default lowpass frequencies in apple encoder

[wyup]

I would like to know which are the default lowpass frequencies used in cbr and vbr profiles to be able to adjust --lowpass option in command line. Lame and fraunhofer encoders specify these in hydrogenaudio wikis, as it is very important to know where are lowpass filters to choose performance in high bitrates.

[nu774]

--lowpass has nothing to do with the Apple encoder's bandwidth. If you want to know encoder's bandwidth, just try encoding and inspect the output yourself. There's no way to control the bandwidth of Apple's encoder. --lowpass will just filter signal before passing it to the encoder. So, it is an additional layer provided by qaac, and you can just make bandwidth narrower than the encoder's default.

[wyup]

I know, it works the same in lame or fdk. But I'd rather save the effort of inspecting the output of various bitrates if it's known in advance. E.g: say I knew apple lowpassed 128 at 17Khz by default like fdk, I might or not choose to lowpass further in options. And I understand better the internal choice of the encoder to compare.

[Dendraspis]

Interesting, I never found informations that (Apple) AAC Encoder would limit the bandwidth. Has anybody some papers or websites where these informations can be found? I would really appreciate it!

Sorry for being maybe off-topic.

[ValZapod]

lowpassed 128 at 17Khz by default like fdk, I

And? Note: libfdk_aac defaults to a low-pass filter of around 14kHz (​details). If you want to preserve higher frequencies, use -cutoff 18000. Adjust the number to the upper frequency limit only if you need to; keeping in mind that a higher limit may audibly reduce the overall quality.

https://trac.ffmpeg.org/wiki/Encode/AAC