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Name

wav2mit, mit2wav - convert between .wav and WFDB-compatible formats

Synopsis

wav2mit -i file.wav [ options ... ]
mit2wav -o file.wav -r record [ options ... ]

Description

These programs convert files in the widely-used .wav audio file format into WFDB format files (as used in PhysioBank) and vice versa. Most .wav files are already written in a WFDB-compatible format, although the reverse is not true. (An embedded header is required by .wav format, and is allowed but is not usually present in WFDB-format signal files.)

wav2mit creates a WFDB record from file.wav. If the input file is written in an MIT-compatible signal file format, all that is required in this case is to create a suitable WFDB-format .hea header file that describes the .wav file’s format. Some .wav files are written using variants of the format that are not readable by the WFDB library; the current version of wav2mit does not attempt to convert such files, but warns that they are not compatible. Options for wav2mit include:

-h
Print a brief usage summary.
-r record
Create the specified record (default: use the base name of the input file as the record name).

mit2wav reads the specified WFDB-format record (header and signal files) and creates a .wav file containing the same data. Note that much of the data description contained in the WFDB-format header file cannot be preserved in the .wav file. Options for mit2wav include:

-h
Print a brief usage summary.
-n record
Create a header file for the output (.wav) signal file, so that it can be read by WFDB applications as the specified record.

It may be possible to create analog signals by playing the .wav file through a sound card, but you should be aware of the following potential pitfalls:

Your sound card, and the software that comes with it, may not be able to
play .wav files containing three or more signals. If this is a problem, you will need to extract one or two signals to include in the .wav file from your original recording (for example, using xform(1) ).
Your sound card and its software may be unable to play .wav files at
other than certain fixed sampling frequencies (typically 11025, 22050, and 44100 Hz). If this is a problem, you will need to resample the input at one of the frequencies supported by your sound card (for example, using xform(1) ) before converting it to .wav format using this program.
Your sound card may not be able to reproduce the frequencies present in
the input. This is very likely if you are trying to recreate physiologic signals such as ECGs (with most of the useful information in the 0.1 to 30 Hz band) using a consumer sound card (which probably does not reproduce frequencies below the lower limit of human hearing (around 30 Hz). One possible solution to this problem is to create a digital signal containing a higher-frequency carrier signal, amplitude-modulated by the signal of interest, and to convert this AM signal into a .wav file; on playback, an analog AM demodulator would then recover the original low-frequency signal of interest. If you successfully implement this solution, please send details to the author.

Environment

It may be necessary to set and export the shell variable WFDB (see setwfdb(1) ).

Availability

These programs are provided in the convert directory of the WFDB Software Package. Run make in that directory to compile and install them if they have not been installed already.

See Also

a2m(1) , edf2mit, snip(1) , xform(1) , wfdb(3) , header(5)

Author

George B. Moody (george@mit.edu)

Sources

http://www.physionet.org/physiotools/wfdb/convert/wav2mit.c
http://www.physionet.org/physiotools/wfdb/convert/mit2wav.c


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