Originally posted by Dave Abrey
At a given bit rate (lets say 192 Kbps), how does the file size for AAC compare with MP3 for the same song? I'm trying to work out what size HD and iPod I'd need to get my entire CD collection encoded.
at a given bit rate, file size is exactly the same. it's the number of bits per second. the size still might vary slightly with varying settings... you can rip mp3 at "variable bit rate" (VBR) which means it varies the bitrate up and down slightly according to the complexity of the music, using lower quality when the music is less complex and higher quality when it is more complex. AFAIK m4p always does this and is better at it. but the file sizes will still be very close.
the question to ask is which bitrate should you use. apple claims that m4p is basically near cd quality at 128kbs. i think it definitely sounds much better than mp3 at this bitrate, but many people have reported strange artifacts in m4p (crackling, incorrect stereo panning, et cetera), and i have heard some of these and am still investigating the issue before i go all out and re-rip my whole library. the lowest rate at which i would suggest ripping mp3s is 160, and for music like classical or jazz, 192. my whole library is ripped at around 224 mp3. (with vbr turned on... the settings are kind of confusing, and i'm still not sure if changing the bitrate setting makes any difference when using vbr... does anyone have an answer to this question?).
that said, when my g5 comes i am almost certainly going to drag my itunes library into the trash and re-rip my entire cd collection at 160 m4p (my ipod is only 5 gigs so it will be a big space savings).