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Help with MP3 Gain?, Lots of red
cryssy324
post Oct 11 2012, 10:47
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I'm new with MP3 Gain and I'm doing a track analysis right now with my music at 91.0 dB. This one causes the least red Ys under the clipping(Track) column. But most of my mp3s have red Ys under the 'clipping' column. How do I fix this? For some of the mp3s, they have a red Y under the clipping column no matter what dB i set it to.
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Dynamic
post Oct 11 2012, 19:09
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When you've analyzed but not applied any gain, this is the status:

The Clipping column means that the MP3 is already clipping on decode at its current volume (the current loudness is shown in the left column of numbers). This can happen if the CD came close to full scale (like most modern CDs that frequently have ReplayGain loudness of 95 to 99 dB) and the MP3 might reach 1.1 or 1.2 times full scale at its peak because MP3 doesn't try to accurately preserve the waveform peaks, just the sound. Changing the target volume will not change this column.

If you actually apply any gain to the MP3, you now have a different MP3, and MP3gain will automatically adjust the current loudness and the Clipping level (it has stored the track peak at the original loudness and via a quick calculation, knows the peak level at the new loudness).

To the right there's also a set of columns regarding the amount of gain to be applied if you Apply Track Gain, and whether it would then clip, and on the right side, are columns about the amount of gain it will apply if you Apply Album Gain and whether it would then clip.

It's quite probable that clipping of up to 1.2x peak (corresponding to the 1.5 dB step size) will be over only 2 or 3 samples duration and during transients, and very likely inaudible, so you might get away with increasing the target volume to 1.5 dB above the Max No Clip Gain, albeit at some risk of generating high frequency clipping distortion components that could fry or fuse a tweeter.

It's likely that all the CDs you're looking at were mastered in the last 10 years (even if the original release was earlier) and are all victims of the Loudness War and can be expected to clip at 1.1 to 1.2 times full scale when encoded to MP3. (otherwise people complain that the CD is too quiet)

For normal use on a PC, perhaps through an amp or home theater setup, 89 dB target is pretty good. If you listen to a lot of classical or want to match levels with movies, 83 dB might be better. Both provide plenty of headroom for peaks in most music.

However, many portable players and phones have European peak-level limits mandated (sometimes you can beyond if you set it up as if outside the EU), which means that loudness-war era tracks (most tracks since 2000) will not be too likely to damage hearing despite having average loudness almost at the peak level.

However, if you really want to achieve higher loudness for restricted/crippled hardware and if you encode the MP3s from lossless yourself, you might be better using a Dynamic Range Compressor DSP with Peak Limiter before the MP3 encoder (and foobar2000 can help) and live with some reduction in dynamic range and punch in exchange for loudness. Ideally, you'd get a player app with a dynamic range compressor (DRC) as a built in option (e.g. VLC media player on a PC goes to 200% volume by progressively introducing DRC, I believe. I haven't been able to test the Android version on my low-end phone)
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DVDdoug
post Oct 11 2012, 19:49
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QUOTE
I'm new with MP3 Gain and I'm doing a track analysis right now with my music at 91.0 dB.
At 91dB, you are not giving MP3Gain much "room to work" without addtional clipping.

Peak levels don't correlate well with loudness, so you can have clipped files that don't sound loud. Obviously, you can't boost those files without more clipping. If you want to match the volumes of all your files (without clipping) some (most?) of your files will have to be made quieter.

f you don't care about clipping, you can use any dB setting you like and MP3Gain will match the volumes. But, if you want to prevent clipping you will have to use a lower setting and allow MP3Gain to reduce the volume on many (most?) of your files in order to make the volume (nearly) equal on all files.

If you use 91dB and configure MP3Gain to prevent clipping, MP3 gain will "do nothing" with much of your music. Any "quiet" songs that are currently clipping (or that are near clipping) won't be changed. However, louder-sounding songs (clipping or not) will be reduced as-usual to match your 91dB setting.

A higher target dB setting means there is more chance of needing to boost volume to hit your target volume. And as you boost volume, there is a greater chance of clipping. There is no perfect setting... 89dB is the default compromise that works with most files, and it will probably make most of your songs quieter.

P.S
I'm not saying you shouldn't use 91dB. I just want you to understand what MP3Gain is doing, and that there is a potential downside to going louder.

If you just want to make all of your files as loud as possible without clipping (and without any volume matching) you can normalize the files, which will set the peaks to 0dB. Of course, many (most) of your files are already normalized, so re-normalizing will do nothing. (The files may still show some slight clipping after MP3 encoding.)

Or as Dynamic suggested, you can use dynamic compression to boost the average level without boosting/clipping the waveform peaks. But, this reduces dynamic contrast and the constantly-loud music can get very boring!

This post has been edited by DVDdoug: Oct 11 2012, 20:10
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