Orinj Compressor

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Orinj version 3.0.0

The Orinj Compressor automatically adjusts the amplitude of the incoming signal, usually to bring together quieter and louder parts of the signal (compressing) or, more rarely, to further separate quieter and louder parts of the signal (expanding). A compressor has many uses:

  • Automatically bringing louder and quieter parts of the signal together can be used on vocals to ensure that vocals do not overwhelm certain parts of the song while getting lost in other parts of the song.
  • Decreasing the amplitude of the ring of drum hits ensures that the initial drum hit is sharper.
  • Quickly decreasing the amplitude of high frequencies in vocals automatically when these high frequencies become notable can be used for de-essing – removing the "s" sounds from the vocals.

This particular compressor works on three different frequency bands separately. Bass frequencies (below 300 Hz) are treated separately from mid-range frequencies (between 300 Hz and 1500 Hz) and both of these frequency intervals are treated separately from high frequencies (over 1500 Hz). In many uses of the compressor, this is not necessary. For de-essing, however, it is useful to be able to separate and act only on high frequencies.

See Compressor / expander (of dynamics) for more information on how compressor works. As a quick example, consider a compressor with a threshold of -30 dB, a compression ratio above -30 dB of 2:1, and a compression / expansion ratio of 1:1 below -30 dB. If the signal has amplitude of -25 dB, it is above the threshold by 5 dB. This difference between the signal and the threshold of 5 will be compressed with the ratio 2:1 to a difference of 2.5 dB. This means that the output signal will be at -27.5 dB. If an input signal has the amplitude -35 dB, it is 5 dB below the threshold. Since the compression / expansion ratio below the threshold is 1:1, this signal will remain unchanged. Thus, this specific example compressor makes loud signals less loud while leaving quiet signals the same.

Compressors have other parameters, such as attacks and releases. These are explained below. In addition, there are two types of compressors – one that acts on the peak amplitude of the signal (i.e., the actual value of the signal at a specific point in time) and one that acts on the amplitude envelope of the signal (i.e., a measure of the power of the signal over an interval of time, independent of what the peak value of the signal at the specific time is; see Hilbert transform for more information on how this amplitude may be computed). This compressor is of the second type.

Using the Orinj Compressor

The Orinj Compressor can be added to tracks in the multitrack session view, tracks in the loop building view, and to waves in the single wave view. In the multitrack session view and in the loop building view, first select the track to which you want to add the effect. In all these views, click on Effect, Dynamics, and then on Orinj Compressor in the Orinj menu. You will see the following dialog.

The Orinj Compressor dialog

When this dialog becomes visible, the Orinj Compressor has been added. Adjust the compressor parameters in the dialog – these parameters are described below – and click on Close.

Orinj Compressor parameters

See Orinj Effects for an explanation of the Title, Track, Presets, and Bypass controls. The remaining Orinj Compressor controls are described below:

