What is this ?
This is a simple audio resampler, written entirely in C and specifically targeting embedded systems. It provides fine control over both the CPU load and memory footprint so it can be easily adapted to a wide range of hardware (e.g., ESP32 to high-end ARM). It is also well suited for ASRC (asynchronous sample rate converter) applications because it allows the resample ratio to be modified continuously and provides a function to query the exact phase position of the resampler (required in the feedback loop of an ASRC). The latest version has optimizations to improve speed and accuracy when performing fixed-ratio conversions, and also supports multithreading for stereo and multichannel files.

0.5 changelog:
The audio resampler initially targeted ASRC applications wherein the resample ratio is infinitely and continuously adjustable. However, this flexibility comes at a cost in performance and accuracy when used in fixed ratio sample rate conversions, which is obviously a very common use case for audio resamplers. This version has an added initialization API for fixed-ratio conversions that provides several optimizations for them, and also adds optional multithreading support to the resample and decimation engines for doing stereo and multichannel conversions in parallel (using either pthreads or native Windows threads). Note that this is all backward compatible with the original API.

There’s also a new tool for benchmarking and testing the resampler and the decimator, including the non-interleaved versions.

• New benchmarking and testing application
• Fix for long-term drift resulting from sample ratios not exactly represented in doubles
• If possible, use a specific reduced number of filers and eliminate the interpolation requirement
• Stereo sample rate conversions are now 2x – 3x faster and more accurate
• Automatic calculation of optimum lowpass filter moved to resampler
• Add optional multithreaded resampling and decimation

Git: https://github.com/dbry/audio-resampler#readme
License: BSD 3-Clause "New" or "Revised"
Windows binaries: https://github.com/dbry/audio-resampler/releases/tag/0.5