DeFX Plug-in

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DeFX Multi-effects processor Plug-in for XMMS

DeFX effects description and samples
The current version of DeFX includes 6 effects that can be activated simultaneously and configured separately. For each effect I've included a little demo (22Khz mono) using an extract of one Dream Theater's song called New Millenium.
After each description you will find a link to donwload the sample file with the effect applied to it. But, before that, you must download the sample file without effects to note the difference.

1. Chorus
This effect is mostly used on voices or basses. It adds an aditional voice, so you hear like there are two sound sources. Most people have difficulty to recognize it, but most musicians will appreciate it.
The chorus effect uses a varying delay that make the second voice sound somewhat different from the main voice. An additional delay is added to the varying delay to avoid flanging.
There are seven parameters for chorus.
  1. The first is the AMOUNT. You can select how much effect is applied to your sound.
  2. The second is the LFO (Low Frequency Oscillator) waveform used for the varying delay. Select between triangular, sinusoidal and exponential.
  3. The RATE of the varying delay, left values (lowest) give a slow variation.
  4. The DEPTH of the variation, higher values give a wide variation.
  5. With AMOUNT you can select how much effect is applied to your sound.
  6. FEEDBACK tells how much of the output signal is sended to the input. Try high settings of this parameter to increase the presence of the effect
  7. The STEREO option makes the left channel to be out if phase from the right, so you have different chorus on left and right.

Hear the second voice: Download sample file with chorus

2. Flange
This is another delay based effect. Its use is more common, surely you have heard it before. It's hard to descibe how it sounds, but you can do the following experiment: take an empty cup of tea (make sure it's empty :) and put it over one ear, like if you would hear the void. That sound is similar to flange.
Flange uses the same algorithm than chorus except that the additional delay is removed, so you can easily have amplifications and cancelations of the original waveform.
The parameters of flange are the same of chorus.

Feel the waves: Download sample file with flange

3. Phaser
Some people tend to confuse about this effect. It's very similar to flanger but with a really distinctive sound. It's a varying filter wich make some frequency cancelations and amplifications. It's very weird at hi feedback settings!!

There is no sample for this effect yet

4. Voice Removal
This is one of the simplest and most popular effect. It removes the mono channel on stereo sounds. Most singers record their voice on the mono channel, so, if you remove it, you can remove its voice.
The bad thing is that the voice cannot be removed if it is not recorded at the mono channel, another bad thing is that any other sound that lies in the mono channel will be removed also. I figured this effect a long time ago, while I was pluging my phones to the radio, there was a position when the signal turns to mono and some of the vocals and another sounds were removed, that make me think about this way to do it. But nobody believed me that it could be so easy!!! (hey CesarHM).
To remove the center channel I add the inverted left to the right and vice-versa, using that, all the sound that is common to both channels is cancelled out!.
I mean the folowing. If L is the left channel and R the right, the sound is in the form of:

L = X * Z
R = Y + Z

Where X is the Left component, Y the right and Z the mono component. Them Voice removal do:
VR = (L-R) = (X+Z) - (Y+Z) = X-Y

With the parameter AMOUNT you indicate the volume of the mono channel, higher values give you the lowest volume.

In the sample, you will not hear the center channel, that includes bass and main drums, while the funky guitar (right channel) and additional drums (left channel) are amplified. Download it

5. Reverberation
This effect tries to simulate the sound that is reflected by the walls or objects that sorround the sound source. For example, if you clap your hands on an empty hangar, its not the same that doing it at you bedroom, the first will sound 'fatter' than the second.
My reverb uses a simplified algorithm (4 combos, no ER) to reduce the amount of CPU power needed. Previous versions of DeFX also used floating point math, but the poor performance obtained on some CPU's (like AMD K6), make me rewrite the routine to use fixed point math. That reduced the CPU use from 70% to 30% in my P200MMX. You can change 3 parameters:
  1. The LENGTH parameter change the time reverb takes to decay, higher values give you a long decay time. If you can simulate large rooms, use high values.
  2. You can change the amount of reverb added to the original singal using the LEVEL parameter.
  3. The INPUT parameter change the amount of original signal used to produce the resulting signal. If you use low values you will hear like you were far away from the sound source.
Take care while using higher values for the three parameters, you can easily get a clipped output. To avoid this, if you want a lot of reverb with no clip, try lower values of the INPUT parameter.

Now we are playing on a bigger room: Download sample file with reverb

6. Balance
This another simple effect. It lets you hear any of the two channels (left and right) on both ears. I made it to transcribe some songs where keyboards were recorded on left and guitars on right. Hope you find an use to it too:) The only parameter you change is the amount of presence of one channel on both speakers. On the Center position you have a normal output.

The file now is splitted on left and right channel. Notice that left channels contains some drums while right channel contains the guitar: Download left channel of sample file, download right channel of sample file