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Upgrade to libsoxr 0.0.2.

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2012-10-12 23:54:03 +00:00
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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.
The SoX Resampler library `libsoxr' 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).
It aims to be fast (e.g. multi-channel resampling can utilise multiple
CPU-cores), high-quality (i.e. bit-perfect up to 32-bits, for occupied-
bandwidths up to 98%¹), and to allow any rational or irrational resampling
ratio. Phase-response, preserved bandwidth, aliasing, and rejection level
parameters are all configurable; alternatively, simple `preset'
configurations may be selected.
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 interfaces to 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, should use libsox (or other libraries such as libsndfile or
libavformat).
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.
Libsoxr provides a simple API that allows interfacing using any commonly-
used sample format or buffering scheme: clients may use either floating-
point or integer sample formats, and, in the case of multiple channels,
either channel-interleaved, or split channels. The 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
`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.
`vari-speeding' is not supported.
For build and installation instructions, see the file `INSTALL'; for
copyright and licensing information, see the file `copyright'.
copyright and licensing information, see the file `LICENCE'.
The resampler was inspired by Laurent De Soras' paper `The Quest For The
Perfect Resampler', http://ldesoras.free.fr/doc/articles/resampler-en.pdf.
Perfect Resampler', http://ldesoras.free.fr/doc/articles/resampler-en.pdf;
it combines Julius O. Smith's `Bandlimited Interpolation' technique
(https://ccrma.stanford.edu/~jos/resample/resample.pdf) with FFT-based
over-sampling.
Its use of FFTs means that, for real-time resampling, libsoxr may have a
higher latency than non-FFT based resamplers. E.g. when using the `High
Quality' configuration to resample between 44100Hz and 48kHz, the latency is
around 1000 output samples, i.e. roughly 20 ms.
¹ Note that no practical resampler can be bit-perfect to 100% bandwidth.