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How to prevent lame from cutting the spectrum?
mzso
post Sep 15 2011, 13:35
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Hi!
I tried increasing the lowpass value, but it didn't do anything useful. It only cut almost everything when I set it too high. But it never would leave the upper portions alone.
Also what's --lowpass-width supposed to do?
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mixminus1
post Sep 15 2011, 14:16
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Why do you want to do this?


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pdq
post Sep 15 2011, 14:31
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As I understand it, the option to eliminate any lowpass filtering was removed in current versions of LAME, because this is generally a bad idea. You might try older versions where this was still possible.

Edit: I think what happened when you set the lowpass too high was it switched from assuming Hz to assuming kHz.

Edit2: I think I got that backwards - below 20 something it assumes this is kHz, above it assumes Hz. To be safe, always specify in Hz so there is no confusion.

This post has been edited by pdq: Sep 15 2011, 14:52
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Northpack
post Sep 15 2011, 15:12
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QUOTE (mzso @ Sep 15 2011, 13:35) *
I tried increasing the lowpass value, but it didn't do anything useful.

Even if it worked it wouldn't do anything useful but possibly lower the perceptual quality of your MP3s. If you absolutely have to avoid low pass filtering, for whatever reason, you should use lossless encoding anyway.

This post has been edited by Northpack: Sep 15 2011, 15:12
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lvqcl
post Sep 15 2011, 16:02
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To disable lowpass filter, use --lowpass -1 switch. But chances are high that LAME will remove high frequencies anyway because of its psychoacoustic model.
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mjb2006
post Sep 16 2011, 00:44
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The higher-frequency content you're seeking to preserve tends to be more noise-like, thus more difficult to encode...your efforts to preserve it may well starve the rest of the spectrum of bits, impacting the quality at frequencies you're much more likely to notice. MP3 in particular also has difficulty with resolution above 16 kHz; Google "sfb21". At higher bitrates, depending on the characteristics of the audio and the psychoacoustic model, LAME will strategically allow higher-frequency content to be preserved. If you're not getting it, you don't need it. If you still think you need it, abandon MP3 and switch to a lossless format.
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mzso
post Sep 16 2011, 09:12
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Thanks for the info guys.
QUOTE (lvqcl @ Sep 15 2011, 17:02) *
To disable lowpass filter, use --lowpass -1 switch. But chances are high that LAME will remove high frequencies anyway because of its psychoacoustic model.

It still cuts. Even with cbr320.
QUOTE (mixminus1 @ Sep 15 2011, 15:16) *
Why do you want to do this?

I was trying to get the best the best out of mp3. Highest bitrate no spectrum butchering and whatnot.
QUOTE (mjb2006 @ Sep 16 2011, 01:44) *
The higher-frequency content you're seeking to preserve tends to be more noise-like, thus more difficult to encode...your efforts to preserve it may well starve the rest of the spectrum of bits, impacting the quality at frequencies you're much more likely to notice. MP3 in particular also has difficulty with resolution above 16 kHz; Google "sfb21". At higher bitrates, depending on the characteristics of the audio and the psychoacoustic model, LAME will strategically allow higher-frequency content to be preserved. If you're not getting it, you don't need it. If you still think you need it, abandon MP3 and switch to a lossless format.

Well mp3 isn't my format of choice. Its not even my lossy format of choice. But since mp3 is pretty much the norm and others are poorly supported... For example I didn't find a free hosting service that hosts vorbis (not to mention flac) and can play them back in the browser, only mp3. Its convenient for showing people something you like.
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db1989
post Sep 16 2011, 11:14
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QUOTE (mzso @ Sep 16 2011, 09:12) *
QUOTE (mixminus1 @ Sep 15 2011, 15:16) *
Why do you want to do this?

I was trying to get the best the best out of mp3. Highest bitrate no spectrum butchering and whatnot.
Needlessly diverting bits to frequencies that you will never hear and thus degrading the overall quality of the bitstream including those lower frequencies that you can hear. Right!
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dhromed
post Sep 16 2011, 12:15
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QUOTE (db1989 @ Sep 16 2011, 12:14) *
Right!

It's not unreasonable for people who aren't familiar with the internal workings of mp3 to assume that dropping things like lowpass will improve the sound quality and get them the "best possible mp3", even though in fact the opposite happens (regardless of audibility).

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Northpack
post Sep 16 2011, 12:36
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QUOTE (mzso @ Sep 16 2011, 08:12) *
I was trying to get the best the best out of mp3. Highest bitrate no spectrum butchering and whatnot.

You will achieve exactly the opposite of your intention. You will make your MP3s sounding worse when you force the encoder to keep all frequencys up to 22kHz.

See: there are many very clever people involved in the development of MP3 encoders. Do you really think that anything the encoder does - after more than 10 years of development - isn't well-founded and optimized for best possible quality? Do you really assume you know better than them?
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mzso
post Sep 16 2011, 12:40
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QUOTE (db1989 @ Sep 16 2011, 12:14) *
QUOTE (mzso @ Sep 16 2011, 09:12) *
QUOTE (mixminus1 @ Sep 15 2011, 15:16) *
Why do you want to do this?

I was trying to get the best the best out of mp3. Highest bitrate no spectrum butchering and whatnot.
Needlessly diverting bits to frequencies that you will never hear and thus degrading the overall quality of the bitstream including those lower frequencies that you can hear. Right!

