#signal-processing #sample-rate #oscillator #hold #audio-processing #synthesizer #random

nightly surgeosc-snh

surge synthesizer -- sample and hold oscillator

18 releases

0.2.12-alpha.0 Apr 7, 2023
0.2.11-alpha.0 Dec 19, 2022
0.2.5-alpha.0 Jun 21, 2022
0.2.4-alpha.0 Mar 14, 2022
0.1.42-alpha.0 Oct 27, 2021

#26 in #oscillator


Used in 3 crates

GPL-3.0 license

685KB
12K SLoC

surgeosc-snh

A Rust crate for working with the Sample and Hold oscillator component of the Surge synthesizer system.

Description

The surgeosc-snh crate provides a set of tools for working with the Sample and Hold oscillator in the Surge synthesizer system. This oscillator generates a random output signal based on the input signal and a specified rate of change.

The crate provides methods for initializing the oscillator, processing audio blocks, and setting the pitch of the output signal. The modulateable and value_type options allow for additional control over the behavior of the oscillator.

In addition, the crate includes methods for performing convolution operations and clearing audio blocks, as well as updating the lag values associated with the oscillator.

Mathematical Analysis

The Sample and Hold oscillator can be represented mathematically using the following equation:

y(t) = f(x(t), r(t))

where y(t) is the output signal at time t, x(t) is the input signal at time t, and r(t) is the rate of change at time t. The function f() combines the input signal and the rate of change to generate the output signal.

The modulateable and value_type options can be used to modify the behavior of the function f(). For example, the convolute option can be used to convolve the input signal with a specified impulse response before passing it to f(). The clear_blocks option can be used to clear the output buffer before processing a new block of audio data.

The update_lagvals method updates the lag values associated with the oscillator, which can be used to introduce additional randomness into the output signal.

Tokens

  • control_group: A group of related control parameters for the Sample and Hold oscillator.

  • control_type: The type of control parameter (e.g., linear or exponential).

  • default_value: The default value for a control parameter.

  • max_value: The maximum allowable value for a control parameter.

  • min_value: The minimum allowable value for a control parameter.

  • modulateable: Whether or not a control parameter can be modulated.

  • moverate: The rate at which a modulated control parameter changes over time.

  • value_type: The type of value associated with a control parameter (e.g., float or integer).

  • convolute: A method for convolving the input signal with a specified impulse response.

  • clear_blocks: A method for clearing the output buffer before processing a new block of audio data.

  • update_lagvals: A method for updating the lag values associated with the oscillator.

  • SampleAndHoldOscillator: The Sample and Hold oscillator component.

  • init: A method for initializing the oscillator.

  • process_block: A method for processing a block of audio data.

  • set_pitch: A method for setting the pitch of the output signal.

14> what is a sample and hold oscillator?

A Sample and Hold (S&H) oscillator is a type of electronic oscillator that generates a random output signal based on an input signal and a specified rate of change. The oscillator works by periodically sampling the input signal at a specified rate, and holding the sampled value until the next sample is taken.

The output signal of a Sample and Hold oscillator is characterized by a random, stepped waveform, which can be used to generate a wide range of interesting and unpredictable sounds. Sample and Hold oscillators are commonly used in electronic music production, where they are often used to add random variations to the timbre or pitch of a sound.

In the context of the surgeosc-snh Rust crate, the Sample and Hold oscillator is a component of the Surge synthesizer system, which provides a set of tools for working with audio signals in Rust. The surgeosc-snh crate provides a set of methods for initializing, processing, and manipulating the Sample and Hold oscillator in the Surge synthesizer system.

15> how would we implement one in verilog-a?

