DC offset tool (plug-in)

In http://forum.audacityteam.org/download/file.php?id=6436 there is a typo in the action line
“Asjusting DC offset…”


I noticed the following behaviour which I don’t understand.

1 Generate White Noise at amplitude 0.0005.
2 Effect > DC offset.
3 Add offset or Remove then Add, Dynamic, +0.84.
4 Effect > DC offset.
5 Remove offset, Dynamic.
6 Effect > Amplify offers + 30.6 dB to maximise amplitude which looks “wrong”, but click OK.
7 The actual amplitude is now about -34 dB but Effect > Amplify does not let you amplify further without enabling clipping. Normalizing to 0 dB similarly does nothing.

If instead at step 4 I remove the offset using Effect > Normalize then I can maximise the noise to 0 dB as expected using Amplify or Normalize.


Similarly, if you use: Effect > DC offset: Remove offset / Absolute

In step 3 you added an “absolute offset” of +0.84, so the best way to remove that is with the “Absolute” method (which is also the method used in Normalize).

In step 1, if you generate 10 seconds of the noise, then after step 5 (Remove offset, Dynamic) look at 9.90 seconds and you will notice a slight “ripple”.
We had a huge DC offset (step 3) which “Dynamic” offset correction was not able to fully correct and a small (about -30 dB) ripple remains at the end. When amplified in step 6 this ripple is amplified to 0 dB.

OK, I was using a minute of noise. I might have possibly seen the “wiggle” (and the spike after “removal”) if it had been 10 s of noise.

I notice the same “problem” exists even if the added offset is as low as +0.15.

I deliberately didn’t do more than skim read the first post here (which didn’t help), and with no help in the plug-in and dynamic as default, perhaps this is something you need to address in the documentation when you release it?


or fix it?

Ideally what I would like is a “one size fits all” method of DC offset correction, but achieving that is not easy, particularly if it is to work reasonably quickly in Nyquist,

Indeed, fixing it would be even better :smiley:

I thought it was already fixed from what I had read here. :wink:


Not “fixed”, just “greatly improved” (provided that you use the right tool for the job) :wink:

I found this plugin very useful, not just as a visual demonstration of DC offset.

In the video game Counter Strike:Global Offensive, there is a way to play music in game via the voice chat system for others to hear. The application that makes this possible is called Half Life DJ.

The voice chat system uses an AGC to normalize conversations, but it results in music that is too loud. By reducing the overall gain and adding a DC offset, the AGC is fooled into thinking the signal is louder than it actually is, and the result is that the music plays at a lower volume than before.

:smiley: clever.

can you fix this link ? it’s private files :smiling_face_with_tear:

Lots of links got broken when the new owners migrated the forum to new software.
The link should be working now.

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