Lib.rs

Rust crate for a dual delay effect in the Surge synthesizer system

The surgefx-dualdelay crate provides a dual delay effect, which is one of the subcomponents of the Surge synthesizer system. This effect is designed to create stereo delay lines with independent control over various parameters, such as delay time, feedback, crossfeed, filtering, and panning. The crate contains the necessary functions and structures to initialize, process, and control the dual delay effect.

The mathematical foundation of the dual delay effect involves the manipulation of discrete-time audio signals. The effect uses two separate delay lines to process the left and right channels independently. Given an input signal 𝑥(𝑛), the output signal 𝑦(𝑛) for each channel is computed using a combination of delay time 𝑇, feedback 𝐹, crossfeed 𝐶, filtering 𝐻(𝑧), and panning 𝑃:

𝑦(𝑛) = 𝑃(𝑥(𝑛) + 𝐶(𝑥(𝑛 - 𝑇) + 𝐹𝑦(𝑛 - 𝑇))) * 𝐻(𝑧)

Tokens and their mathematical associations:

• control_group, control_type, default_value, max_value, min_value, modulateable, moverate, value_type: These tokens are used to define and control the parameters of the dual delay effect, such as delay time, feedback, crossfeed, filtering, and panning.

• update: This function updates the internal state of the dual delay effect, recalculating delay times, filter coefficients, and other parameters based on the current control values.

• do_dualdelay_block: This function processes the input audio signal using the dual delay effect, computing the output signal according to the current delay times, feedback, crossfeed, filtering, and panning settings.

• process_time: This function processes the delay times for each channel, ensuring that they are within the allowed range and taking any modulation or tempo-syncing into account.

• dual_delay_smoke, clear_buffers, init, instantize_all, clear_scratch_buffers: These functions are used to initialize and reset the internal state of the dual delay effect, including clearing audio buffers, setting initial parameter values, and instantiating filters.

• do_crossfeed, do_feedback, do_filters, do_mid_side, do_mix, do_pan, do_softclip: These functions are responsible for implementing the various processing stages of the dual delay effect, such as crossfeeding between channels, applying feedback, filtering the delayed signal, and adjusting the stereo image.

• maybe_instantize_all, process, process_only_control, update_wpos: These functions handle various aspects of processing the audio signal, such as updating the write position in the delay buffer and applying parameter changes in real-time.

• DualDelay, dualdelay_set_buffer: These structures and functions define the main dual delay effect object and its associated methods, including setting the audio buffer to be used for processing.

22> thanks! could you show me some in depth block diagrams about how the subcomponents of this effect fit together?

Certainly! Here's an in-depth block diagram illustrating the signal flow and subcomponents of a dual delay effect:

Input Signal (L, R) ─┐
                     ├─┬──[Panner]───┐
                     │ ├─[Crossfeed]─┼─┐
                     │ └─[Feedback]──┘ │
                     │                 ├─[Delay Line L]─┬─[Filter L]─┬─[Softclip L]─┬─[Output Gain L]──┐
                     ├─────────────────┤                 │            │             │                  ├─ Output Signal (L, R)
                     │                 ├─[Delay Line R]─┼─[Filter R]─┼─[Softclip R]─┼─[Output Gain R]──┘
                     ├─┬──[Panner]───┐ │                 │            │             │
                     │ ├─[Crossfeed]─┼─┘
                     └─┴─[Feedback]──┘

1. Input Signal (L, R): The left and right channels of the input signal enter the dual delay effect.

2. Panner: The panner adjusts the stereo balance of the input signal before it is sent to the delay lines.

3. Crossfeed: The crossfeed subcomponent takes a portion of the input signal from one channel and adds it to the other channel, creating a more complex stereo image. The amount of crossfeed can be controlled by the user.

4. Feedback: The feedback subcomponent takes a portion of the delayed signal from the output of each delay line and feeds it back into the input of the corresponding delay line, creating a repeating echo effect. The amount of feedback can be controlled by the user.

