Applications

Some typical uses of the WFDB library are these:

• A waveform editor, such as wave (see the WAVE User’s Guide), reads the digitized signals of a database record and displays them with annotations superimposed on the waveforms. Such a program allows the user to select any portion of the signals for display at various scales, and to add, delete, or correct annotations.
• Signal processing programs (e.g., see section Example 7: A General-Purpose FIR Filter) apply digital filters to the signals of a database record and then record the filtered signals as a new record. Similar programs perform sampling frequency conversion.
• Analysis programs (e.g., see section Example 10: A QRS Detector) read the digitized signals, analyze them, and then record their own annotations.
• An annotation comparator, such as bxb (see section WFDB Application Programs), reads two or more sets of annotations corresponding to a given record, and tabulates discrepancies between them. If the reference annotations supplied with the database are compared in this way with annotations produced using an analysis program, this comparison is a means of establishing the accuracy of the analysis program’s output.

The WFDB library provides the means for programs such as those described above to select a database record, read and write signals, read and write annotations, jump to arbitrary points in the record, and determine attributes of the signals such as the sampling frequency. The library also provides a variety of other more specialized services for programs that need them. The library defines an interface between programs and the database that is sufficiently powerful, general, and efficient to eliminate the need for ad hoc user-written database I/O.