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Topic: How to apply replaygain without clipping? (Read 340 times) previous topic - next topic
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How to apply replaygain without clipping?

Hello,

I'm trying to extract tracks from a DVD audio iso. It turns out the final flac will have clipping even if I turn on the clipping prevention in replaygain settings. The only way to actually prevent the clipping is to use -6dB hard limiter or manually decrease the volume on preamp setting. However, I wish to apply replaygain peak information to get the best result. How can I use it to get the best gain without clipping? Here is my procedure to show the problem.

Poting

PS. the clipping exists even if I turn off replaygain.

1. Select the tracks and perform replaygain peak scan.




2. Replaygain scan result




3. In converter menu, enable replaygain and choose clipping prevention.




4. Output settings




5. In Audacity, it hows many clipping in the whole file.




6. Magnified view on one of the clipping.



Re: How to apply replaygain without clipping?

Reply #1
You do everything correctly. The peaks in the source are already at digital fullscale in several tracks so in this case you will get bit-for-bit identical FLAC version. Lowering the amplitude won't remove the clipping but it can hide it from Audacity. The -6dB hard limiter DSP will start limiting the signal 6 dB below the fullscale. It will prevent samples from hitting the highest value but it will also alter the frequency response. The change is very likely inaudible in this case, but it can't fix clipping that is present in the source either. It can be useful to prevent boosted signal from distorting too much.

 

Re: How to apply replaygain without clipping?

Reply #2
If you find the clipping audible and objectionable, you can attempt to fix it with commercial VST effects made for this purpose: Stereo Tool and Izotope RX. They work quite well on short clipped sections heard as crackle, and don't really add side-effects until the clipping is so severe that there are dropouts. Correctly configured, the plugins will pass through quiet audio unmodified, and only affect samples above (and around for ST) the threshold.

Re: How to apply replaygain without clipping?

Reply #3
The peaks in the source are already at digital fullscale in several tracks so in this case you will get bit-for-bit identical FLAC version.

I suspect that is the case. I presumed the source "should be" perfect, free from clipping, but I could be wrong.

Poting

Re: How to apply replaygain without clipping?

Reply #4
If you find the clipping audible and objectionable, you can attempt to fix it with commercial VST effects made for this purpose

Thanks for the tip. No they are not audible, so I can live with that. I even suspect they did this in purpose, because the dynamic range is very high in this recording. Perhaps they sacrificed some peaks to make the music more audible. Well, this is just my wild guess.

Poting

Re: How to apply replaygain without clipping?

Reply #5
Some audio editors interpret even integer peak maximum as clipping, even if it doesn't have the shape of a clipped peak.

Re: How to apply replaygain without clipping?

Reply #6
I even suspect they did this in purpose, because the dynamic range is very high in this recording. Perhaps they sacrificed some peaks to make the music more audible.
Yes, I agree with the assessment. The average level is already low, and you'd have to decrease it further by 3-4 dB to accomodate the peaks. Declipping also adds bass, which may turn out to be too loud to play back on speakers, without compression or soft-clipping (usually my choice).

Re: How to apply replaygain without clipping?

Reply #7
Just another example from Alanis Morissette's Under Rug Swept DVD Audio disc. It contains even more clippings (a lot!). Now, I believe they are from the source.



Re: How to apply replaygain without clipping?

Reply #9
Whether some samples are highlighted in red doesn't change how they sound (the ISP debate aside). It is very common for clipped peaks to be at -0.3 dB or at a similar level, where they will not light up indicators in most software, and probably why the level is reduced in the first place. To identify clipping you first hear it, then identify it on the waveform by zooming in. If the tops are flat, then the clips can still be fixed. If the clipping is "baked in" by further equalization or recording to tape, then almost nothing can be done. The style of music influences whether clipping is a problem. If only a few successive samples are at zero, I won't hear that in rock music, but might in an acoustic or vocal passage.

 
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