Is AAC-HE at 128 good idea?
Reply #10 – 2013-06-04 19:59:05
OK, let's see...For stereo 48 ABR 128, would I be better off using HE or LC? These are mainly audio of documentaries which naturally are mostly narration with the odd background music and effects. I suggest you use AAC LC. HE-AAC will give you no advantage at this bitrate. Speaking of compatibility, it would be nice if Kohlrabi could point out some hard-/software which still has problems with HE-AAC decoding, so we can contact the developers (btw, have you always been Super Moderator, Kohlrabi?)with regard to the original question, I am under the impression that AAC-HE can only be used up to 80 kbps... Not having read the standard, I don't know whether it's possible to make an encoder that does SBR at >80kbps... There is absolutely no such restriction in the AAC standard . In fact, IIRC Winamp 5.63 (and higher) can do up to 128-kbps HE-AAC in CBR mode. Maybe someone can try it out and report. This brings me to the last point:"If not, what would limit it technically speaking?" Uh, the fact that it's not coding half the bandwidth at all? Again, this is not a limitation of the standard, it's an encoder design decision. I thought I already made this clear in another thread once, but I'm happy to repeat: there's a mode called "downsampled SBR", in which you can move the SBR start frequency above half the input signal bandwidth. For example, with 44.1- or 48-kHz audio input, you could let SBR code only the frequencies above 16 kHz or so. Such a setting will be transparent for many people (assuming the core bit-rate is high enough). Fraunhofer's encoder supports downsampled SBR, but that mode might not (yet) be available in Winamp, I don't remember. Chris