"Knife, this is Variable"

"Knife, this is Variable." That's a line from a Tom Clancy book. It has nothing to do with this post.

If you are curious about audio compression, it is worth compressing some of your favorite music with a variable compression rate. Take your favorite encoder and set it to "VBR 100", which means "keep this music as close to the original as possible." It's an interesting experiment, because, for instance, the highest constant bit rate (CBR) that Windows Media allows is 192 kbps, but if you use VBR 100, the encoder will decide to encode music at up to 320 kbps!

You're more likely to have an mp3 encoder and you can do the same with that - set it to variable rate encoding at 100% and then play the file in WinAmp. You can watch the bit rate go up and down with the music.

It's tempting to encode everything with VBR100 and get the best sounding music you can get. The reason I don't is that VBR is a hack (a brilliant hack) that was invented by Real and doesn't work in all players. My minidisc software (SonicStage - what crap) in particular can't stand mp3 files that are encoded at more than 256 kbps and a VBR file is likely to jump up over that.

Also, every mp3 player I have seen can't seek accurately in the file, because the variable sized packets of encoded information make it impossible for it to calculate the correct location in a file. That gets annoying.

I've found that 160 kbps mp3 files rarely have artifacts that you would notice in everyday use. 160 used to be my default encoding rate but I've switched to encoding at 192 kbps for mp3 as my default because I feel it gives me some headroom in case I want to edit a file once or twice, which will cause recompression. For professional work, I encode at 192 kbps wma, which sounds terrific.