Quote:
Originally Posted by ffdshow
128K AAC (with iTunes), it's better than nero or faac, at least it was the case in my tests of last year.
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Well thats also one of the main reasons few people care about iTunes encoder. It is CBR only and if I recall correctly only does 2 channels (or maybe they finally added 5.1 support, I don't recall remember). In this situation it is particularly useless and I would say in most others it is as well. VBR is quite useful in maintaining a certain quality level and also most importantly efficiently using bits.
Since you are encoding from a 5.1 source it would most likely be best to use AAC over Vorbis. Especially if you are going for a low filesize in the end. Since Vorbis has no lossy channel coupling it should not be able to compress as well as AAC per a given quality level. All you are left to do is choose your AAC encoder, however most are 2ch only or CBR only. I think most people would point to Nero AAC which has the most AAC features as well as having the best VBR encoder.
Edit: I could be running off old info for all the iTunes stuff, but back in the day their encoder was extremely limited and Nero was the only useful choice.