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Auto Gain and Limiter





Auto-gain

These are the recommended and default settings to keep VirtualDJ at:

- autoGain: auto
- gainSliderIncludesAutogain: yes

For each song, VirtualDJ analyzes the loudness of the track. This is done either when explicitly asking virtualdj to scan the track, or the first time an unanalyzed track is loaded.
With autoGain set to auto, virtualdj will then lower or increase the gain of the track so that all the tracks you play have a similar volume when played, regardless of how loud it was recorded.
With gainSliderIncludesAutogain set to yes the autogain is properly applied when the gain slider is at the 12-o-clock position.
This makes it easy to control the gain with a controller, since it's easy to set it to center position for each track.
It is still possible to use the gain knob to make adjustments to the gain when required (for example boosting a quiet passage in the song or temporarily lowering the volume if it's too loud)
Note that the gain should not be used higher than the 12'o'clock position structurally. This will only cause the limiter to kick in, rather than actually boosting the volume.
If you need a structurally higher volume, increase the master volume, or the gain on your amplifier or speakers.
If they are already at their max, invest in more powerful speakers and/or amplifiers as needed.


Incorrect detection

Although the algorithm used by VirtualDJ is fine for most music, it is possible that it detects the loudness incorrectly for some songs.
This can be the case with classical music, which can have a high dynamic range with very short peaks of higher volume and many parts that are supposed to be more silent.
The easiest way to fix those is by opening the Tag Editor for these tracks, and manually reset the gain to 0 dB, which means vdj will play these files at their original gain.
It is also possible to make small adjustments by increasing or decreasing this value if necessary.

autoGain: auto+remember

This was the default in virtualdj 7. In this case the explanation above still applies, but if you move the gain slider for a song, it is remembered and automatically applied the next time.
We found that many people used this feature incorrectly however, which led to gain being set too loud and as a result causing distortion in the sound. It is therefore not recommended to use this setting.

mp3Gain/aacGain/replayGain

mp3gain is a program based on the replayGain algorithm to even out the volume differences between tracks, and is therefore an alternative to autoGain in virtualdj.
If you decide to use this, remember to re-analyze the tracks in virtualdj after, since the gain value that VirtualDJ analyzed previously would be incorrect after the file had been changed by mp3Gain.
Since VirtualDJ already has an auto-gain algorithm, it is not required and doesn't have a useful effect to use mp3Gain as well.
One disadvantage of mp3Gain is that the gain that it applies could cause some peaks in the track to clip and thus distort these peaks in order to bring the average loudness up to a normal level.
In VirtualDJ however, the gain calculated is applied at an early stage, and thus additional headroom, a lower channel volume, a lower master volume or the limiter would prevent this distortion from occuring.
One advantage of mp3Gain is that it alters the file itself, so the gain will also be applied in any other programs you use to play back these files.
If you prefer mp3Gain, it might make sense to set autoGain in VirtualDJ to no, although in that case you have to remember to use mp3Gain on all new files as well.
Regardless, you should re-analyze all files in VirtualDJ after you apply mp3Gain on them.


Limiter

VirtualDJ has a built-in limiter to protect the audio output from distorting. It is important to remember that it is *only* active if the sound would be too loud otherwise and cause clipping distortion.
As long as the output stays within the digital limits, the limiter does not affect the audio in any way.
It is normal and usually not a problem if the limiter kicks in lightly and temporarily during a mix of two tracks, or at some peaks of the track, but if it is working constantly you will notice how it affects the sound negatively. (Although it is still less noticeable compared to the clipping distortion that would have happened without the limiter). You can try how this sounds by turning up the gain or equalizer all the way.



headRoom/zeroDb

By default, the gain structure in VirtualDJ is set up in such a way that playing a single track at full volume with gain and equalizer in the center position will sound similar to playing audio in other applications.
In this case the full digital scale will on average be used.
The advantage is that when playing like this, the dynamic range of your output stays constant, and it controlling the volume of the audience is done at the amplifier level or by the sound engineer.
The disadvantage is that there is no headroom left for temporary boosts in volume.
For this purpose, it is possible to use the zeroDb option in VirtualDJ. You can set it to -3dB or -6dB for example to create additional headRoom.
The output of a track at full volume with gain and eq at center position will now be 3 or 6 dB lower (you can increase the volume of your speakers/amplifier to adjust for this). Which means you now have some headroom left to temporarily boost the volume using the gain or eq sliders, or when mixing 2 songs together without the limiter kicking in.
As is the case with the gain control in general, keep in mind that it is again not useful to constantly play with the gain control increased. If you structurally need more loudness, do it at the amplifier/speaker level instead.



Mixing and loudness

With many types of mixing, you will often have two songs playing at the same time.
When two songs are playing at the same time at full volume, you should realize that the output can potentially be twice as loud as well, which your audience may not appreciate. With no headroom configured, this will typically cause the limiter to kick in, automatically lowering the volume, but it may also cause some pumping sound that may be undesirable.
Another problem is that when bass sounds are not perfectly aligned, they may cancel each other out, which is also undesirable (or worse, since the bass frequencies of both songs are not perfectly the same, the phase will slowly shift, causing the bass to shift from canceling out to being twice as loud)
To eliminate all these problems, it is useful to learn how to use the equalizer to move from one song to the other. Typically you would kill the bass on the song you are mixing in, and then bring it in, while at the same time moving out the bass of the track you are mixing out.
This ensures the output volume remains more constant and prevents possible distortion.




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