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This CHOP receives audio input from the analog audio ports or the digital port. It always outputs time sliced audio data. If you want to record the data, use a Record CHOP.
Receiving audio from an audio CD using a CD-ROM is not supported. Instead, feed the audio through the Audio-in port.
Selects the audio port to listen to.
Listens to the analog microphone port.
Listens to the analog line in port.
Listens to the digital port.
Selects mono, stereo, or 4 channel mode. 4 Channel mode is not available on all systems. This parameter also determines how many channels are created (1, 2 or 4).
Use Global Sample Rate
If on, audio is sampled at the system input sample rate. Otherwise, the next parameter allows you to change the system input sample rate.
This may disrupt other applications using the audio system. This parameter does not set the actual channel sample rate; that is set by the Sample Rate parameter in the Channel tab. These two sample rates can differ; the audio is resampled to the channel sample rate.
Input Sample Rate
The sample rate of the audio input system.
The number of seconds of audio to buffer at the input. Input audio will be delayed by this amount of time. A large buffer allows for slower cooking; if the buffer is too small, gaps and pops will be heard in the audio.
Each channel can be scaled separately by any factor.
This parameter controls the audio system hardware’s input attenuation, which corresponds to the “record level” of a tape recorder. 0 is the lowest recording level, and 1 is the highest recording level. If you notice audio is being clipped at +-1, lower this value.
Channel 1-4 Name
The names of the audio channels.
The sample rate of the audio channels. This may be different from the audio input’s sample rate; the input audio will be resampled to the CHOP’s sample rate.
Extend Left, Right
The extend conditions for the audio channels.
The default value for the 'Default Value' extend condition.
Some of these parameters may not be available on all CHOP nodes.
To determine which channels get affected, some CHOPs have a scope string. Patterns can be used in the scope, for example
* (match all), and
? (match single character).
The following are examples of possible channel name matching options:
Matches a single channel name.
chan3 tx ty tz
Matches four channel names, separated by spaces.
Matches each channel that starts with
Matches each channel that has
foot in it.
? matches a single character.
t? matches two-character channels starting with t.
Matches number ranges giving
[xyz]matches three characters, giving channels
Sample Rate Match
The Sample Rate Match Options handle cases where multiple input CHOPs’ sample rates are different.
Resample At First Input’s Rate
Use rate of first input to resample others.
Resample At Maximum Rate
Resample to highest sample rate.
Resample At Minimum Rate
Resample to the lowest sample rate.
Error if Rates Differ
Does not accept conflicting sample rates.
The units for which time parameters are specified.
For example, you can specify the amount of time a lag should last for in seconds (default), frames (at the Houdini FPS), or samples (in the CHOP’s sample rate).
When you change the Units parameter, it does not convert the existing parameters to the new units.
Time Slicing is a feature which boosts cooking performance and reduces memory usage. Traditionally, CHOPs calculate the channel over its entire frame range. If the channel does need to be evaluated every frame, then cooking the entire range of the channel is unnecessary. It is more efficient to calculate only the fraction of the channel that is needed. This fraction is known as a Time Slice.
Causes the memory consumed by a CHOP to be released after it is cooked and the data passed to the next CHOP.
The Export prefix is prepended to CHOP channel names to determine where to export to.
For example, if the CHOP channel was named
geo1:tx, and the prefix was
/obj, the channel would be exported to
You can leave the Export Prefix blank, but then your CHOP track names need to be absolute paths, such as
Every CHOP has this option. Each CHOP gets a default color assigned for display in the Graph port, but you can override the color in the Common page under Graph Color. There are 36 RGB color combinations in the Palette.
Graph Color Step
When the graph displays the animation curves and a CHOP has two or more channels, this defines the difference in color from one channel to the next, giving a rainbow spectrum of colors.