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Hydrogenaudio Forums > Lossy Audio Compression > MP3 > MP3 - General

Squibbles1092

Jun 27 2004, 19:33

I've adjusted all my songs to 89 db but the volume is way too low when played on my iPod. I have to keep it adjusted to about 75 - 80% Max volume. This is too high, and causes me to worry about my battery life. I'd like to keep it at 50% and still achieve a good volume. So I've decided to mp3gain it to 93 db. But will adjusting it multiples times using Mp3Gain degrade sound quality? .. Can of like encoding an Mp3 multiples times...

THanks.

Madrigal

Jun 27 2004, 20:18

QUOTE (Squibbles1092 @ Jun 27 2004, 01:33 PM)

...will adjusting it multiples times using Mp3Gain degrade sound quality?

No.

Regards,
Madrigal

be020261

Jun 27 2004, 21:54

Here's why:

Quoted from help file of MP3gainGUI:

QUOTE

The other good news is that this volume adjustment is completely lossless. In other words, if you adjust an mp3 by -6 dB and then change your mind, you can adjust it again by +6 dB and it will be exactly the same as it was before you made the first adjustment.

Here's the technical reason why it's lossless, and also why the smallest change possible is 1.5 dB:

The mp3 format stores the sound information in small chunks called "frames". Each frame represents a fraction of a second of sound. In each frame there is a "global gain" field. This field is an 8-bit integer (so its value can be a whole number from 0 to 255).

When an mp3 player decodes the sound in the frame, it uses the global gain field to multiply the decoded sound samples by 2(gain / 4).

So if you add 1 to this gain field in all the frames in the mp3, you effectively multiply the amplitude of the whole file by 2(1/4) = 119% = +1.5 dB.

Likewise, if you subtract 1 from the global gain, you multiply the amplitude by 2(-1/4) = 84% = -1.5 dB.

Architectonical

Jun 29 2004, 11:47

Correct me if I'm wrong, but in regards to battery life, there is no need to re-mp3gain your files. The battery life would depend on the actual volume, not the number on the unit. If you will still be playing the mp3s at the same actual volume level, then the battery life should be the same regardless of what volume number it says on the iPod.

NeoRenegade

Jun 29 2004, 14:01

That is absolutely right, architectonical.

The reason why playing songs at high volume drains batteries a bit faster is because more power is being supplied to your headphones, not because of anything to do with the recorded volume level of the file.

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