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Topic: Do lowpass filter values have to be fixed to boundaries? (Read 233 times) previous topic - next topic
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Do lowpass filter values have to be fixed to boundaries?

I know that AAC seperates audio into frequency bands and gives priority to bands based on which frequency ranges the human ear would be most likely to identify quality loss in.

But if I set the lowpass filter on an encoder in the middle or on the edge of one of these bands, could it cause issues like ringing artifacts?

Re: Do lowpass filter values have to be fixed to boundaries?

Reply #1 –
Low pass filters do not have a specific cut off frequency, they have a transition band where attenuation gradually increases.  Since attenuation gradually increases with increasing frequency, the alignment with individual MDCT bands is not important.
 

Re: Do lowpass filter values have to be fixed to boundaries?

Reply #2 –
Quote from: saratoga on
Low pass filters do not have a specific cut off frequency, they have a transition band where attenuation gradually increases.

Many encoders employ cutoffs that appear to be as sharp as they can be. This is easily verifiable by looking at the spectrograms.