.TH zretune 1  "Sept 2012" "version 0.0.1" "USER COMMANDS"
.SH NAME
zretune \- resample an audio file in order to change its pitch
.SH SYNOPSIS
.B zretune
[options] input-file output-file
.SH DESCRIPTION
.B 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.
.SH OPTIONS
.TP
.B --help
Display a short help text.
.TP
.B --ratio pitch ratio
The accepted range is 0.5 to 2.0. The useful range in practice
will be smaller.
.TP
.B --cent pitch change in cents
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.
.SS Output file type
.TP
.B --wav
Produce a WAV file, or for more than 2 channels, a WAVEX file.
This is the default.  
.TP
.B --amb
Produce a WAVEX file with the Ambisonic GUID. Such files should
have the
.B .amb
filename extension.
.TP
.B --caf
Produce a Core Audio file.
.TP
.B --aiff
Produce an AIFF file.
.TP
.B --flac
Produce a FLAC file.
.SS Output sample format
.TP
.B --16bit
Output sample format is signed 16-bit. This option also
enables the use of dithering, described below.
.TP
.B --24bit
Output sample format is 24-bit. This is the default.
.TP
.B --float
Output sample format is 32-bit floating point.
.SS Dithering
.TP
.B --rec
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.
.TP
.B --tri
Add filtered noise with a triangular distribution. Compared to the
rectangular dither this reduces the noise density in the lower
frequency range.
.TP
.B --lips
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.
.SS Timing
.TP
.B --pad
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. 
.SH EXIT STATUS
Zero in case there are no errors, non-zero otherwise.
.SH AUTHOR
Fons Adriaensen (fons (at) linuxaudio.org)