AAC/m4a bit-rate question

[matt_t]

Does AAC/m4a in VBR mode have an upper bit-rate limit for each Quality setting, in the same way as LAME MP3 VBR has an upper limit of 320kbps?

Specifically I'm interested in the .55/.6/.65 sort of range, or rather, what's the highest Quality setting which will never exceed 320kbps?

Anyone know if there's a chart of this anywhere?

Thanks.

[Spoon]

Not sure, I would guess each mode would have quality contraints to avoid very high bit rates.