Constant CHOP

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ConstantCHOP 01.jpg


The Constant CHOP creates up to forty new constant-value channels. Each channel can be named and assigned a different value. To create a channel, simply enter a channel name in any left parameter in the 0, 10, 20 or 30 pages, then adjust the value to its right.

The CHOP interval (length of time) is one sample long by default (one sample at index 0 = frame 1). An interval range can be optionally set in the Channel page.

A simple Constant CHOP with no inputs is the most common use of the CHOP. However, the channels names and values can be set up by connecting any CHOP to its input and clicking the Snapshot Input button (Snap page). This allows you to get some channels from another CHOP and adjust them with sliders in the Constant CHOP.

The second input can be used to add offsets to the constant values. When the second input (Active) is greater than zero, any change to the first input will be added to the output of the CHOP. This is useful for adjusting Constant CHOP values from external input devices like a MIDI slider box. For example you can connect the mouse or a MIDI slider box to a Mouse In CHOP or MIDI In CHOP, and you can raise/lower the Constant CHOP values by holding the Active input On, while moving the mouse or sliders.

PythonIcon.png constantCHOP_Class

Parameters - 0, 10, 20 and 30 Pages

Each page contains fields for ten constant channels. The channel is created if there is a name in the Name field. You can enter channel name patterns in the Name field, so you can create many channels with the same value. For example, try entering:


in the first channel field instead of "chan1". See Pattern Expansion, Pattern Matching.

Parameters - Snap Page


The Constant CHOP can preset its channel names and values using the Snap page. We often want to grab some channels (Snapshot) and edit them later.

Snapshot Input - The optional first CHOP input on Constant is used when the Snapshot Input button is pressed. At this time, the channel names and values at the CHOP input at the current frame are used to initialize the channel names and values of the constant sliders.

To snap channels from other OPs, connect a Fetch CHOP to the Constant CHOP and hit Snapshot Input.

You can simulate the pressing of the Snapshot Input button from a script. To simulate the clicking of a CHOP dialog box button from a script use the opparm command:

 opparm -c opname channelname


 opparm -c /ch/ch1/constant1 snap

First Channel - The First Channel parameter is used to select a smaller set of the incoming channels. This is useful if the number of incoming channels is greater than the 40 channels the Constant CHOP can hold, and you must break it into several CHOPs.

Active Needs Current - This is used with the second input as described above, when you want to add a displacement to channels by using external devices or sources.

When Active Needs Current is On, the second CHOP input (the Active input) has an effect only if the Constant CHOP is the current CHOP.
When Active Needs Current is Off, the Constant CHOP is affected any time the Active input is on (greater than 0).
This is used by the Channel Editor when editing keyframes using CHOPs. An input device like a button in the Keyboard In CHOP or a MIDI keyboard can be fed to the Active input of many Constant CHOPs. Only the current CHOP will be affected if this option is On.

Parameters - Channel Page

Single Frame - Turn this Off to make constant channels that are longer than one frame.

Start / End /start /end - Start and end of the interval, expressed in Units (seconds, frames or samples). The parameters are expressed in the Units found on the Common page. To set the CHOP to be 100 samples long, Set Units to Samples, Single Frame Off and Start / End to 0 and 99.

Sample Rate /rate - The sample rate of the channels, in samples per second.

Extend Left / Extend Right /left /right - The left and right extend conditions (before/after range).

Default Value /defval - The default value used when one of the Extend parameters is set to Default Value.

Standard Options and Local Variables