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Kalle Rantaaho

Mp3-conversion - level change?

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Please refresh my memory.

I remember reading here (or in the old forum) several times, that you should not export/master to 0 dB level if you're going to later convert the file to mp3, but rather export to -0,3 dB max. This being due to slight level raise in the conversion, and possible digital distortion/clipping in the mp3-file.

I expressed this view on another forum and I've been "challenged" to give some background to what I wrote.

Is my memory failing? 

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Sorry I don't know the exact answer but I myself use the same -0.4 for masters which is were I set either the BT Brickwall or the free Loudness Max listed below.   . I then convert them to 190 bpm MP3 in goldwave.   If I load them into Wave lab they are almost identical as far as levels and RMS go. 

What I'm using now is a few different plug ins that you can put on your master buss that have all these different standards as presets. 

These are free- 

https://www.voxengo.com/product/span/

https://youlean.co/youlean-loudness-meter/

https://www.kvraudio.com/product/loudmax-by-thomas-mundt

I also tried the Mastering meter by IKmedia but the trial ran out and to purchase was way to much for what it does. 

Youlean has presets so it will tell you if you have exceeded the standard but I'm not dead sure they are accurate at this point. If put after the BT Brickwall the youlean shows overs randomly. When loaded into wave lab the file always shows exactly what I set the BT Brickwalls limit to.  The Loudmax gives varying results with Youlean and in Wavelab it's not showing exactly what it was set for. So I put my money on the BT Brickwall if you were lucky enough to score it back with Splat. 

 

Edited by John Vere

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HI:)

I do not use MP3s, but I sometimes got some to edit them for some performances... (stupid not to use waves then:( )

But the'yre always totally overloaded and/or overcompressed. I'm pretty sure the conversion gives 3-4 dB of more level.

All frequencies above 15 kHz are totally cut off, what can be seen in an Analyser. 

Maybe this level raising is only affected if the Bitrate is too low, so better you use 320 kBit instead of 128!

Much better it will be to use the Wave File!

 

Before Conversion I would Master/Mix it down to -5 dB and then convert them to at least 240 kBit.

 

Bassman.

 

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the old forum is still searchable using Google

here is a similar thread on this forum

 

 

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6 hours ago, Kalle Rantaaho said:

I expressed this view on another forum and I've been "challenged" to give some background to what I wrote.

Is my memory failing? 

Your memory is fine! Spotify.com says :

Target the loudness level of your master at -14 dB integrated LUFS and keep it below -1 dB TP (True Peak) max. This is best for the lossy formats we use (Ogg/Vorbis and AAC) and will ensure no extra distortion is introduced in the transcoding process.

If your master is louder than -14 dB integrated LUFS, make sure it stays below -2 dB TP (True Peak) max to avoid extra distortion. This is because louder tracks are more susceptible to extra distortion in the transcoding process.

So if a company whose livelihood depends on streaming says that you need to reduce true peaks to avoid distortion, they've probably done their homework. Although they only specify Ogg/Vorbis and AAC, the same issue also applies to MP3. 

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In the pro version of the Youlean meter ( and others too) there is a preset for the different formats including Spotify. This to me is a lazy mans way of proofing your mixes for different outputs. Just keep adjusting your limiter of choice until your right on. 

2020-11-28.png

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If a streaming service accepts a lossless format such as FLAC, and is going to transcode whatever you upload anyway, you might as well send them the highest resolution file that they will accept, rather than MP3 (lossy).

Imagine that the rules for peaks might vary with different file formats, so running a few test uploads/transcodes with the chosen service is probably a good idea to judge the end results.

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In theory, MP3 encoding (or, more specifically the steep low-pass filters it employs) can cause peaks to increase by up to +3dB. 

Therefore, you'd have to limit to -3 dB true peak to be perfectly safe. Even then, streaming platforms may still raise the overall level if your average RMS is below their recommendation. So if YouTube says -14 dB and yours comes in at -20 dB, they'll raise it up by 6 dB or thereabouts - including your carefully limited peaks, which will then have to be limited again by their algorithm. The end result may not be what you'd have preferred.

That said, I limit to -1 dB. It doesn't guarantee absolute protection from overs, but it's conservative enough that any clipping will be probably short enough in duration to slip by unnoticed.

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The old 0.3 safe rule was for CD, not streaming, many cd pro masters are at 0.1. Mp3's were always about -1.db peaks to allow for conversion & overs.

Try this tool & try any type file;  flac, 16b or mp3,  you should see very close results. Of course the better quality used before conversion  the better.

https://www.loudnesspenalty.com/

 

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That's an interesting tool. What it's showing me is I'm generally 1.2 db too loud.

  Youlean has a similar drag and drop analyzer on the web site and if you purchase the unlocked version, which I did today because Black Friday special, it does this with more detail.  Just drag a audio file into the GUI and it spews out the Loudness and peak details for your file.  Very handy tool well worth the $39 Can.  Interesting story behind it's development too.   

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