Some movies have portions that are really quiet and others that are quiet loud. Depending on your taste you may prefer to not have the experience of turning up the audio so you can hear a quiet conversation, then having your ears blown out by a loud explosion or whatever. Director's tastes be damned, I'm trying to relax over here!

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jack1243star 5 days ago | parent [-]

In audio processing, the more precise term for it is compression (dynamically adjust gain). Normalization usually means that the gain is adjusted so that the highest volume meets a certain level. (Like what YouTube does)

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lucideer 5 days ago | parent | next [-]

Compression is an entirely different thing.

Compression isn't just gain adjustment - it's a specific type of audio processing that increases perceived "gain" (loudness) of the entire source audio by "compressing" the levels of loud frequencies & increasing the levels of quiet frequencies.

Normalization increases gain of all frequencies at any given point-in-time while reducing gain of all frequencies at other points in time. It doesn't reduce dynamic range.

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danadam 5 days ago | parent | next [-]

> Normalization increases gain of all frequencies at any given point-in-time while reducing gain of all frequencies at other points in time.

When you do that then the difference between the loudest and the quietest part of the audio gets reduced. That's dynamic range reduction.

	▲	lucideer 5 days ago \| parent [-]
		True. But. While normalization is usually one-way, if you're doing DSP normalization & have a record of the level offsets you've applied, it's reversible. This is never the case for compression - you can't increase dynamic range of a compressed file (short of AI-generating something that never was)

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recursive 5 days ago | parent | prev | next [-]

I think you're describing a multi-band compressor. "Normal" compressors do indeed do gain adjustment. They usually do this without regard for the frequencies present. Only the amplitude matters for normal compressors.

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lucideer 5 days ago | parent [-]

Not specifically talking about multiband.

Normal compressors do effectively do gain adjustment - it's not really the same as a typical amp since their core function only reduces gain, then makeup is applied to the entirety to compensate - but yes the result is effectively gain adjustment.

As for doing it "without regard for the frequencies present", if you compress a mix with a base guitar & high vocals, the impact of the compression on the base will be different than on the higher notes. This is aside from (/in addition to?) attack & release applied on a per-track basis & more just about the natural effect of dynamics within frequency ranges.

	▲	recursive 5 days ago \| parent [-]
		Are you referring to psychoacoustic effects? Something like perceived loudness is only determined by waveform amplitude, but also affected by frequencies present? Or maybe the vocal and bass parts have transients at different times causing the other to be attenuated when it was already relatively quiet? Other than that I'm not sure what else you could mean. Maybe we've been using different compressors. I've used a small handful of hardware and software compressors and haven't found them to sensitive to spectral content when used "normally". Meaning no extra filters or side chain configuration.

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throwaway290 5 days ago | parent | prev [-]

Sorry but you really misunderstand what normalization and compression means. "quiet frequencies" :D

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lucideer 5 days ago | parent [-]

I assure you I don't.

I'm not sure what the scare quotes are about but if you point out what I'm misrepresenting I can try to explain it a little better.

	▲	throwaway290 5 days ago \| parent [-]
		You don't need to explain, I know the subject. Compression acts on the amplitude of the entire audio signal, not "quiet frequencies". You can start here: https://en.wikipedia.org/wiki/Dynamic_range_compression Normalization as it normally is used is offline process where you up the gain of the whole audio so that the loudest noise is 0dB.

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thayne 5 days ago | parent | prev [-]

But compression is ambiguous because that could also refer to compressing the video stream to reduce the size of the movie.

	▲	kbouck 5 days ago \| parent [-]
		> compression is ambiguous I think the unambiguous term for this is "Dynamic Range Compression" https://en.wikipedia.org/wiki/Dynamic_range_compression