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Topic: Why do some encoders use really specific lowpass values? (Read 259 times) previous topic - next topic
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Why do some encoders use really specific lowpass values?

Some encoders seem to use really specific lowpass values. For example, the EZ CD converter's version of FDK AAC uses a lowpass value of 15.7khz for 128kbps CBR, and 17.2khz for 160kbps. Why are these specific values used, instead of just 16khz and 17khz? You also see this in LAME too. They use 15.1khz for 96kbps instead of just 15khz.

https://www.poikosoft.com/ezcd-fraunhofer-fdk-aac-encoder

Were these values picked algorithmically? Is the lowpass filter not 100% accurate? or is there another reason?
 

Re: Why do some encoders use really specific lowpass values?

Reply #1 –
https://wiki.hydrogenaud.io/index.php?title=Fraunhofer_FDK_AAC#Bandwidth - not sure about EZ CD converter having its own customizations

as for why, maybe a good place to start is the source code, then maybe there is git blame (or equivalent) and maybe more context in the commits, also maybe asking the authors of those commits nicely can reveal some more context
a fan of AutoEq + Meier Crossfeed