5. Delay Line L & R: These are the main delay lines for the left and right channels. They store the audio signal and provide a time-varying delay, controlled by the delay time parameter.

6. Filter L & R: After the delay lines, the signal passes through filters for each channel. These filters can be used to shape the frequency content of the delayed signal, such as low-pass, high-pass, or band-pass filters. The filter settings can be controlled by the user.

7. Softclip L & R: The softclip subcomponents apply a soft-clipping non-linear function to the delayed and filtered signal, adding harmonic distortion and preventing excessive peaks in the output signal.

8. Output Gain L & R: The output gain stages adjust the overall level of the delayed signal before it is combined with the dry signal and sent to the output.

9. Output Signal (L, R): The processed left and right channels of the delayed signal are combined with the original input signal, creating the final output signal with the desired dual delay effect.

The diagram above shows the main subcomponents of a dual delay effect and how they are connected to create the desired stereo delay processing. The specific implementations of these subcomponents may vary depending on the desired sound and functionality, but the general signal flow remains the same.

23> thanks -- how are these modules parametrized? which handles can the user adjust at runtime?

In a dual delay effect, there are several parameters that users can adjust to control the sound and behavior of the effect. Here is a list of common parameters that can be adjusted at runtime:

1. Delay Time (L & R): The delay time determines the length of the delay lines for each channel. Users can set different delay times for the left and right channels to create a more complex stereo image. In some implementations, users can also synchronize the delay times to the tempo of the music.

2. Feedback (L & R): The feedback parameter controls the amount of signal fed back from the output of each delay line to its input. By adjusting the feedback, users can create more or fewer repeats of the delayed signal.

3. Crossfeed: The crossfeed parameter controls the amount of signal from one channel that is added to the other channel before entering the delay lines. This can be used to create a more complex and spacious stereo image.

4. Filter (L & R): The filter parameters control the characteristics of the filters applied to the output of each delay line. Users can adjust the filter type (low-pass, high-pass, band-pass, etc.), the filter cutoff frequency, and the filter resonance.

5. Soft Clipping (L & R): The soft clipping parameters control the amount of distortion applied to the delayed signal after filtering. Users can adjust the level of soft clipping to add warmth or saturation to the sound.

6. Output Gain (L & R): The output gain parameters control the level of the processed delayed signal before it is combined with the dry signal and sent to the output. This can be used to balance the levels of the dry and wet signals.

7. Dry/Wet Mix: The dry/wet mix parameter controls the balance between the unprocessed input signal (dry) and the processed delayed signal (wet). Users can adjust this parameter to achieve the desired blend of the original and delayed signals.

8. Panning (L & R): The panning parameters control the stereo positioning of the input signal before it enters the delay lines. Users can adjust the panning to create a wider or narrower stereo image.

These parameters allow users to shape the sound and behavior of the dual delay effect to suit their needs. In a well-designed effect implementation, these parameters can be adjusted in real-time, providing users with a high degree of control and flexibility.

24> could you describe a dozen different descriptions of effects produced by this processor at different parameter settings?

Certainly! Here are twelve different descriptions of effects produced by the dual delay processor with different parameter settings:

1. Basic Stereo Delay: Set equal delay times for both left and right channels, moderate feedback, and a balanced dry/wet mix. This results in a simple stereo echo effect, with the delay repeats equally spaced in both channels.

2. Ping Pong Delay: Set different delay times for the left and right channels and high crossfeed. The delayed signal will bounce back and forth between the left and right speakers, creating a ping pong effect.

3. Slapback Echo: Set short delay times for both channels, low feedback, and a moderate dry/wet mix. This creates a slapback echo, often used in rockabilly and early rock 'n' roll music.

4. Ambient Delay: Set long delay times, high feedback, low-pass filters with a low cutoff frequency, and a high wet mix. This creates a spacious, atmospheric effect, with the delays blending into the background.