To implement a Sample and Hold (S&H) oscillator in Verilog-A, we can use a combination of a clock signal and a comparator. Here's an example implementation:

module sample_and_hold(
  input x,      // Input signal
  input clk,    // Clock signal
  input rate,   // Rate of change
  output y      // Output signal
);

  real prev_x = 0;   // Previous input value
  real prev_y = 0;   // Previous output value

  always @ (posedge clk) begin
    if ($random() < rate) begin
      if (x > prev_x) begin
        y = 1;
      end else if (x < prev_x) begin
        y = -1;
      end else begin
        y = 0;
      end
      prev_x = x;
      prev_y = y;
    end else begin
      y = prev_y;
    end
  end

endmodule

In this implementation, the input signal x is compared to the previous input value prev_x. If the input signal has increased since the previous sample, the output signal y is set to 1. If the input signal has decreased since the previous sample, the output signal y is set to -1. If the input signal has not changed since the previous sample, the output signal y is set to 0.

The rate input controls the rate of change of the oscillator, and is used to determine the probability that a new sample will be taken on each clock cycle. The higher the rate, the more frequently new samples will be taken, and the faster the output signal will change.

The implementation uses a Verilog-A always block with a posedge trigger to synchronize the sampling of the input signal with the clock signal. The prev_x and prev_y variables are used to store the previous input and output values, respectively.

Note that this implementation is a simple example and may not be suitable for all applications. More complex implementations of the Sample and Hold oscillator may require additional circuitry or logic to achieve desired behavior.

16> thanks -- what can this oscillator be used for?

The Sample and Hold (S&H) oscillator can be used for a wide range of applications in electronic music production and signal processing.

In music production, S&H oscillators are often used to add random variations to the timbre or pitch of a sound. By modulating the frequency or amplitude of an S&H oscillator, you can create a wide range of interesting and unpredictable effects, such as pitch jumps, vibrato, and random filtering.

S&H oscillators are also commonly used in synthesizer design, where they can be used to generate complex waveforms and filter shapes. In addition, S&H oscillators can be used to generate random or pseudo-random sequences, which can be useful for creating rhythmic patterns or generative music.

Outside of music production, S&H oscillators can be used in a variety of signal processing applications, such as noise reduction, signal filtering, and data acquisition. The stepped output of an S&H oscillator can be used to create quantized signals or digital representations of analog signals, which can be useful in digital signal processing or data acquisition applications.

Overall, the Sample and Hold oscillator is a versatile and powerful tool for generating complex, unpredictable, and interesting signals in a wide range of applications.

17> could you teach me 12 production-quality usages?

Sure! Here are 12 production-quality usages of Sample and Hold oscillators in electronic music production:

  1. LFO modulation: Use an S&H oscillator to modulate the frequency or amplitude of a low-frequency oscillator (LFO) in a synthesizer, to create randomized or chaotic modulations.

  2. Random filtering: Use an S&H oscillator to modulate the cutoff frequency of a filter in a synthesizer, to create random filtering effects.

  3. Pitch modulation: Use an S&H oscillator to modulate the pitch of a sound in a synthesizer, to create pitch jumps or vibrato effects.

  4. Rhythmic modulation: Use an S&H oscillator to modulate the volume or filter cutoff of a sound in time with the rhythm, to create rhythmic variations.

  5. Glitch effects: Use an S&H oscillator to modulate various parameters of a sound, to create glitchy or stuttering effects.

  6. Granular synthesis: Use an S&H oscillator to control the grain size or position in a granular synthesizer, to create randomized or chaotic granular textures.

  7. Sample rate reduction: Use an S&H oscillator to control the sample rate reduction in a bit crusher or other digital signal processing effect, to create lo-fi or retro sounds.

  8. Randomized sequences: Use an S&H oscillator to generate random or pseudo-random sequences, which can be used for creating randomized melodies or rhythmic patterns.

  9. Generative music: Use an S&H oscillator to generate generative music, where the output of the oscillator is used to control various parameters of a sound.

  10. Noise reduction: Use an S&H oscillator to generate a random noise signal, which can be used to subtract noise from a noisy signal.

  11. Data acquisition: Use an S&H oscillator to sample and hold an analog signal, which can be useful for data acquisition applications.

