What is the format of the signal files?
Many formats are supported. Most signal files are written in “format 212”, in which two 12-bit samples are bit-packed into three 8-bit bytes. See signal(5) in the WFDB Applications Guide for details on format 212 and on the other supported formats. To determine which format is used for a given signal file, look in the associated header file. (This is a text file that usually has the same name as the signal file, except for a suffix of .hea instead of .dat.) Each line of the header file that begins with the name of the signal file describes the format and contents of a signal within the signal file. See header(5) in the WFDB Applications Guide for details.
Many formats are supported. Most signal files are written in “format 212”, in which two 12-bit samples are bit-packed into three 8-bit bytes, or in “format 16”, in which a 16-bit sample is written as two bytes, least significant byte first (“little-endian”). See signal(5) in the WFDB Applications Guide for details on formats 16 and 212 and on the other supported formats. To determine which format is used for a given signal file, look in the associated header file. (This is a text file that usually has the same name as the signal file, except for a suffix of .hea instead of .dat.) Each line of the header file that begins with the name of the signal file describes the format and contents of a signal within the signal file. See header(5) in the WFDB Applications Guide for details.
, for information about their format and how to read them. • .hea files are short text “header” files used by all of the software that reads the signal files to determine their location and format. In some cases, .hea files also contain structured comments that include information about the subjects (e.g., age, gender, medications, diagnoses). • .atr and .qrs files (and other files described in the database index pages as annotation files) are binary files containing labels (annotations) that point to specific locations within the signal (.dat) files and describe events at those locations. For example, many of these annotations indicate the times of occurrence and types of individual heart beats in records containing ECG signals. See the questions and answers below, beginning with “What is the format of the annotation files?”, for information about the format of these files and how to read them.
