Limiter doesn't limit

[blaubär]

I tried to find out what exactly the limiter does and how it affects distortion. On my Samsung S7 with Oreo and build 823 ( high-res, sampling rate 44.1 kHz, wired headphones ) I chose a song ( mp3, 44.1 kHz ) with a significant amount of bass.Then I activated Tone and EQ and set the bass in both to maximum level, including the eq-preamp. I expected to hear distortions, which would then be diminished after I would have activated the limiter. I would try that both for DVC and non-DVC and didn't expect a difference there.

Result : without DVC I heard distorted sound, limiter or no limiter didn't make a difference. With DVC I didn't hear distortions, again the limiter didn't make a difference.

Question : Bug or Feature ?

I'd say bug : the limiter should have prevented the distortions.

That there were no distortions with DVC might be a feature of DVC - but then I'd expect the limiter button to be inactive.

[andrewilley]

I would assume that with DVC on, Poweramp has more processing headroom than it does with DVC off.

Andre

[blaubär]

26 minutes ago, andrewilley said:

I would assume that with DVC on, Poweramp has more processing headroom than it does with DVC off.

If that were the case one would expect the music to become louder when DVC is switched OFF. 

But it's the other way round : the music gets louder when I switch DVC ON.

I found a theory as to what DVC does in https://www.head-fi.org/threads/best-android-music-player-app.638387/page-2

That's the Direct Volume Control feature kicking in.  It adjusts the system volume such that if you do boosts in the graphic EQ, what it does instead is boost the system volume then apply EQ cut to everything except the boosted band. 

That might explain both the vanishing distortions and the higher volume level with DVC on.

Edited April 1, 2019 by blaubär
additional info

[blaubär]

So with DVC the limiter doesn't need to limit. But without DVC it should limit, but it doesn't. So that's a bug ?

[blaubär]

Shouldn't the limiter mitigate all the bass distortions that users complain about ?

If it doesn't, what's it for ?

[blaubär]

I could think of two ways a limiter could work :

- compress the dynamics, as shown in the wikipedia : 

- preventively reduce the pre-amplification by the amount of the highest eq increase minus headroom

But it seems it does neither.

@maxmp : what does the Limiter do ?

[Alexmercer910]

Hi there, i seem to be having the same issue with my Poweramp but only after unofficially updating to android 11, it seems like the bug only exists on the new OS that i installed, so maybe its a device specific issue, but still im trying to figure it out, maybe it has something to do with the audio codecs installed with the ROM or something, im not sure yet.

[andrewilley]

@Alexmercer910 What exact issue are you getting?

Andre

[Mths]

I'm also trying to know how exactly the limiter will affect my sound output. Per example, what settings is the app limiter operating on?

[andrewilley]

Basically if the processed sound would peak over the digital maximum level (100%) then PA will reduce the gain to avoid clipping.

Andre