Free equalization software for linux

Equalize plug-in does a histogram equalization of the image.

That is, it modifies the images histogram so that it is approximately horizontal, so that all intensity values cover about the same number of pixels in the image (i.e. the histogram is well-balanced).

BruteFIR is a software convolution engine, a program for applying long FIR filters to multi-channel digital audio, either offline or in realtime. BruteFIRs basic operation is specified through a configuration file, and filters, attenuation and delay can be changed in runtime through a simple command line interface.
The FIR filter algorithm used is an optimised frequency domain algorithm, partly implemented in hand-coded assembler, thus throughput is extremely high. In realtime, a standard computer can typically run more than 10 channels with more than 60000 filter taps each.
Through its highly modular design, things like adaptive filtering, signal generators and sample I/O are easily added, extended and modified, without the need to alter the program itself.
Main features:
- Designed for realtime filtering of HiFi quality digital audio
- Up to 256 inputs and 256 outputs
- Input/output provided by external modules for maximum flexibility
- Default I/O modules provide support for sound cards and files
- Access multiple I/O modules (= several sound cards / files) at the same time
- 8 - 24 bit audio at any rate supported by sound cards
- Easy-to-use C language API to create your own I/O modules, for example to support more file formats, other sound card APIs, or generate test signals
- Mix/copy channels before and/or after filtering
- Cascade filters or build complex filter networks
- Simple C language API to create logic modules, to add new functionality
- Create your own logic module, for example to do adaptive filtering
- Provided is a logic module which implements a CLI accessible through telnet to manage runtime settings, and a dynamic equalier.
- Toggle/change filter in runtime
- Alter attenuation for each individual input and output in runtime
- Alter delay for each individual input and output in runtime
- Filter length limited only by processor power and memory
- Typical filter lengths are in the range 2048 - 262144 taps
- Reasonable low I/O-delay (typically 200 ms)
- Fixed I/O-delay, thus possible to sample-align with other processors
- Cross-fade for seamless filter coefficient changes.
- Redithering of outputs (HP TPDF)
- Overflow protection and monitoring
- 32 or 64 bit floating point internal resolution.
- Supports multiple processors
A few examples of applications where BruteFIR could be a central component:
- Digital crossover filters
- Room equalisation
- Cross-talk cancellation
- Wavefield synthesis
- Auralisation
- Ambiophonics
- Ambisonics
Among these, room equalisation and auralisation needs the longest FIR filters in the common case. Many applications can do with quite short filters actually, but the thing is that you will probably not need to compromise on the filter lengths when you use BruteFIR, even when sample rates go up.
However, BruteFIR is pretty useless by itself, since it is only a FIR filter engine. It does not provide any filter coefficients, thus it is not a filter design program. Also, due to its relatively high I/O-delay, BruteFIR is most suited for applications when the input signal is not live.

Japa short from JACK and ALSA Perceptual Analyser is a perceptual or psychoacoustic audio spectrum analyser.

In contrast to JAAA, this is more an acoustical or musical tool than a purely technical one.

Possible uses include spectrum monitoring while mixing or mastering, evaluation of ambient noise, and (using pink noise), equalisation of PA systems.

JAPA allows you to measure two inputs at the same time, compare them, store them to memory and compare them to stored traces. It offers a number of resolutions, speeds, and various display options. The dual inputs and memories will find their way into future JAAA versions as well.

Display controls:

The controls below the spectrum window modify only the way things are presented, and not the actual measurement.

Range: Vertical display range, 20, 40, 60 or 80 dB. There are two scales. The one at the left is used for absolute displays. The one at the right always has 0 dB at half scale and is used when comparing two signals.

Scale: Controls the frequency scale. Grid lines are one octave apart, minor ticks are 1/3 octave. The default scale is logarithmic with ticks the standard 1/3 octave frequencies. There are two alternatives:

440 Hz log scale (click ) This follows the filter bandwidths, i.e. all filters will have the same width on the screen. The exact layout of this scale depends on the "warp factor" (see below).

