Encoding MP3s - Quality vs File Size

We often want our MP3s to sound as close to the original quality of our song as possible, so people can get a true impression of what we've created.

There are a few simple things we can do to maximize our MP3 quality, while restricting filesizes.

MP3 Bitrates

As you'll know, you can usually choose from several different "bitrates" when encoding MP3 files. By default most people encode CBR MP3 files (Constant Bit Rate)

A rough CBR MP3 bitrate guide:

128kbps - average, some noticeable quality loss

160kbps - slightly better, but still not perfect

192kbps - very popular tradeoff between quality/size

256kbps - high quality, filesizes getting large

320kbps - excellent quality - huge mp3 filesizes

CBR or VBR?

Another great advance in MP3 encoding technology was the emergence of Variable Bit Rate encoding, or VBR.

Originally most people used Constant Bit Rate (CBR) encoding - this means that the filesize is always 100% dependant on the playtime of the song, as a "constant" amount of file data is encoded regardless of how complex or simple that part of the song is.

This is a wasteful way to do things, think of it this way - when a song gets to a quieter moment, with fewer instruments and no vocals for example, a much lower bitrate is required to continue to sound just as good.

Likewise, when the song reaches a complex part, with a lot of instruments/vocals, the bitrate required to keep that section of song sounding good is much higher, or you will hear a loss of quality.

To get around this, you can now use VBR encoding, which automatically adjusts the bitrate as the file is being encoded, keeping the sound quality high for the listener, but also keeping the filesize under control.

For example, if you were to encode a song at 128kbps VBR, that will be roughly the average. During simple quiet moments of the song, the bitrate might drop to 96kbps, and in the complex parts it might jump up to 192kbps.

End result?

A song which sounds great, with a reasonable filesize.

Unfortunately not all software can encode VBR (though most modern programs can). If you need a free program to encode VBR MP3 files, just download winlame.