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Topic: Why does FDK documentation ask for 48khz at really high bitrates (Read 2000 times) previous topic - next topic
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Why does FDK documentation ask for 48khz at really high bitrates

According to the page on FDK AAC in this site's wiki, FDK's documentation suggests that at bitrates above 320kbps for LC-AAC, and 64kbps for HE-AAC, 48khz sounds better than 44.1khz.

What is the logic behind this? Shouldn't less samples always be easier for the encoder?

Re: Why does FDK documentation ask for 48khz at really high bitrates

Reply #1
I guess that is slightly easier to work with 48KHz than 44.1KHz.
48000 is a very round number, and it is easily dividable. That's why Opus uses 48KHz. Anyway, at some point there's no more option than increase sampling to "increase" quality (you can go up to 96 KHz with most common AAC encoders excepting Apple-AAC without SBR).

Re: Why does FDK documentation ask for 48khz at really high bitrates

Reply #2
According to the page on FDK AAC in this site's wiki, FDK's documentation suggests that at bitrates above 320kbps for LC-AAC, and 64kbps for HE-AAC, 48khz sounds better than 44.1khz.

What is the logic behind this? Shouldn't less samples always be easier for the encoder?

I think that with the cheap devices that are sold today 48 kHz is always the best choice. Keep in mind that at the input you always have a low-pass filter at 20 kHz (or even less).

Also since USB exists the oscillators in computers are always exact multiples of 48 kHz.

Re: Why does FDK documentation ask for 48khz at really high bitrates

Reply #3
I guess that is slightly easier to work with 48KHz than 44.1KHz.
48000 is a very round number, and it is easily dividable. That's why Opus uses 48KHz. Anyway, at some point there's no more option than increase sampling to "increase" quality (you can go up to 96 KHz with most common AAC encoders excepting Apple-AAC without SBR).
So why does FDK ask for 48khz only at high bitrates instead of all?

 

Re: Why does FDK documentation ask for 48khz at really high bitrates

Reply #4
So why does FDK ask for 48khz only at high bitrates instead of all?
Why does Porcus ask for sub-bass at only at high speaker budgets, instead of all?

Because it takes more of the available resources, and then other more significant elements might have to go.
48 kHz takes up more of the bitrate. Whatever the bitrate (and/or other computational resources in scarcity) might be, you want a lossy encoder to get the signal as good as possible. What is less likely to be audible (or annoying) goes out first.