Hydrogenaudio Forums > Lowpass Bug?

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Oge_user

Jun 16 2003, 07:05

If I use --lowpass 20 or --lowpass 20,5 Lame reports the same transition band..

--lowpass 20000

CODE

C:\audiograbber\Test>LAME Fighter.wav --lowpass 20000
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), SIMD
Using polyphase lowpass filter, transition band: 20094 Hz - 20627 Hz
Encoding Fighter.wav to Fighter.wav.mp3
Encoding as 44.1 kHz 128 kbps j-stereo MPEG-1 Layer III (11x) qval=5
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
150/9532 ( 2%)| 0:01/ 1:30| 0:01/ 1:30| 2.7401x| 1:29

--lowpass 20500

CODE

C:\audiograbber\Test>LAME Fighter.wav --lowpass 20500
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), SIMD
Using polyphase lowpass filter, transition band: 20094 Hz - 20627 Hz
Encoding Fighter.wav to Fighter.wav.mp3
Encoding as 44.1 kHz 128 kbps j-stereo MPEG-1 Layer III (11x) qval=5
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
150/9532 ( 2%)| 0:01/ 1:37| 0:01/ 1:37| 2.5444x| 1:36

Same problem with 3.92, both CBR and VBR..
Is it a bug?

Lev

Jun 16 2003, 07:20

QUOTE

20094 Hz - 20627 Hz

Yep, I can believe that.

Ssshhhhh! Keep it quiet until someone claims that a lowpass of 20khz is not enough, that they cant hear the top end, and yet, with 20.5khz, that issue is gone :-D

CiTay

Jun 16 2003, 08:22

QUOTE(Oge_user @ Jun 16 2003 - 03:05 PM)

Same problem with 3.92, both CBR and VBR..
Is it a bug?

No, this is normal. LAME has some lowpass thresholds, anything above or below that will be rounded up or down. It's not as flexible as the --lowpass switch suggests.

Oge_user

Jun 16 2003, 08:43

The output should be different isn't it?

Jan S.

Jun 16 2003, 09:03

QUOTE(Oge_user @ Jun 16 2003 - 04:43 PM)

The output should be different isn't it?

As far as I have understood it should be completely the same. Why don't you just do a file compare?
They should be identical.

Oge_user

Jun 16 2003, 09:36

I've compared the files, they are identical..

When (for example) lowpass 19 and 19,5 produce different output..

Gambit

Jun 18 2003, 00:49

QUOTE(CiTay @ Jun 16 2003 - 03:22 PM)

QUOTE(Oge_user @ Jun 16 2003 - 03:05 PM)

Same problem with 3.92, both CBR and VBR..
Is it a bug?

No, this is normal. LAME has some lowpass thresholds, anything above or below that will be rounded up or down. It's not as flexible as the --lowpass switch suggests.

And the steps/values you can use with the lowpass option are:

21.8
21.1
20.4
19.6
18.9
18.2
17.5
16.8
16.1
15.4
14.7
14.0
13.2
12.5
11.8
11.1
10.4
9.7
9.0
8.3
7.6
6.8
6.1
5.4
4.7
4.0
3.3
2.6
1.9
1.2
0.4

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