Get same output levels on a large batch of mp3's

Audacity Help Forum Windows
1

Hi
I’m am new to this forum and audacity, so please excuse my ignorance.
I want to put all my mp3’s into audacity, and make sure they all have the same output volumes whilst playing, of which I will copy onto a SD card for my car.
I want to do a large batch or all of them together rather than one at a time, I also want to change the hertz rate so they are all the same, probably 48000hertz

Can anyone help please?

Thanks Gary

2

Do you mean the same peak volume, or the same apparent loudness? The first is not a good indicator of the second.

Is there a reason you need to do that? That will mean you MUST re-encode the MP3’s and lose quality, whereas we’re going to suggest that because Audacity always re-encodes MP3, you can use other tools to perform only volume adjustments without quality loss. See: http://wiki.audacityteam.org/wiki/Lame_Installation#lossy .



Gale

3

Notes:

I would use the sound standard of 44100, 16-bit, Stereo, WAV. That’s what’s on a Music CD. 48000 is the video standard and certainly in this case overkill for no benefit. You can change that default in Audacity. Audacity > Edit > Preferences > Quality.

You may benefit from Chris’s Compressor.

http://theaudacitytopodcast.com/chriss-dynamic-compressor-plugin-for-audacity/

Chris (no longer with us) designed this volume manager so he could listen to opera in the car. It gracefully evens out loud/soft volume variations between and during songs. I use it to listen to talk shows in Lori (my lorry).

I have only ever found need to change the first option number, Compression, from the default of 0.5 to a stiffer 0.77.

Here is a sample of what happens to a song’s blue waves for each setting. None, 0.5 and 0.77.

http://kozco.com/tech/audacity/pix/ChrisCompressorBeforeandTwoAfters.png

You can set up a Chain (Audacity for “batch”). Open each file, Apply Chris, Export as WAV, Next.

Now you know as much as I do. I have never used Chains.

http://manual.audacityteam.org/o/man/chains_for_batch_processing_and_effects_automation.html

Koz

4

As above, trying to manage MP3 is messy. Audacity always makes new ones and in the process creates distortion. Other tools may not batch properly. Since you’re on an SD card, there is effectively no top end of storage, so you can use the much higher quality WAV format. The sound won’t get any better, but it won’t get any worse, either.

You also happened to have the job that these tools were designed for.
Koz

5

In case this is confusing, I am talking about each MP3 having the same peak (or apparent) volume as the next one in the playlist.

Koz is talking about making each MP3 have a similar volume throughout its length, so you don’t have to reach to turn the volume up in the quiet bits. If you compress to the same peak volume in Chris’s Compressor, it may “sort of” make each MP3 sound as loud as the next. But not in classical music.

If you want compression, you’ll have to re-encode and lose quality.


Gale

6

MP3DirectCut and MP3Splt both have batch processing ability to change volume levels losslessly.


Gale

7

[u]MP3Gain[/u] will automatically adjust your MP3s to a standard loudness.

Note that most commercial releases (including most quiet-sounding tracks) are normalized/maximized (with 0dB peaks) so you can’t boost the volume linearly without potentially clipping (distortion). This means that means that MP3Gain will tend to make your loud tracks quieter, rather than boosting the quiet-sounding tracks. Some users complain that their music is too quiet after applying MP3Gain.

Compression is non-linear and it CAN boost the average level without boosting/clipping the peaks. But, compression changes the “character” of the sound.

8

Hi Gale.
Thankyou and everyone else with your responses. I want to make each song the same volume. For some reason I have one or two songs within my library that are either louder or quieter than some others, and can make you jump when a new song comes on and is much louder than the others.! So basically I want to batch the whole lot at once and make them all the same output sound level.

Thanks. Gary

9

Older songs and performances conform to the original Music CD specification which had the US VU value of -17dBu. Someone found that they could sell more records if they simply smashed music on the disk as loud as they could get it – the heck with music standards.

My older Patsy Kline recordings vanish when played next to the later music such as BR549.

“Welcome to the hill-billy beat sound. We’re glad you’re here!!”

You’re so glad, the track actually has data overload points in it…

We recently messed with a poster’s rhythm track loop that was almost 100% overload. Patsy doesn’t stand a chance.

Koz

10

OK so if you forget about wanting to make them all 48000 Hz - which will inevitably degrade their quality due to the re-encoding - and assuming you are talking about perceived loudness, you’ll probably want to use MP3Gain.

MP3Gain is lossless, and is an implementation of a ReplayGain algorithm that calculates perceived loudness. The volume information is written inside the “metadata tags” in the file.

MP3Gain can run on a group of files all at once. I assume your player doesn’t read ReplayGain tags. If so, you will have to choose the button to apply “Track Gain” . This will actually make the MP3 quieter or louder even if the player does not read ReplayGain tags. It does this by modifying the “scale factor” in each MP3 frame.

Don’t choose “Album Gain” as this will treat each file folder as an “album”. It will retain individual differences between each song in the album and only make the levels of the albums equally loud (like changing the volume knob only once for each album).

If you don’t like the result on any files, MP3Gain can undo the gain change.


Gale