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Handling high frequencies, Please help pushing my tiny MP3 know-how
post May 16 2003, 04:03
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Posts: 127
Joined: 19-April 03
Member No.: 6057

Hi! - I had thought... But first tell me please:

1.) --ns-sfb21 # : Using a higher the value # will DEcrease all the high frequencies of the scale factor band 21
(above 16 kHz) in my MP3, right ?

2.) The "polyphase lowpass filter transition band : 19383-19916 Hz" will use a 'dynamical' lowpass filter border
(here between 19,4 and 19.9 kHz) depending on any other encoding restriction (eg. space / filesize), ok ?

Now, would create a Lame setting with ...
case A) "-- lowpass 19.3 --lowpass-width 0.5 --ns-sfb 2.5" (=> polyph. LP filter trans. band: 18.7-19.9kHz)
... equvalent results like...
case B) "-- lowpass 19.6 --lowpass-width 0.3 --ns-sfb 3" (=> polyph. LP filter trans. band: 19.4-19.9kHz)
... ???

Well, You see surley, case B) is very similar to the consequences of "--alt-preset-extreme (-Z)" setting.

But this should be no general critism on the ape setting. I wonder simply - guessed 1) and 2) are true -
why reducing ALL high frequencies by using a quite high lowpass filter [=>B)] insteed of a 'more untouched'
scalefactor band 21 in combination with a more dynamic polyph. LP filter trans. band [=>A)] ...?
...specially respecting the fact than people can here a sound at 17 kHz rather than one at 19.5 kHz.

I hope anyone could check this out - I would be very interessed on his opinion.

Bye, 384kbps
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