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Topic: Track Loudness Normalisation, some newbie questions. (Read 659 times) previous topic - next topic
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Track Loudness Normalisation, some newbie questions.

So I have a bunch of FLAC files, and I stream them as a radio station for my own personal use, and using LiquidSoap as a playlist script and ICECast.
As these are tracks from different albums and such, I want to normalise the volume.

I have normalise added to my Liquidsoap script and it does a reasonable job, however sometimes it gets thrown by a track that starts quiet and then gets louder, you can hear that liquidsoap turns the gain down, and it's obvious the track was messed with.

Is there a way to be smarter about this?  Perhaps scan all the audio in advance and use replaygain tags?  (do these work in FLAC, does liquidsoap use them?).  I'm also a bit confused about the different ways of calculating gain, in particular were tracks are from totally different sources and may be thrown together in any random sequence by my radio script.

I suppose last point is, I run this from a synology NAS, and pre-processing files once rather than every time seems like a better, more efficient  way of doing things.

I guess this must be possible, as radio stations do this, I'm really wondering how they do it, if it's the best way for me to do it (given different hardware resources), or are there better ways of doing it.


Re: Track Loudness Normalisation, some newbie questions.

Reply #1
I don't know anything about liquidsoap or ICECast...

ReplayGain, WaveGain, and MP3Gain all work by pre-scanning the files and then one adjustment is made before the track starts playing so it's not adjusted during playback and dynamics are not affected.    All of the popular streaming services use similar techniques.

ReplayGain tags the files so your software has to support it.

WaveGain and MP3Gain make "permanent" changes to the file so they work with any software.    I don't know if there's something similar for FLAC but since FLAC is lossless you could convert it to WAV, apply WaveGain, and then make a new FLAC.

I guess this must be possible, as radio stations do this,
Broadcast stations use dynamic compression and limiting to keep the program "constantly loud".

Re: Track Loudness Normalisation, some newbie questions.

Reply #2
For use on phones, etc, I use foobar2000 to convert from FLAC to a lossy format and apply whichever gain (I use Album) within the conversion. That's 363GB of FLACs converted in one hit.