ANSI CTA-2060:2017 pdf free download – Standard for Consumer EEG File Format (Attuned Container Format)
A key requirement for Attuned was to be able to store essentially any kind of time series data streams with few or no limitations on the number of channels, sampling rates, value formats, and amount or type of associated meta-data. A core use case for the format, is to store data from multiple sensors, which measure diverse physiological data (e.g., EEG and other brain signals, heart rate, motion capture, eye tracking, video, audio, and human interface device inputs), but also any other kind of states that relates to such measurements (e.g., simultaneous application state and events). Attuned was designed with the additional requirements in mind that the file contents shall be streamable (e.g., at the time of recording or playback), the contained streams can be time-synchronized, the file format is efficient in terms of storage space, and that the specification should be simple and compact. Based on these criteria, Attuned was designed as a chunk-based format. In a chunk-based format the entire file is a sequence of chunks, where multiple streams are stored in an interleaved, and therefore streamable fashion. This also enables forward compatibility, where implementations can skip over unknown chunk types (e.g., introduced in a future version of the standard) to allow for space efficient storage of high-volume multi-channel time-series data. Attuned defines a chunk type that can store such data in a simple generic binary array format. These chunks also allow for storage of variable-length binary data, such as video frames, and therefore can hold virtually any kind of streamable data in a storage-efficient manner.
To satisfy the requirement for arbitrary extensible meta-data for each data stream, Attuned provides a flexible text-based chunk type that can hold any kind of structured metadata using XML as the encoding. While it is possible to store arbitrary content in these chunks, to enable a maximum degree of compatibility Attuned recognizes several predefined types of stream content (“content-types”), such as EEG, Video, Audio, MoCap, Markers, etc., and for each content-type, a set of predefined metadata fields, such as channel labels, color space, units, etc., that are found in the appendix of this document. These fields were chosen based on the meta-data present in domain-specific “gold standard” file formats (e.g., traditional video, EEG, or audio file formats). This appendix is expected to be amended in future revisions of the standard to add support for additional content-types or to augment the set of standardized meta- data fields. It shall be emphasized however, that implementers (vendors) are free to add their own custom metadata fields or content-types to satisfy their storage needs. It is encouraged that such extensions to be provided to a public Attuned extension registry. Unless indicated otherwise, registered extensions will automatically be considered for integration into subsequent Attuned revisions. Since fields are easy to add in future extensions, but hard to remove, the initial set of meta-data fields tends to be conservative and covers primarily the essential and widely agreed-upon fields. To address the requirement for time synchronization in a fully general way, each sample has a timestamp, which is stored with an efficient compression scheme to minimize storage overhead. These time stamps may even be read off of different clocks which are allowed to drift relative to each other. For such cases, the format may contain periodic clock offset measurements for each stream held in special type of chunk, which determine how these different clocks relate to each other at any given time and allow for synch