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Convert default resampler from libresample to libsoxr.

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v.audacity
2012-10-09 02:57:19 +00:00
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lib-src/libsoxr/README Normal file
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SoX Resampler Library Copyright (c) 2007-12 robs@users.sourceforge.net
The SoX Resampler library performs one-dimensional sample-rate conversion.
It may be used, for example, to resample PCM-encoded audio. For higher-
dimensional resampling, such as for visual-image processing, you should look
elsewhere.
Its aim is to provide fast, high-quality resampling. At its highest quality
settings, it can produce 32-bit-perfect results with signal occupied-
bandwidths of up to 98%.¹ Resampling ratios can be any (floating point)
value between +/- 8 octaves.
Depending on how the resampler is configured, quality may be traded for
speed, but only to a certain extent: there may be faster, average-quality
resamplers available. Multi-channel resampling can be configured to use
multiple CPU-cores, thus reducing execution time (with a slight expense of
CPU-cycles).
The resampler is currently available either as part of `libsox' (the audio
file-format and effect library), or stand-alone as `libsoxr' (this package).
The APIs of libsox and libsoxr are slightly different, with that of libsoxr
designed specifically for resampling. An application requiring support for
other effects, or for reading-from or writing-to audio files or devices, can
use libsox (or other libraries such as libsndfile or libavformat).
Applications may use either floating-point or integer sample formats, and,
in the case of multiple channels, either channel-interleaved, or split-
channels.
The libsoxr API is currently documented in the header file `soxr.h' and by
example code in the 'examples' directory.
For compatibility with the popular `libsamplerate' library, the header file
`soxr-lsr.h' is provided and may be used as an alternative API. For details
of that API, see http://www.mega-nerd.com/SRC/api.html. Note however, that
libsoxr does not provide a full emulation of libsamplerate; in particular,
`vari-speeding' is not currently supported.
For build and installation instructions, see the file `INSTALL'; for
copyright and licensing information, see the file `copyright'.
The resampler was inspired by Laurent De Soras' paper `The Quest For The
Perfect Resampler', http://ldesoras.free.fr/doc/articles/resampler-en.pdf.
¹ Note that no practical resampler can be bit-perfect to 100% bandwidth.