
- Is capable of parsing and loading SigMF Compliant Recordings. Support for SigMF Collections and Archives is RECOMMENDED but not REQUIRED.
- Adheres to and supports the file rules, Dataset formats,
objects,namespaces, andnamesspecified by this document. - MUST be able to ignore any
objectornamespacenot specified by this document and still function normally. - Capture Segments referring to non-existent samples SHOULD be ignored.
- MUST treat consecutive Capture Segments whose metadata is equivalent for purposes of that application (i.e., it may be different in values ignored by the application such as optional values or unknown extensions) as it would a single segment.
- MUST support parsing ALL required fields in the
corenamespace, and defines which optional fields are used by the application. - MUST define which extensions are supported, parses ALL required fields in listed extension namespaces, and defines which optional fields are used. This definition can be in user documentation or within the code itself, though explicit documentation is RECOMMENDED.
- Support for ALL SigMF Datatypes is NOT REQUIRED as certain datatypes may not make sense for a particular application, but Compliant applications MUST define which datatypes are supported, and be capable of loading Compliant Recordings using supported datatypes.
Compliant applications are NOT REQUIRED to support Non-Conforming Datasets or
Metadata Only schema files, but it is RECOMMENDED that they parse the respective
metadata fields in the global Object to provide descriptive messages to users
regarding why the files are not supported.
Support for SigMF Collections is OPTIONAL for SigMF Compliant applications, however it is RECOMMENDED that applications implementing SigMF make use of Collections when appropriate for interoperability and consistency.
To cite the SigMF specification, we recommend the following format:
The Signal Metadata Format (SigMF), <release>, <date of release>, https://sigmf.orgThis specification originated at the DARPA Brussels Hackfest 2017.