Python-SoXR#

GitHub PyPI Read the Docs

High quality, one-dimensional sample-rate conversion library for Python.

Keywords: Resampler, Audio resampling, Samplerate conversion, DSP(Digital Signal Processing)

Python-SoXR is a Python wrapper of libsoxr.

Installation#

pip install soxr

If installation fails, upgrade pip with python -m pip install --upgrade pip and try again.

in Conda environment#

conda install -c conda-forge soxr-python

Note: Conda packge name is soxr-python, not python-soxr.

Basic usage#

import soxr

y = soxr.resample(
    x,          # 1D(mono) or 2D(frames, channels) array input
    48000,      # input samplerate
    16000       # target samplerate
)

If input is not numpy.ndarray, it will be converted to numpy.ndarray(dtype='float32').
dtype should be one of float32, float64, int16, int32.

Output is numpy.ndarray with same dimension and data type of input.

Streaming usage#

Use ResampleStream for real-time processing or very long signal.

import soxr

rs = soxr.ResampleStream(
    44100,              # input samplerate
    16000,              # target samplerate
    1,                  # channel(s)
    dtype='float32'     # data type (default = 'float32')
)

eof = False
while not eof:
    # Get chunk
    ...

    y_chunk = rs.resample_chunk(
        x,              # 1D(mono) or 2D(frames, channels) array input
        last=eof        # Set True at end of input
    )

Output frame count may not be consistent. This is normal operation.
(ex. [0, 0, 0, 186, 186, 166, 186, 186, 168, …])

Requirement#

x86 and ARM processors are supported.

Neon extension is required for ARM CPUs. Without Neon, it may crash or return inaccurate result.

Benchmark#

Sweep, impulse, speed compairsion with other Python resamplers.

https://colab.research.google.com/drive/1XgSOvWlRIau1FYwQG_yRSAhDK3KB8bEL?usp=sharing

Speed comparison summary#

Downsampling 10 sec of 48000 Hz to 44100 Hz.
Ran on Google Colab.

Library

Time on CPU (ms)

soxr (HQ)

7.2

scipy.signal.resample

13.4

soxr (VHQ)

15.8

torchaudio

19.2

lilfilter

21.4

julius

23.1

resampy (kaiser_fast)

62.6

samplerate (sinc_medium)

92.5

resampy (kaiser_best)

256

samplerate (sinc_best)

397

Technical detail#

For technical details behind resampler, see libsoxr docs.

Credit and License#

Python-SoXR is LGPL v2.1+ licensed, following libsoxr’s license.

OSS libraries used#

libsoxr (LGPLv2.1+)#

The SoX Resampler library
https://sourceforge.net/projects/soxr/

Python-SoXR is a Python wrapper of libsoxr.

PFFFT (BSD-like)#

PFFFT: a pretty fast FFT.
https://bitbucket.org/jpommier/pffft/

libsoxr dependency.