Expand description
An audio sample rate conversion library for Rust.
This library provides resamplers to process audio in chunks.
The ratio between input and output sample rates is completely free. Implementations are available that accept a fixed length input while returning a variable length output, and vice versa.
Rubato can be used in realtime applications without any allocation during processing by preallocating a Resampler and using its input_buffer_allocate and output_buffer_allocate methods before beginning processing. The log feature feature should be disabled for realtime use (it is disabled by default).
Input and output data format
Input and output data is stored non-interleaved.
The output data is stored in a vector of vectors, Vec<Vec<f32>> or Vec<Vec<f64>>.
The inner vectors (Vec<f32> or Vec<f64>) hold the sample values for one channel each.
The input data is similar, except that it allows the inner vectors to be AsRef<[f32]> or AsRef<[f64]>.
Normal vectors can be used since Vec implements the AsRef trait.
Asynchronous resampling
The resampling is based on band-limited interpolation using sinc interpolation filters. The sinc interpolation upsamples by an adjustable factor, and then the new sample points are calculated by interpolating between these points. The resampling ratio can be updated at any time.
Synchronous resampling
Synchronous resampling is implemented via FFT. The data is FFT:ed, the spectrum modified, and then inverse FFT:ed to get the resampled data. This type of resampler is considerably faster but doesn’t support changing the resampling ratio.
SIMD acceleration
Asynchronous resampling
The asynchronous resampler is designed to benefit from auto-vectorization, meaning that the Rust compiler can recognize calculations that can be done in parallel. It will then use SIMD instructions for those. This works quite well, but there is still room for improvement. To address this, it also has optimized SIMD support. This gets enabled at runtime by checking the SIMD support of the CPU.
On x86_64 it will try to use SSE3. The speed benefit compared to auto-vectorization depends on the CPU, but tends to be in the range 20-30% for 64-bit data, and 50-100% for 32-bit data. There is also optional support for AVX on x86_64, and Neon on aarch64 via Cargo features.
Synchronous resampling
The synchronous resamplers benefit from the SIMD support of the RustFFT library.
Cargo features
avx: AVX on x86_64
The avx feature is enabled by default, and enables the use of AVX when it’s available.
The speed increase compared to SSE depends on the CPU, and tends to range from zero to 50%.
On other architectures than x86_64 the avx feature does nothing.
neon: Experimental Neon support on aarch64
Experimental support for Neon is available for aarch64 (64-bit Arm) by enabling the neon feature.
This requires the use of a nightly compiler, as the Neon support in Rust is still experimental.
On a Raspberry Pi 4, this gives a boost of about 10% for 64-bit floats and 50% for 32-bit floats when
compared to the auto-vectorized implementation.
Note that this only works on a full 64-bit operating system.
log: Enable logging
This feature enables logging via the log crate. This is intended for debugging purposes.
Note that outputting logs allocates a std::string::String and most logging implementations involve various other system calls.
These calls may take some (unpredictable) time to return, during which the application is blocked.
This means that logging should be avoided if using this library in a realtime application.
Example
Resample a single chunk of a dummy audio file from 44100 to 48000 Hz. See also the “fixedin64” example that can be used to process a file from disk.
use rubato::{Resampler, SincFixedIn, InterpolationType, InterpolationParameters, WindowFunction};
let params = InterpolationParameters {
sinc_len: 256,
f_cutoff: 0.95,
interpolation: InterpolationType::Linear,
oversampling_factor: 256,
window: WindowFunction::BlackmanHarris2,
};
let mut resampler = SincFixedIn::<f64>::new(
48000 as f64 / 44100 as f64,
2.0,
params,
1024,
2,
).unwrap();
let waves_in = vec![vec![0.0f64; 1024];2];
let waves_out = resampler.process(&waves_in, None).unwrap();Compatibility
The rubato crate requires rustc version 1.40 or newer.
Changelog
- v0.11.0
- New api to allow use in realtime applications.
- Configurable adjust range of asynchronous resamplers.
- v0.10.1
- Fix compiling with neon feature after changes in latest nightly.
- v0.10.0
- Add an object-safe wrapper trait for Resampler.
- v0.9.0
- Accept any AsRef<[T]> as input.
Modules
Structs
A synchronous resampler that needs a fixed number of audio frames for input and returns a variable number of frames.
A synchronous resampler that accepts a fixed number of audio frames for input and returns a fixed number of frames.
A synchronous resampler that needs a varying number of audio frames for input and returns a fixed number of frames.
A struct holding the parameters for interpolation.
Error raised when trying to use a CPU feature which is not supported.
A plain scalar interpolator
An asynchronous resampler that accepts a fixed number of audio frames for input and returns a variable number of frames.
An asynchronous resampler that return a fixed number of audio frames. The number of input frames required is given by the input_frames_next function.
Enums
An identifier for a cpu feature.
Interpolation methods that can be selected. For asynchronous interpolation where the ratio between input and output sample rates can be any number, it’s not possible to pre-calculate all the needed interpolation filters. Instead they have to be computed as needed, which becomes impractical since the sincs are very expensive to generate in terms of cpu time. It’s more efficient to combine the sinc filters with some other interpolation technique. Then sinc filters are used to provide a fixed number of interpolated points between input samples, and then the new value is calculated by interpolation between those points.
The error type used by rubato.
The error type returned when constructing Resampler
Different window functions that can be used to window the sinc function.
Traits
Dummy trait when not supported.
A resampler that us used to resample a chunk of audio to a new sample rate. For asynchronous resamplers, the rate can be adjusted as required.
The trait governing a single sample.
This is a helper trait that can be used when a Resampler must be object safe.
Type Definitions
A result alias for the error type used by rubato.