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zretune(1) USER COMMANDS zretune(1)

NAME

zretune - resample an audio file in order to change its pitch

SYNOPSIS

zretune [options] input-file output-file

DESCRIPTION

zretune resamples an audio file by a the inverse of a ratio given directly or expressed in cents, without changing the nominal sample rate. The result is to change the musical pitch and length of the file. Input can be any audio file readable by the libsndfile library. The output file type is either WAV, WAVEX, CAF, AIFF or FLAC.

OPTIONS

Display a short help text.
The accepted range is 0.5 to 2.0. The useful range in practice will be smaller.
The number of cents by which the pitch is changed. The accepted range is +/- 1200 cents, the useful range in practice will be something like +/- 100 cents.

Output file type

Produce a WAV file, or for more than 2 channels, a WAVEX file. This is the default.
Produce a WAVEX file with the Ambisonic GUID. Such files should have the .amb filename extension.
Produce a Core Audio file.
Produce an AIFF file.
Produce a FLAC file.

Output sample format

--16bit
Output sample format is signed 16-bit. This option also enables the use of dithering, described below.
--24bit
Output sample format is 24-bit. This is the default.
Output sample format is 32-bit floating point.

Dithering

Add white dithering noise with a rectangular distribution. This is the best option if the output data is going to processed again, but in that case it would be advisable to use 24-bit or float.
Add filtered noise with a triangular distribution. Compared to the rectangular dither this reduces the noise density in the lower frequency range.
This uses the optimal error feedback filter described by Stanley Lipschitz. This is recommended is the output is the final distribution format, e.g. for a CD.

Timing

Insert zero valued input samples at the start and end so that the output includes the full symmetric filter response even for the first and last samples.

EXIT STATUS

Zero in case there are no errors, non-zero otherwise.

AUTHOR

Fons Adriaensen (fons (at) linuxaudio.org)

Sept 2012 version 0.0.1