I actually tested it. could definitely hear above 19k. Plus vorbis cuts above 20k even at q5 and doesn't cut anything at q7. Also that's why I combined it with the highest bitrates.
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Northpack
post Sep 16 2011, 12:46
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QUOTE (mzso @ Sep 16 2011, 12:40) *
I actually tested it. could definitely hear above 19k. Plus vorbis cuts above 20k even at q5 and doesn't cut anything at q7. Also that's why I combined it with the highest bitrates.

I'm afraid you've missed the point. It doesn't matter what you can hear. I can hear up to 20kHz, when listening to a sine wave signal, yet I can't tell the difference between music containing frequencies up to 22kHz and the same track low-passed to 17kHz, when conducting a proper (ABX) listening test. And this is not a singular deficiency of mine but a psychoacoustic principle MP3 and other lossy encoding technologies take advantage of.

Vorbis however is based on a very different approach than MP3 and is much more efficient at encoding high frequency content above 16kHz, thus vorbis can afford the "luxury" of keeping those frequencys - MP3 can't.

This post has been edited by Northpack: Sep 16 2011, 12:59
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halb27
post Sep 16 2011, 13:11
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I do second this.
I don't think in real life music a lowpass of 17.5 or even 16.7 kHz is ABXable with the exception of extremely few listeners.
And Lame's standard lowpass is higher with the highest VBR modes.


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ShotCaller
post Sep 17 2011, 20:38
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I agree with all the above statements that what you are trying to do is probably not going to improve your encode quality. However, LAME 3.99 beta now uses a lowpass filter at 21.5 kHz for VBR, so it seems the LAME developers have an interest in trying to preserve these high frequencies, for whatever reason...
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db1989
post Sep 17 2011, 20:50
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QUOTE (ShotCaller @ Sep 17 2011, 20:38) *
LAME 3.99 beta now uses a lowpass filter at 21.5 kHz for VBR
Of all levels?
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ShotCaller
post Sep 17 2011, 21:59
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At -V 0. Didn't try the others, but I assume they are lower.
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mzso
post Sep 18 2011, 00:34
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QUOTE (ShotCaller @ Sep 17 2011, 22:59) *
At -V 0. Didn't try the others, but I assume they are lower.

It even cuts lower with cbr320.
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lvqcl
post Sep 18 2011, 00:46
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There are more ways than one to kill a cat lower the quality of MP3 files.
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greynol
post Sep 18 2011, 01:02
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That reminds me of Carter on Hogan's Heroes saying it was "easy as cake".

This post has been edited by greynol: Sep 18 2011, 02:15


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Satellite_6
post Sep 18 2011, 01:44
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QUOTE (mzso @ Sep 17 2011, 19:34) *
QUOTE (ShotCaller @ Sep 17 2011, 22:59) *
At -V 0. Didn't try the others, but I assume they are lower.

It even cuts lower with cbr320.



I though that 320 cuts off at 20k, while -v0 cuts off at 19k (not that it matters).

Can someone provide a link?


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ShotCaller
post Sep 18 2011, 04:10
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Uh, you guys are forgetting I am talking about 3.99 beta not 3.98.4

By the way, -V 0 in 3.99 beta actually has a lowpass filter set at 22.1 kHz. -V 1 is at 19.5 kHz (.5 kHz higher than in 3.98.4) -V 2 is at 18.5 kHz and -b 320 is at 20.5 kHz (both the same as 3.98.4)
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mzso
post Sep 18 2011, 09:59
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QUOTE (ShotCaller @ Sep 18 2011, 05:10) *
Uh, you guys are forgetting I am talking about 3.99 beta not 3.98.4

By the way, -V 0 in 3.99 beta actually has a lowpass filter set at 22.1 kHz. -V 1 is at 19.5 kHz (.5 kHz higher than in 3.98.4) -V 2 is at 18.5 kHz and -b 320 is at 20.5 kHz (both the same as 3.98.4)

No I didn't. I just tried CBR320 and V1 with it. And it only preserved the spectrum with V0.
QUOTE (Satellite_6 @ Sep 18 2011, 02:44) *
I though that 320 cuts off at 20k, while -v0 cuts off at 19k (not that it matters).

Can someone provide a link?

You can find the beta here: http://www.rarewares.org/mp3-lame-bundle.php
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db1989
post Sep 18 2011, 12:23
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QUOTE (ShotCaller @ Sep 18 2011, 04:10) *
By the way, -V 0 in 3.99 beta actually has a lowpass filter set at 22.1 kHz. -V 1 is at 19.5 kHz (.5 kHz higher than in 3.98.4) -V 2 is at 18.5 kHz and -b 320 is at 20.5 kHz (both the same as 3.98.4)
See, your initial statement could have been (mis?)construed as reporting that all VBR modes of LAME 3.99b lowpass at 21.5 kHz, which I doubted.
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ShotCaller
post Sep 18 2011, 18:35
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Ok
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arfgh
post Dec 7 2011, 15:39
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as i have seen at the moment, only lame 3.93.1 disable completly the lowpass with the switch -k, that now isnt used.
With lame 3.99.3 can be disabled with -lowpass -1, but 21,9 khz
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