# Envelope CHOP

## Summary

The Envelope CHOP outputs the maximum amplitude in the vicinity of each sample of the input. It takes the absolute value of the input, and uses a sliding window of a number of samples to find the maximum amplitude near each sample.

Tip: The loudness levels of an audio track can be kept roughly constant by computing an envelope of the audio with a wide window, and then passing the original audio and the envelope to a Math CHOP and selecting Combine CHOPs - Divide. This will make the amplitude approximately 1.

## Parameters - Envelope Page

Type method - - The two methods of calculating the envelope:

• Exponential Decay exp - For each sample, the value is compared to the previous sample. If it is greater than the previous, the value of the envelope is equal to the value of that sample, and that sample is stored as the current peak. If it is less than, the value of the envelope decays exponentially from the last peak to the current value (as more samples pass that are smaller than the peak, the envelope decays toward the waveform). Pros: Always encloses the data. Cons: Slope can be discontinuous, making the output look bumpy.
• Local Maximum Window window - The channel is separated into windows of N samples determined by the Envelope Width. In each window, the maximum amplitude (or power) is found. The maximum value of the window is placed as a data point in the center of the window, and these points are cubically interpolated together to form the output envelope. Pros: Produces Good shapes. Cons: Signal sometimes jumps outside the envelope. The signal is quantized, so pulses can be off by as much as N/2.

Envelope Bounds bounds - -

• Magnitude mag -
• Signal Power power -
• Maximum Values min -
• Minimum Values max -

Envelope Width width - The width of the window to use in the envelope calculation. Adjust this width to capture as many features of the input as needed. It is expressed in Units.

Envelope Width Unit widthunit - -

Interpolate interp - -

• None none -
• Linear linear -
• Cubic cubic -

Normalize Power Envelope norm - Keeps the total power in the signal constant when adjusting the Envelope Width.

Resample Envelope resample -

Sample Rate samplerate -

## Parameters - Common Page

Time Slice timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.

Scope scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.

Sample Rate Match srselect - - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.

• Resample At First Input's Rate first - Use rate of first input to resample others.
• Resample At Maximum Rate max - Resample to the highest sample rate.
• Resample At Minimum Rate min - Resample to the lowest sample rate.
• Error If Rates Differ err - Doesn't accept conflicting sample rates.

Export Method exportmethod - - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.

• DAT Table by Index datindex - Uses the docked DAT table and references the channel via the index of the channel in the CHOP.
• DAT Table by Name datname - Uses the docked DAT table and references the channel via the name of the channel in the CHOP.
• Channel Name is Path:Parameter autoname - The channel is the full destination of where to export to, such has geo1/transform1:tx.

Export Root autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.

Export Table exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).

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An Operator Family which operate on Channels (a series of numbers) which are used for animation, audio, mathematics, simulation, logic, UI construction, and many other applications.

Strictly refers to a window in Microsoft Windows. User-created windows are made with Panels inside Window Components, aside from the TouchDesigner editor window and its dialogs.

samples-per-second of a CHOP. Each CHOP in your network has a sample rate, whether it is used or not. The overall timeline has a "frame rate", which is the number of animation frames per second, generally your monitor display frequency.

A Time Slice is the time from the last cook frame to the current cook frame. In CHOPs it is the set of short channels that only contain the CHOP channels' samples between the last and the current cook frame.

A parameter in most CHOPs that restricts which channels of that CHOP will be affected. Normally all channels of a CHOP are affected by the operator.

Exporting is the connection of CHOP channels to parameters of operators. The output of each exporting CHOP is one or more channels, active only while the CHOP Viewer is on. The current value of a channel can be exported to a parameter of any operator, overriding that parameter's value. See Parameter.

An Operator Family that manipulates text strings: multi-line text or tables. Multi-line text is often a command Script, but can be any multi-line text. Tables are rows and columns of cells, each containing a text string.

The location of an operator within the TouchDesigner environment, for example, /geo1/torus1, a node called torus1 in a component called geo1. The path / is called Root. To refer instead to a filesystem folder, directory, disk file or http: address, see Folder.

Parameters in TouchDesigner are an operator's settings (numbers, menus, flags, strings, paths) which the user can alter. Parameters for any operator can be opened by right-clicking on the operator and selecting "Parameters..." A currently selected operator's parameters can be viewed in a Network Editor by pressing the keyboard shortcut 'p'.

TouchDesigner is a hierarchy of components. "root" is the top-most network in the hierarchy. The Path is simply /. A typical path is /project1/moviein1.