Tech: MP3 Properties

Subject: Tech: MP3 Properties
From: Brakn
Date: 03 Jun 08 - 10:36 AM

I have recorded some audio tracks as MP3 files and I now think that I have recorded them at the wrong volume - too quiet. If I now alter the volume of the MP3 files in a sound editor will that affect the quality or should I just rerecord from audio(which would be a bit of a pain).

Any views on this.

Michael Bracken

Subject: RE: Tech: MP3 Properties
From: nickp
Date: 03 Jun 08 - 10:55 AM

Boosting the volume in a sound editor shouldn't make an audible difference to the quality.

Subject: RE: Tech: MP3 Properties
From: Mitch the Bass
Date: 03 Jun 08 - 11:13 AM

If your audio editor decodes the mp3 so that you can then change the level and then re-encodes it you may encounter some quality degradation as mp3 encoding is not lossless.

There are some editors which can do this without decoding. Take a look at mp4 trimmer http://deepniner.net/mp3trimmer/

Mitch

Subject: RE: Tech: MP3 Properties
From: Bernard
Date: 03 Jun 08 - 01:52 PM

Try here (MP3 Gain).

This is a normaliser that works directly on the attributes within the file instead of editing the audio. You can use it to make all your MP3 files sound as if they are at the same level (which is what normalisation means).

Subject: RE: Tech: MP3 Properties
From: Brakn
Date: 03 Jun 08 - 02:12 PM

Thanks so far. I would probably use Cubase; load the MP3 file, alter the volume and then save again. I don't know if that decodes or re-encodes the file.

Subject: RE: Tech: MP3 Properties
From: Brakn
Date: 04 Jun 08 - 08:30 AM

frsh

Subject: RE: Tech: MP3 Properties
From: Darowyn
Date: 05 Jun 08 - 04:06 AM

The ideal way would be to go back to the original Audio, normalise that and then re-code it as MP3.
The problem is that digital audio records volume levels as numbers. The more numbers you use, the closer the number is to the analogue volume level. So if,to keep things very simple, you recorded with two bits, that would give you a number 0 for silence and a number 3 for very loud (00=Zero,01=One, 10= two, 11=Three).
If the levels were low, and the loudest part of your music came out as a 01(one), then the digital recording could only show whether there was no sound, or some sound. A sound that was in between would have been recorded at a wrong level.
Recording digitally at a too low level, while it's not as extreme as that, creates quantising errors which you hear as noise on the track.
If you then boost the volume of the erroneous track, you will boost the noise as well.
In professional recording, the process of keeping the signal at the ideal level throughout is called gain staging- and is the first step towards recording quality.
It's a very technical subject, and there are those who don't care about audio quality- but I find that a poor recording just misses an important part of the sensual pleasure of music.
Cheers
Dave

Subject: RE: Tech: MP3 Properties
From: treewind
Date: 05 Jun 08 - 09:48 AM

Best way is to start again - re-record at higher level, then encode to MP3.

Next best way is a special MP3 editor that adjusts the scaling without decoding and re-encoding. That won't impact the sound quality at all, but the volume adjustment steps are quite coarse - might be 6dB. Easy and good.

Next best if you recorded to .WAV bfore MP3 encoding, is to adjust the .WAV file in any sound editor and re-do the MP3 encoding.

Laziest and worst way is to load into Cubase, Audacity or other sound editor, adjust and save, because when you save you've been through the lossy encoding process twice and lost more sound quality. If your original MP3 bit rate is 128kbits/s, I wouldn't recommend this - it will sound pretty rough to almost anyone. At 192k or more you might get away with it.

Anahata

Subject: RE: Tech: MP3 Properties
From: GUEST,Ravenheart
Date: 05 Jun 08 - 02:04 PM

Here is a cheap but useful MP3 editor for Windows. I haven't used it extensively yet, but it seems to perform well.