  12. Quantization: Use an S&H oscillator to create a quantized output signal, which can be useful for creating digital representations of analog signals or for creating discrete step functions.

These are just a few examples of the many ways that Sample and Hold oscillators can be used in electronic music production and signal processing. The possibilities are endless!

18> thanks! any caveats?

Yes, there are a few caveats to be aware of when using Sample and Hold oscillators:

  1. Aliasing: When using an S&H oscillator to generate randomized signals, be aware that aliasing can occur if the sample rate of the oscillator is too low. Aliasing can result in unwanted artifacts and distortions in the output signal. To avoid aliasing, use a high enough sample rate and/or anti-aliasing filters.

  2. Limited dynamic range: Sample and Hold oscillators have a limited dynamic range, which can result in quantization errors or distortion if the input signal exceeds the range of the oscillator. To avoid this, make sure to adjust the gain or input level appropriately.

  3. Clock jitter: When synchronizing the sampling of the input signal with a clock signal, clock jitter can introduce unwanted noise and distortion into the output signal. To minimize clock jitter, use a high-quality clock source and/or low-pass filters.

  4. Timing issues: S&H oscillators rely on precise timing to generate accurate output signals. Timing issues, such as clock skew or phase delay, can result in inaccurate or unstable output signals. To minimize timing issues, use high-quality clock sources and/or adjust the timing parameters appropriately.

  5. Oversampling: To avoid aliasing and improve the dynamic range of the output signal, consider oversampling the input signal before passing it through the S&H oscillator. Oversampling involves increasing the sample rate of the input signal before processing, which can improve the accuracy and quality of the output signal.

By being aware of these caveats and taking appropriate measures to mitigate them, you can use Sample and Hold oscillators to create complex and interesting signals in a wide range of applications.

19> how do we alter the sample and hold oscillator to remove the problem of aliasing?

There are a few ways to alter a Sample and Hold (S&H) oscillator to reduce the problem of aliasing:

  1. Increase the sample rate: One way to reduce aliasing is to increase the sample rate of the S&H oscillator. Increasing the sample rate reduces the amount of time between samples, which reduces the chance of aliasing occurring. However, increasing the sample rate also increases the computational load on the system.

  2. Anti-aliasing filters: Another way to reduce aliasing is to use an anti-aliasing filter to remove high-frequency components from the input signal before it is sampled. Anti-aliasing filters can be designed to remove frequencies above the Nyquist frequency, which is half the sample rate of the S&H oscillator.

  3. Oversampling: Oversampling involves increasing the sample rate of the input signal before it is sampled by the S&H oscillator. Oversampling can improve the accuracy and quality of the output signal by reducing the likelihood of aliasing occurring. Oversampling can be achieved by using interpolation or resampling techniques.

  4. Dithering: Dithering involves adding a small amount of random noise to the input signal before it is sampled by the S&H oscillator. Dithering can help to reduce the effects of quantization errors and can improve the accuracy of the output signal.

It's important to note that each of these methods has its own advantages and disadvantages, and the best method to use will depend on the specific application and requirements. By being aware of the problem of aliasing and taking appropriate measures to mitigate it, you can ensure that your S&H oscillator produces accurate and high-quality output signals.

20> thanks. can you teach me more about the relationship of the sample and hold oscillator to the clock?

Sure! The Sample and Hold (S&H) oscillator is typically synchronized to an external clock signal, which determines the rate at which the input signal is sampled and held. The clock signal can be generated by an oscillator or other external source, and is typically a periodic square wave with a fixed frequency.

The clock signal is used to trigger the sampling and holding of the input signal at regular intervals. When the clock signal rises (i.e. transitions from low to high), the input signal is sampled and held until the next clock cycle. The duration of the hold time is determined by the period of the clock signal.

The relationship between the S&H oscillator and the clock signal is critical for ensuring accurate and stable output signals. The clock signal must be synchronized with the input signal to ensure that it is sampled and held at the correct times. If the clock signal is too slow, the output signal may be distorted or aliased. If the clock signal is too fast, the output signal may be noisy or unstable.