Resp: The normal frequency response is flat in the sense that it will correctly indicate the level of a sine wave at all frequencies. The Prop setting adds a correction that is inversely proportional to the relative bandwidth of each filter. This will give a flat display when the input is pink noise.

Input controls:

There are two channels, called A and B. Each of them can be connected to one of four inputs, or switched off (this conserves CPU cycles - switching off the corresponding trace display does not).

Below the input selection is the gain control. Input gain can be set in steps of 5 dB. There are two more buttons:

Auto: Sets the gain based on the current signal level. This a momentary action.

Lnk: The second channels gain can be linked to the first for stereo operation. This includes the Auto function.

Analyser controls

Resol: Resolution of the filter bank. This sets the FFT size to 128, 256, or 512. The number of filters effectively used is almost equal to this number (japa interpolates between FFT bins to give correct amplitudes at all frequencies).

Warp: JAPA uses a warped FFT to analyse the spectrum. Frequency warping is done by replacing each delay element in the digital processing by an all-pass filter. This control allows you to set the warp factor, and this in turn determines how the filter bandwidths change as a function of the center frequency. You can see the warped scales by selecting the Warp option in the Scale display control. The default setting corresponds closely to the Bark scale. Higher values give more detail in the lower frequency range at the expense of the higher.

Speed: This controls the averaging filters that follow the spectrum analyser. The Low setting is mainly for noise measurement.

Memory store controls:

Each channel has a peak hold function. Note that this operates *after* the averaging done in the analyser and set by the Speed controls. There are two memories called X and Y. The current data for each channel can be stored to either memory. When the peak hold function is active, the current peak values are stored.

Note: the peak hold function and the two memories are reset when either the Resolution or Warp factor are changed. This may change in future versions.

Note: the gain controls are shown as part of the input blocks, but in reality the gain is applied only much later: when a trace is displayed or stored to memory. The result is that the peak hold function is not disturbed by changing the gain.

Trace display controls:

Three traces can be displayed at any time, and each row controls one of them. Options of the form A/B compare two inputs or memories. This means that the difference in dB between them is displayed rather than the actual levels.

xv is an interactive image manipulation program for the X Window System. It can operate on images in the GIF, JPEG, TIFF, PBM, PGM, PPM, XPM, X11 bitmap, Sun Rasterfile, Targa, RLE, RGB, BMP, PCX, FITS, and PM formats on all known types of X displays.
It can generate PostScript files, and if you have ghostscript (version 2.6 or above) installed on your machine, it can also display them.
Main features:
- display an image in a window on the screen
- display an image on the root window, in a variety of styles
- grab any rectangular portion of the screen and turn it into an image
- arbitrarily stretch, compress, rotate or flip the image
- crop or pad images
- view files as ASCII text or hexadecimal data
- magnify any portion of the image by any amount, up to the size of the screen
- determine pixel values and x,y coordinates in the image
- adjust image brightness and contrast with a gamma correction function
- apply different gamma functions to the Red, Green, and Blue color components, to correct for non-linear color response
- adjust global image saturation
- perform global hue remapping
- perform histogram equalization
- run a number of image-processing algorithms on any rectangular portion of the image
- edit an images colormap
- reduce the number of colors in an image
- dither in color and b/w
- crop off solid borders automatically
- convert image formats

Netsane is a script to easily configure multipath routing under Linux, allowing the use of multiple gateway links, and affording some measure of equalization (not true load balancing) across these links.
Multipath routing under Linux is not without caveats -- see Julian Anastasovs excellent site and patches for additional information and enhancements, as well as Christoph Simons notes on how to use more than one independent Internet connection.
Netsane is free software, released under the BSD License. You can download the latest release from the website.
Main features:
- easily configured multipath routing, including equalized route cycling
- options to add blackhole/null routes
- options to bind specific destinations to specific routes
- options to mark specific traffic to use specific routes (via iptables)