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nu774 / qaac

CLI QuickTime AAC/ALAC encoder
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default lowpass frequencies in apple encoder #70

Open wyup opened 4 years ago

wyup commented 4 years ago

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 commented 4 years ago

--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 commented 3 years ago

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 commented 3 years ago

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.