5. Dub-style Delay: Set medium to long delay times, high feedback, low-pass filters with a moderate cutoff frequency, and a high wet mix. This results in a warm, analog-style delay effect commonly used in dub and reggae music.

6. Shimmer Delay: Set long delay times, high feedback, and apply a pitch-shifting effect (e.g., one octave up) to the feedback loop. This creates a shimmering, ethereal sound, often used in ambient and experimental music.

7. Filtered Rhythmic Delay: Set different delay times for the left and right channels, with the delay times synced to the tempo of the music. Use band-pass filters with a narrow bandwidth and modulate the filter cutoff frequency in time with the music. This creates a rhythmic, pulsating delay effect.

8. Distorted Delay: Set medium delay times, moderate feedback, and high soft clipping levels. This creates a delay effect with a gritty, distorted character.

9. Spatial Widener: Set very short delay times (e.g., 10-30 ms) for both channels, low feedback, and a moderate dry/wet mix. This creates a subtle widening effect, enhancing the stereo image of the input signal.

10. Reverse Delay: Reverse the delayed signal before feeding it back into the input. This creates a reverse delay effect, often used for experimental or psychedelic sounds.

11. Chorus-like Delay: Set very short delay times (e.g., 20-50 ms), low feedback, and modulate the delay time with a slow LFO. This creates a chorus-like effect, adding depth and movement to the sound.

12. Freeze Delay: Set very long delay times, maximum feedback, and a high wet mix. By momentarily sending a signal into the delay lines, you can create a "frozen" sound that sustains indefinitely, creating a drone or pad-like effect.

These are just a few examples of the wide range of effects that can be achieved using a dual delay processor. By adjusting the parameters and combining different settings, you can create an almost limitless variety of delay-based soundscapes.

25> thanks, i like these descriptions -- could you do a dozen more?

Sure! Here are twelve more descriptions of effects produced by the dual delay processor with different parameter settings:

1. Glitchy Delay: Set short, unsynchronized delay times for both channels, high feedback, and apply a bitcrusher or sample rate reducer to the feedback loop. This creates a glitchy, lo-fi delay effect.

2. Multi-Tap Delay: Configure multiple delay lines with different delay times and feedback levels for each channel, and mix them together. This creates a complex, multi-tap delay effect that can add texture and depth to the sound.

3. Gated Delay: Apply a noise gate or expander to the delayed signal, with a threshold set to only allow louder delay repeats to pass through. This creates a dynamic delay effect where the echoes are only audible when the input signal is loud enough.

4. Swirling Delay: Modulate the delay time, filter cutoff frequency, and/or panning of the delay lines with different LFOs or envelope followers. This creates a swirling, evolving delay effect with a lot of movement.

5. Granular Delay: Set very short delay times (e.g., 1-10 ms), high feedback, and use a granular synthesis engine to process the delay lines. This creates a granular delay effect, where the input signal is broken into small grains and rearranged in time and space.

6. Dynamic Delay: Use an envelope follower or sidechain compression to control the delay level or feedback based on the input signal's amplitude. This creates a dynamic delay effect, where the echoes become more prominent when the input signal is quieter.

7. Pitch-Shifting Delay: Apply different pitch-shifting intervals to the left and right delay lines, such as a perfect fifth or an octave. This creates a harmonically rich delay effect, adding melodic or harmonic interest to the sound.

8. Resonant Delay: Set high feedback levels and use resonant low-pass or band-pass filters in the feedback loop. This creates a resonant delay effect, where the echoes emphasize specific frequencies and produce a ringing or resonant sound.

9. Flanger-like Delay: Set very short delay times (e.g., 5-20 ms), low feedback, and modulate the delay time with a slow LFO. This creates a flanger-like effect, with a characteristic "whooshing" or "jet plane" sound.

