Originally Posted by bikefixe
I assumed, perhaps incorrectly, that VBR = variable bit rate, and that if you rip at 256 VBR, 256 is the max bitrate, and for sections of lower complexity in the music, the actual bitrate will be lower than that max. Anyone care to confirm or educate me?
Very simple, VBR is variable bit rate so you can never expect or predict its actual bitrate before ripping. Imagine an audio file is made up from very small audio chunks called frames, each frame would have it own bitrate when recorded, when chosen to encode with VBR, the encoder knows that it has to choose which bitrate is best to use with each frame according to the required value of data (lower value will be applied if there's not much audio going on and boost it up when needed), hence the final bitrate is unpredictable. That said, saying 256 VBR is maxed at 256 is somewhat contradicting, only because with a real mechanism of VBR encoding, as in dbPoweramp, you can't choose the the desired bitrate to rip with, but will rather see settings like -V0 or V0.5....which indicates how high the outcome quality will be, and is rounded as close to 240kbps VBR (as good as 320kbps CBR) for MP3 but not always close.
Some says iTunes VBR might use a different method to encode, in fact we doubt that they use ABR (similar to VBR but with more predictable bitrate) for audio encoding. I've tested some of the songs ripped from my CD and lossless format to AAC with this VBR setting on, 4 out of 5 I couldn't guess the average or constant bitrate of the song after ripping. So saying they're using ABR still a vague theory, yet the ripped quality is exceptionally good so I don't care that much.
Long story short, I think Apple do have a point on navigating people to trust in their music store, for most is still better than 320kbps MP3 if you're not comparing them directly to CD or Vinyl, which is good enough for most digital audio player and end consumer. I used to think 320kbps MP3 is superior but after researching and learning myself, now my music library is alll AAC and ALAC/FLAC at least I'm ensured that my audio quality is not cut off at the very limit of 20kHz as in MP3..the rest is down to your personal choice and what you think is best for your quality demand :D