  • Band tabs: Use the band tabs to switch between the frequency bands of the compressor – "< 300 Hz", "300 Hz to 1500 Hz", and "> 1500 Hz".
  • Graph: Use the graph to add compressor points. The graph shows how the compressor changes the amplitude of the output signal based on the amplitude of the input signal. The horizontal axis of the graph shows the different possible levels of the input signal – from -50 dB to 0 dB. Here, 0 dB is the maximum input signal (i.e., since this is a digital processing effect, this is the maximum signal that can be recorded digitally; see Sampling resolution). Usually, -60 dB is considered silence. The vertical axis shows the ratio of compression or expansion applied to each input signal. The compression / expansion ratio is between 10:1 and 1:10. The points on the graph show where the compression ratio changes. You can click on points to select them (the selected point will be shown in white; others will be in yellow). You can drag points to move them. You can also click anywhere on the graph to create a new point. (Points are removed with the Remove and Remove All buttons explained below).
  • Threshold: Use these controls – the box and the slider – to set the threshold of the selected point in the compressor. Many simpler compressors have only one threshold. This compressor allows several threshold points and, consequently, several compression / expansion ratios between these thresholds. You could, for example, expand (make louder) the quiet parts, compress the louder parts, and leave the middle amplitude parts unchanged. As in the graph above, the threshold is measured in decibels and each threshold point can be placed anywhere between 0 dB and -50 dB.
  • Attack: Use these controls – the box and the slider – to set the attack of the compressor. The attack is the time it takes for the compressor to change the amplitude of the signal so that the compression / expansion ratio moves from 1:1 to the needed compression / expansion ratio. The attack is measured in milliseconds (ms) and can be between 0 ms and 200 ms.
  • Release: Use these controls – the box and the slider – to set the release of the compressor. The release is the time it takes the compressor to change the amplitude of the signal so that the compression / expansion ratio changes from the needed compression / expansion ratio back to 1:1. The release is measured in milliseconds (ms) and can be between 0 ms and 2000 ms.
  • Knee: Use this slider to define how smoothly the ratio of compression or expansion changes from one level to the next. At the "minimum" value, there is no knee and the transition from one compression / expansion ratio to the next is sudden. At the "maximum" level, the transition is most smooth. This slider controls the transition at all threshold points of the compressor at the same time.
  • Forward: Use these controls – the box and the slider – to set the amount of time that the compressor looks ahead when adjusting the amplitude of the signal. With value of 5 ms, for example, the compressor will begin to adjust the amplitude of the signal 5 ms before that signal reaches a compression / expansion threshold. This look ahead time parameter is included to allow quick compression at the very beginning of signal peaks, but without a very short attack, since very short attacks can change the underlying form of the signal and introduce distortion. If the attack of the compressor is also set at 5 ms, then the compression will reach its full compression / expansion ratio at the moment at which the signal reaches the specific compression / expansion threshold. The amount of time that the compressor looks ahead is measured in milliseconds and can be between 0 ms and 10 ms.
  • Peak / moving average: Use these buttons to select whether the compressor should monitor the peaks of the amplitude envelope or an average of the values of the amplitude envelope for an interval of time (see below for the length of the interval). A moving average of the values will make the transitions between amplitudes and the corresponding reactions of the compressor smoother.
  • Average: Use these controls – the box and the slider – to define the length of the interval, over which the compressor will compute and monitor a moving average of the values of the amplitude envelope. The moving average interval is measured in ms and can be between 0 ms and 100 ms.
  • Compress / expand ratio: Use this slider to change the compression / expansion ratio of the selected point in the graph. The selected point is in white (all other points are in yellow). The compression / expansion ration can be between 10:1 (compression) and 1:10 (expansion).
  • Input: Use these controls – the box and the slider – to give additional gain to the input signal of the compressor. Increasing the input gain of the compressor is equivalent to lowering the threshold of the compressor. Using the input gain may be easier, if there are several threshold in the compressor. This gain is measured in decibels and can be between -20 dB and 20 dB.
  • Output: Use these controls – the box and the slider – to give additional gain to the output signal of the compressor. This gain is measured in decibels and can be between -20 dB and 20 dB.
  • All bands: Click on this control to make all three compressor bands the same. The compressor will adjust the parameters of the second and third frequency bands, so that they are the same as the parameters of the first compressor band.
  • One band: Click on this control to create a compressor that does not use frequency bands. When the three compressor bands are used, even if they have the same parameters, the frequency content of the signal will change, as the amplitude of different frequencies will reach different compression thresholds at different times. This can be avoided, if the compressor operates without splitting the signal in three frequency bands.

See Orinj Effects for additional notes on: where Orinj effects can be used, using boxes and sliders that impact the same parameter (such as the box and slider for the compressor attack), applying effects to mono and stereo waves, and using effects during playback. See Orinj Working with effects for additional information on creating, modifying, moving, removing, and processing effects. See Compressor / expander (of dynamics) for additional information on the compressors in audio processing.

The Orinj version 2 Compressor

The Orinj version 2 Compressor dialog

The Compressor in version 2 of Orinj does not have controls for the knee. It is also not a compressor that looks ahead and there are no controls to change the look ahead time. There are also no options to use a moving average over the amplitude envelope of the signal. This compressor also cannot be treated as a single frequency band compressor.



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