10. Ducking Delay: Use a sidechain compressor or envelope follower to reduce the delay level or mix when the input signal is playing. This creates a ducking delay effect, where the echoes are pushed back in the mix when the input signal is present, helping to maintain clarity and prevent clutter.

11. Diffused Delay: Use multiple delay lines with slightly different delay times and feedback levels, and process the outputs with a diffusion network or reverb algorithm. This creates a diffused delay effect, where the echoes are smeared and blended together, producing a more diffuse and spacious sound.

12. Comb Filter Delay: Set very short delay times (e.g., 1-10 ms), high feedback, and no filtering. This creates a comb filter delay effect, where the input signal is combined with a slightly delayed copy, creating a series of notches in the frequency spectrum and adding a metallic or "tuned" quality to the sound.

These additional examples showcase the versatility of a dual delay processor. By experimenting with different parameter settings and combinations, you can create a vast array of unique and interesting delay effects.

26> how do we prevent unwanted artifacts when engineering this signal processor?

To prevent unwanted artifacts when engineering a dual delay signal processor, there are several aspects you need to consider and address:

1. Aliasing: When working with digital signal processing, aliasing can occur due to the discrete nature of the process. To minimize aliasing, use oversampling (processing the signal at a higher sample rate) and apply anti-aliasing filters before downsampling back to the original sample rate.

2. Noise: Ensure that the input signal is clean and free from noise, as any noise present will be amplified by the delay process, especially with high feedback settings. You can use noise reduction techniques or low-pass filters to remove unwanted noise from the input signal.

3. Feedback instability: When using high feedback levels, the delay can quickly become unstable and produce unwanted artifacts or oscillations. To prevent this, apply a limiter or soft-clipper in the feedback loop to control the amplitude and ensure stability.

4. Phase issues: When using multiple delay lines, phase issues can arise, causing cancellation or reinforcement of certain frequencies. To minimize phase issues, use different delay times for each channel or apply all-pass filters to adjust the phase response without affecting the amplitude.

5. Clicks and pops: Abrupt changes in delay times or parameter settings can cause clicks and pops in the output signal. To prevent this, use interpolation, crossfading, or smoothing techniques to ensure smooth transitions between parameter changes.

6. Denormalization: In digital signal processing, very small floating-point numbers can cause performance issues and create artifacts. To prevent this, use denormalization techniques, such as adding a small offset to the signal or using specialized functions that handle denormal numbers efficiently.

7. Latency: When designing a real-time audio processor, it's crucial to minimize latency to ensure a responsive and natural-sounding effect. Optimize your code for performance and, if necessary, use parallel processing or look-ahead techniques to reduce latency.

8. Parameter modulation: When modulating parameters, such as delay time or filter cutoff frequency, use smooth modulation sources like low-frequency oscillators (LFOs) or envelopes. Abrupt changes in modulation can cause artifacts and produce unnatural-sounding results.

9. Filter design: When using filters in the delay processor, ensure that they are designed to minimize artifacts like ringing, aliasing, or phase distortion. Choose appropriate filter types (e.g., Butterworth, Chebyshev, or elliptic filters) based on the desired characteristics and performance requirements.

10. Signal headroom: Ensure that there is enough headroom in the processing chain to prevent clipping and distortion. Use gain staging techniques to maintain an appropriate signal level throughout the processor.

By addressing these potential issues during the design and engineering of a dual delay signal processor, you can minimize unwanted artifacts and ensure a clean, high-quality output.

27> what else can you tell me about dual delay? what can you show me?

A dual delay is a versatile audio effect that processes an input signal by independently delaying the left and right channels. This creates a stereo effect that can add depth, width, and space to a sound. Here are some additional insights and visualizations related to dual delay:

Configurations and variations:

Dual delay can be used in various configurations, such as parallel or serial processing. In a parallel configuration, the left and right channels are processed independently, while in a serial configuration, one channel's output is fed into the other channel's input, creating a more complex, cascading delay effect.

