Crate hertz

useful functions for working with frame-rates, sample-rates, other rates, time durations, frequencies, etc and for keeping a constant framerate.

rate, sample rate, frame rate, fps, frequency, etc express the same concept and are therefore used interchangeably.

you can use hertz to compute the time resolution and frequency range that can be meaningfully analyzed by a short-time fourier transform of a signal:

extern crate hertz;

fn main() {
    let sample_rate = 44100;
    let window_size = 4096;
    let step_size = 512;

    // 11 hertz is the maximum frequency that can be meaningfully analyzed
    assert_eq!(
        11.,
        hertz::rayleigh(sample_rate as f64, window_size as f64).round());

    // 22050 hertz is the maximum frequency that can be meaningfully analyzed
    assert_eq!(
        22050.,
        hertz::nyquist(sample_rate as f64).round());

    // 12 ms is the time resolution we get when analyzing a 44100 hertz
    // signal with a step size of 512
    assert_eq!(
        12.,
        hertz::s_to_ms(hertz::cycles_per_second_to_seconds_per_cycle(
            sample_rate as f64,
            step_size as f64)).round());
}

you can use hertz to keep a constant framerate in a game or other computer graphics application:

fn main() {
    let frames_per_second: usize = 60;

    loop {
        let instant_at_frame_start = std::time::Instant::now();

        // here's where logic and rendering would go.
        // this is never called more than frames_per_second
        // times per second.

        hertz::sleep_for_constant_rate(
            frames_per_second, instant_at_frame_start);
    }
}

Functions

• cycles_per_second_to_seconds_per_cycle
  window duration in seconds sample_rate in hertz
• fps_to_ns_per_frame
  when given frames per second (or sample rate) returns the duration of a single frame
• hertz_range
  frequency range that can be modeled when taking the short time fourier transform of a signal with sample_rate with a sliding window of window_sizew. equivalent to rayleigh(sample_rate, window_size)..nyquist(sample_rate) increase the window size to increase the lower frequency increase the sample rate to increase the upper frequency
• ms_to_ns
  milliseconds to nanoseconds
• ms_to_s
  milliseconds to seconds
• ns_to_ms
  nanoseconds to milliseconds
• ns_to_s
  nanoseconds to seconds
• nyquist
  maximum frequency in hertz that can be meaningfully analyzed with a given sample rate https://en.wikipedia.org/wiki/Short-time_Fourier_transform#Explanation
• rayleigh
  minimum frequency in hertz that can be meaningfully analyzed with a given sample rate and window size https://en.wikipedia.org/wiki/Short-time_Fourier_transform#Rayleigh_frequency
• s_to_ms
  seconds to milliseconds
• s_to_ns
  seconds to nanoseconds
• sleep_for_constant_rate
  useful for keeping a constant framerate