I searched through the forum and found that formula to compute the bitrate for 5.1 files :
bit rate = 2 x stereo bit rate for same quality + 1 mono bit rate for same q + X, where X is only few kb/s for LFE...
I have encoded ac3 files to 5.1 aac using oagmachine and lastest nero dlls using vbr he aac (50 - 70 kbps) profile.
With this profile i expect a 125 to 175 kbps file (which I know is poor quality..)
but my file is around 230 kbps (which is enoug quality i think) which would correspond to a 92 kbps profile in nero encoder.
Do I make a mistake in my computation ???
ex : 176kbps=2*70+35+1
Do I make a mistake in my computation ???
I don't think so...This is simply the beauty of VBR
In fact, the bitrate depends on many things : the kind of source, the "style" too (concert, movie, etc...).
edit : and the formula applies more to a codec with a cbr mode. Well...it's just an assumption. maybe i'm wrong.
thanks kurtnoise for your answer !
In fact the ac3 track is from star wars episode IV (la guerre des étoiles quoi)