This section briefly describes the various modules that come with GNUsound. These modules are available via the Tools menu. They all need an active selection to operate on.
This module amplifies or attenuates the signal. The primary envelope determines by how much the signal is attenuates.
This module zeroes those parts of the signal that are below a certain treshold for a given duration. The Delete option toggles whether the relevant section in the signal should be zeroed or deleted. The Gang tracks option toggles whether each track should be processed separately, or whether the intersection from all selected tracks should be used. Finally the Invert option inverts the meaning of the operation, selecting noise rather than silence.
This module shrinks the selection to the nearest zero points. This is mostly useful to prevent clicks in a looped sample.
This module implements a very simple bandpass filter. It was lifted from the sox audio tool distribution mostly as a curiosity. Much better and more versatile filters are available through the LADSPA plugins module.
This module removes some digital clipping artifacts from material that was recorded too loud. It is very stupid and does not have any tricks up its sleeve whatsoever (not even interpolation) but still I find it works rather well.
This module implements a simple digital delay. The Duration parameter controls the duration of each delay in the time units as given by the time control bar. This parameter is controlled by the primary envelope. The Times parameter controls the number of delays. The Decay parameters controls the rate of decay. This parameter is controlled by the auxiliary envelope.
This module implements support for the Linux Audio Developers Simple Plugin Architecture. You must install some LADSPA plugins to use this module, these can be obtained from http://www.ladspa.org. Before starting GNUsound make sure the LADSPA_PATH environment variable points to the location where your plugins are installed. If the LADSPA_PATH is not defined then GNUsound will search /usr/local/lib/ladspa for plugins.
The interface for this module consists of a window that is split in two halves: the left half contains the available plugins, and the right half contains the parameters for the selected plugin.
When the list of plugins is active, you can press a key to jump to the first plugin whose name starts with that letter.
The right half of the window has sliders to set the parameters for the plugin. You can use the Env1 and Env2 buttons to assign a parameter to the corresponding envelope. The envelope modifies the parameter value in the following way: if the envelope value is 0, then the parameter value is the parameter value set by the user. If the envelope value is between 0 and 1, then the parameter value is between the user selected parameter value and the maximum parameter value. Finally if the envelope value is between 0 and -1, then the parameter value is between the user selected parameter value and the minimum parameter value.
An envelope assigned to a LADSPA parameter does not change that parameter every sample; rather the signal is processed in blocks and the envelope value applies to an entire block. The size of these blocks can be changed in the configuration file (the ladspa_segment_time parameter). The default value for this parameter is 0.1 seconds.
This module implements a very simple lowpass filter. It was lifted from the web and is included mostly as a curiosity. Much better and more versatile filters are available through the LADSPA plugins module.
This module mixes the signal from the second selected track into the first. The primary envelopes on the selected tracks specify the contribution of each track to the final signal.
This module determines the peak amplitude of the selected track(s) and proceeds to amplify the tracks so that the signal amplitude is maximal. If you select a multiple tracks, then the global peak for the selected tracks is used as a reference point.
This module changes the sampling rate of the selected audio. Depending on whether you have libsamplerate installed it offers one or more methods of doing so, with varying quality/speed tradeoffs. The primary envelope controls the rate.