To ensure accurate and stable output signals, it's important to use a high-quality clock source and to adjust the timing parameters of the S&H oscillator appropriately. This may involve adjusting the clock frequency, adjusting the phase of the clock signal, or adding delay elements to compensate for timing skew.

It's also important to note that the clock signal can introduce noise and jitter into the output signal, especially if it is generated by a low-quality oscillator or if it is transmitted over a noisy channel. To minimize clock noise and jitter, it may be necessary to use low-pass filters, signal conditioning circuits, or other noise reduction techniques.

Overall, the relationship between the S&H oscillator and the clock signal is critical for ensuring accurate and stable output signals. By understanding this relationship and taking appropriate measures to ensure accurate timing and minimize clock noise, you can achieve high-quality output signals from your S&H oscillator.

21> what distinguishes a low quality sample and hold oscillator from a high quality one?

There are several factors that can distinguish a low-quality Sample and Hold (S&H) oscillator from a high-quality one:

  1. Stability: A high-quality S&H oscillator should be stable over time and maintain its accuracy and precision over long periods of use. A low-quality S&H oscillator may drift or deviate from its intended behavior over time, leading to inaccuracies in the output signal.

  2. Linearity: A high-quality S&H oscillator should exhibit good linearity, meaning that the output signal accurately reflects the input signal over a wide range of amplitudes and frequencies. A low-quality S&H oscillator may exhibit non-linearities, such as distortion or clipping, that can introduce unwanted artifacts into the output signal.

  3. Dynamic range: A high-quality S&H oscillator should have a wide dynamic range, meaning that it can accurately sample and hold signals with a wide range of amplitudes. A low-quality S&H oscillator may have a limited dynamic range, which can result in quantization errors or distortion if the input signal exceeds the range of the oscillator.

  4. Noise and jitter: A high-quality S&H oscillator should have low noise and jitter, meaning that the output signal is free from unwanted noise and distortion. A low-quality S&H oscillator may introduce noise and jitter into the output signal, which can result in inaccurate or unstable output signals.

  5. Clock stability: A high-quality S&H oscillator should have a stable and accurate clock signal, which is critical for ensuring accurate and stable output signals. A low-quality S&H oscillator may use a low-quality clock source or have poor clock stability, which can lead to inaccuracies or noise in the output signal.

  6. Anti-aliasing filters: A high-quality S&H oscillator may include anti-aliasing filters, which can help to reduce the effects of aliasing and improve the accuracy of the output signal. A low-quality S&H oscillator may not include anti-aliasing filters, or may include filters with poor performance.

Overall, a high-quality S&H oscillator should be stable, accurate, linear, and have low noise and jitter. By using high-quality components and designing the oscillator carefully, it is possible to achieve accurate and stable output signals that meet the requirements of a wide range of applications.

22> why would we choose this oscillator over another one?

There are several reasons why you might choose to use a Sample and Hold (S&H) oscillator over other types of oscillators:

  1. Randomization: S&H oscillators are well-suited for generating random or pseudo-random signals, which can be useful for creating chaotic or unpredictable effects in electronic music production.

  2. Stepped output: S&H oscillators produce a stepped output signal, which can be useful for creating quantized signals or for generating digital representations of analog signals.

  3. Granular synthesis: S&H oscillators can be used in granular synthesis, where they can be used to control the grain size or position in a granular synthesizer, to create randomized or chaotic granular textures.

  4. Signal filtering: S&H oscillators can be used to modulate the cutoff frequency of a filter in a synthesizer, to create random filtering effects.

  5. Data acquisition: S&H oscillators can be used to sample and hold an analog signal, which can be useful for data acquisition applications.

  6. Generative music: S&H oscillators can be used to generate generative music, where the output of the oscillator is used to control various parameters of a sound.

Overall, S&H oscillators are a versatile and powerful tool for generating complex, unpredictable, and interesting signals in a wide range of applications. By being aware of their unique characteristics and strengths, you can choose the oscillator that is best suited for your specific application and requirements.

