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Lossy Audio Compression => MP3 => MP3 - Tech => Topic started by: Linuxx on 2018-04-29 14:15:26

Title: Question about lame MP3 and low pass filter
Post by: Linuxx on 2018-04-29 14:15:26
Hi guys, I use lame mp3 + EAC to rip my cd. I use the command line --preset extreme that include a low pass filter 22.1 kHz. I noticed that some tracks are ripping with a transion band of 16 kHz. Is it normal? The song is original mastered at 16 kHz?
Title: Re: Question about lame MP3 and low pass filter
Post by: magicgoose on 2018-04-29 19:08:32
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The song is original mastered at 16 kHz?
You can check it if you rip to a lossless format and analyze it. With lossy it's hard to tell if it was there before or not.

Quote
Is it normal?
Yes, it is normal, especially for MP3.

Quote
I use the command line --preset extreme that include a low pass filter 22.1 kHz
Why not simply -V 0 instead?
Title: Re: Question about lame MP3 and low pass filter
Post by: Linuxx on 2018-04-30 01:25:20
Quote
Why not simply -V 0 instead?

Because preset extreme include this command: -m j -V 0 -q 0 -lowpass 22.1 --vbr-new -b 32

I checked source Wav and I see this:

(http://oi63.tinypic.com/ka0bd2.jpg)

And this is mp3 file:

(http://oi67.tinypic.com/11v1b8k.jpg)
Title: Re: Question about lame MP3 and low pass filter
Post by: magicgoose on 2018-04-30 08:21:53
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Because preset extreme include this command: -m j -V 0 -q 0 -lowpass 22.1 --vbr-new -b 32

…And why do you need any of that?
`--vbr-new` should be the default in recent versions of LAME.
Same for `-m j`.
-b 32 is pointless, as it's the lowest possible bitrate anyway. VBR mode already has no reason to use anything higher when encoding silence.

The questions remains for `-lowpass 22.1` and `-q 0`: why do you think it's needed?

Also please upload pictures to a host that supports HTTPS, otherwise they won't be displayed here on most modern browsers because of mixed content policy. https://developer.mozilla.org/en-US/docs/Web/Security/Mixed_content
Title: Re: Question about lame MP3 and low pass filter
Post by: Linuxx on 2018-04-30 11:05:35
I can't edit the post with image....if you want I past image's link. About command line, I repeat that preset extreme include all those built-in command. It's a dev lame option. But the point is the lowpass filter, if lame cut some frequency from original source.

Here's wave file:

http://oi63.tinypic.com/ka0bd2.jpg

And here's mp3 file:

http://oi67.tinypic.com/11v1b8k.jpg
Title: Re: Question about lame MP3 and low pass filter
Post by: magicgoose on 2018-04-30 11:19:56
But the point is the lowpass filter, if lame cut some frequency from original source.
So, why do you want to adjust the lowpass filter settings?
Unless you are supernaturally sensitive to these frequencies, it will only reduce the quality. Default LAME settings are a result of a lot of tuning standing on extensive listening tests.
Title: Re: Question about lame MP3 and low pass filter
Post by: magicgoose on 2018-04-30 11:50:32
https://wiki.hydrogenaud.io/index.php?title=High-frequency_content_in_MP3s
an obligatory article on this topic
Title: Re: Question about lame MP3 and low pass filter
Post by: Linuxx on 2018-04-30 13:57:05
But the point is the lowpass filter, if lame cut some frequency from original source.
So, why do you want to adjust the lowpass filter settings?
Unless you are supernaturally sensitive to these frequencies, it will only reduce the quality. Default LAME settings are a result of a lot of tuning standing on extensive listening tests.

I think you don't understand....I don't touch low pass filter. Preset extreme has a low pass default of 22.1kHz (and I know that I'm unable to hear at 22.1kHZ). My question was if is it normal that some songs are cutted at 16kHz frequency and others not.
Title: Re: Question about lame MP3 and low pass filter
Post by: pdq on 2018-04-30 14:10:05
The whole point of perceptual compression is that if you can't hear it, don't waste bits on it.

The encoder looks at high frequencies, decides that they are being masked by louder lower frequencies, and voila, they are gone!
Title: Re: Question about lame MP3 and low pass filter
Post by: magicgoose on 2018-04-30 14:13:57
Yes, it's perfectly normal for LAME; lowpass filter is not the only part of it that removes frequencies, there's also psy model that decides which frequencies aren't perceivable and it decides that >16k frequencies are unnecessary more often than not.
Title: Re: Question about lame MP3 and low pass filter
Post by: DVDdoug on 2018-04-30 16:09:19
I've never tried this but just as an experiment, you could try high-passing at 10-15kHz (with Audacity or your favorite audio editor).    You might want to boost the level too since there won't be much amplitude remaining.    There should be less masking and LAME should see those high frequencies as more important.
Title: Re: Question about lame MP3 and low pass filter
Post by: Linuxx on 2018-05-01 02:07:58
Ok guys, thanks a lot!  Now I understood that it's normal. I also think that it's time to move with FLAC format to get a very good quality to use with serious HI-FI.
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