Synchronization:

You can synchronize the delay times to the tempo of a song, using musical note values (e.g., quarter notes, eighth notes) to define the delay times. This helps create rhythmic coherence between the delay effect and the rest of the music. You can also use unsynchronized delay times to create more experimental or unpredictable effects.

Modulation:

Modulating the delay time, filter cutoff frequency, feedback, or other parameters with LFOs or envelope followers can create dynamic and evolving delay effects. For example, you can create a chorus or flanger effect by modulating the delay time with a slow LFO.

Visualization:

Here is a simple block diagram of a dual delay processor:

   Input Signal
        |
        V
  ┌─────┴─────┐
  │  Left Delay ├──────┐
  └────────────┘      |
                       V
                  Wet/Dry Mix
                       |
                       V
  ┌─────┴─────┐      Output
  │ Right Delay ├──────┘
  └────────────┘

This diagram shows the basic structure of a dual delay, with separate delay lines for the left and right channels. The wet/dry mix control adjusts the balance between the original (dry) signal and the delayed (wet) signal before output.

Ping-pong delay:

A common variation of the dual delay is the ping-pong delay, where the output of one channel is fed into the input of the other channel, creating a bouncing effect between the left and right speakers. This can add even more stereo width and depth to the sound.

Creative uses:

Dual delay can be used creatively to enhance a variety of sounds, such as adding space and depth to vocals, creating rhythmic patterns for guitars or synths, or adding a sense of movement and interest to pads and ambient textures. By experimenting with different delay times, feedback levels, modulation, and filtering, you can create a wide range of unique and interesting audio effects.

Overall, dual delay is a powerful and versatile audio effect that can be used in a variety of ways to enhance and enrich your sound. By understanding the underlying concepts and exploring different configurations and parameter settings, you can unlock its full potential and create unique, captivating audio experiences.

28> how do we prevent the delayed audio from phasing with the original source and causing unwanted interference?

To prevent the delayed audio from phasing with the original source and causing unwanted interference, there are several techniques you can apply:

1. Use different delay times for left and right channels: By using different delay times for each channel, you can minimize the chance of phase cancellation between the original and delayed signals. This will create a more spacious stereo image and can help reduce phase-related issues.

2. Apply filters to the delayed signal: By using filters, such as low-pass or high-pass filters, you can remove certain frequency components from the delayed signal. This can help reduce the chances of phase interference with the original signal. Additionally, you can use band-pass or band-reject filters to target specific frequency ranges.

3. Modulate delay times: By slightly modulating the delay times with a low-frequency oscillator (LFO), you can create a constantly shifting phase relationship between the original and delayed signals. This can help prevent static phase cancellation and add a sense of motion and depth to the sound.

4. Utilize Haas effect: The Haas effect, also known as the precedence effect, states that when two similar sounds arrive at the listener's ears within approximately 40 milliseconds of each other, the listener perceives them as a single sound coming from the direction of the first-arriving sound. By setting the delay times shorter than 40 milliseconds, you can create a sense of spatial localization without causing significant phase interference.

5. Adjust the feedback: Reducing the amount of feedback in the delay can help minimize the buildup of phase interference over time. Lower feedback settings will result in fewer delay repeats, which can reduce the chance of phase issues.

6. Experiment with delay algorithms: Different delay algorithms, such as tape, digital, or analog delay, can have varying effects on phase relationships. Experiment with different algorithms to find the one that best suits your needs and minimizes phase-related issues.

7. Use mid/side processing: By processing the mid (mono) and side (stereo) components of the signal separately, you can control the phase relationship between the original and delayed signals more effectively. For example, you can apply the delay only to the side signal to preserve the phase coherence of the original mono signal.

By using these techniques, you can minimize the chance of phase interference between the original and delayed signals, resulting in a cleaner and more spacious sound. Experimenting with different settings and processing techniques will help you find the best balance between preserving the original signal's integrity and achieving the desired delay effect.