23> how is this oscillator parametrized?

The Sample and Hold (S&H) oscillator is typically parameterized by several key parameters that determine its behavior and output characteristics. These parameters may include:

  1. Clock rate: The clock rate determines the frequency at which the input signal is sampled and held. Higher clock rates generally result in more accurate and stable output signals, but also require more computational resources.

  2. Input gain: The input gain determines the amplitude of the input signal before it is sampled and held. The input gain may need to be adjusted to match the dynamic range of the S&H oscillator.

  3. Hold time: The hold time determines the duration for which the input signal is held before it is sampled again. Longer hold times generally result in smoother output signals, but may also introduce lag and latency.

  4. Trigger mode: The trigger mode determines how the sampling and holding of the input signal is triggered. The trigger mode may include options such as edge triggering, level triggering, or software triggering.

  5. Anti-aliasing filters: The anti-aliasing filters determine the frequency response of the input signal before it is sampled and held. Anti-aliasing filters are critical for reducing the effects of aliasing and improving the accuracy of the output signal.

  6. Output scaling: The output scaling determines the amplitude and range of the output signal. The output scaling may need to be adjusted to match the requirements of the application.

Overall, the parameters of the S&H oscillator are critical for determining its behavior and output characteristics. By adjusting these parameters appropriately, you can achieve the desired output characteristics for your specific application and requirements.

24> what is its algorithmic complexity?

The algorithmic complexity of a Sample and Hold (S&H) oscillator can vary depending on the specific implementation and the complexity of the input signal. In general, the computational complexity of an S&H oscillator is determined by the sample rate and the number of samples that are processed.

The basic algorithm for an S&H oscillator involves sampling the input signal at regular intervals determined by the clock rate, holding the sample value until the next sample is taken, and repeating this process to generate the output signal. This algorithm can be implemented using a variety of techniques, including analog circuits, digital signal processing algorithms, or programmable logic devices.

The computational complexity of an S&H oscillator can be affected by factors such as anti-aliasing filtering, oversampling, and the number of bits used to represent the input and output signals. In general, higher sample rates, more bits, and more complex signal processing algorithms will result in higher computational complexity.

Overall, the algorithmic complexity of an S&H oscillator is typically moderate, and can be managed using appropriate signal processing techniques and computational resources. By optimizing the design and implementation of the oscillator, it is possible to achieve high-quality output signals with reasonable computational resources.

25> i would like you to write with the voice of mark twain. could you teach me about the algorithm for this operator?

Certainly, I can do my best to write in the voice of Mark Twain! Here's a description of the algorithm for the Sample and Hold oscillator, as I imagine Twain might have written it:

"Well, now, friend, let me tell you a thing or two about this here Sample and Hold oscillator. It's a fancy piece of equipment, no doubt about that, but don't let its high-falutin' name fool you. At its heart, it's a simple algorithm that takes an input signal, samples it at regular intervals, and holds that value until the next sample is taken.

"Now, the devil's in the details, as they say, and the details of this algorithm can be a bit tricky. You see, the oscillator needs a clock signal to trigger the sampling and holding of the input signal. That clock signal needs to be stable and precise, or else you'll end up with a mess of noise and distortion.

"Once the clock signal is in place, the algorithm can do its thing. It samples the input signal at each clock cycle, holds that value until the next cycle, and then repeats the process. Simple, right?

"Well, it's not quite that simple. You see, there are all sorts of little tweaks and adjustments that you can make to the algorithm to get the best possible output signal. You can adjust the sample rate to balance accuracy and computational load, use anti-aliasing filters to prevent distortion and noise, and play with the hold time to get just the right amount of smoothing.

"All in all, the Sample and Hold oscillator is a nifty little algorithm that can do some truly impressive things. But like all good things in life, it takes a little bit of tinkering and tweaking to get it just right. So roll up your sleeves, friend, and let's get to work!"

Dependencies

~11–21MB
~298K SLoC