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Topic: How to force lowpass above 20.5 kHz for 320 CBR? (Read 11887 times) previous topic - next topic
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How to force lowpass above 20.5 kHz for 320 CBR?

When I put lowpass 16 kHz it works but when I try 22 kHz it never works. It looks like it's limited to 20.5. Any way to bypass this limit?
Doing this in foobar.
Using LAME 3.99.5

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #1 –
Quote from: belushka on
When I put lowpass 16 kHz it works but when I try 22 kHz it never works. It looks like it's limited to 20.5. Any way to bypass this limit?


Why do you want to preserve frequencies (in a lossy format) that cannot be heard by human ears? You will be reducing the quality of the content in the frequency range that can be heard by humans by expending bitrate on ultrasound.
lossyWAV -q X -a 4 -s h -A --feedback 2 --limit 15848 --scale 0.5 | FLAC -5 -e -p -b 512 -P=4096 -S- (having set foobar to output 24-bit PCM; scaling by 0.5 gives the ANS headroom to work)

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #2 –
Quote from: Nick.C on
Quote from: belushka on
When I put lowpass 16 kHz it works but when I try 22 kHz it never works. It looks like it's limited to 20.5. Any way to bypass this limit?


Why do you want to preserve frequencies (in a lossy format) that cannot be heard by human ears? You will be reducing the quality of the content in the frequency range that can be heard by humans by expending bitrate on ultrasound.

The reason why I'm doing this is following:
When using auCDtect to analyze lossless files whether or not they are really lossless I noticed that when I make .flac out of .m4a(320kbps) that has limit at 20.5 kHz it detects it as lossy 100% but when I make a .flac out of .m4a that has 22.5 kHz limit, it detects it as lossless.
So I want to see if it will do the same with .mp3 that has 22.5 kHz limit.

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #3 –
Does it really matter? Attempting to ascertaining whether or not a signal is ‘truly lossless’ is doomed to uncertainty (at least without a verified original to bit-compare against). I’m all for curiosity for its own sake, but is there anything practical to be gained from the test?

Anyway
Quote
when I try 22 kHz it never works. It looks like it's limited to 20.5. Any way to bypass this limit?
Well, this makes sense, assuming you’re talking about 44.1 kHz source files, which you never confirmed. The encoder needs a transition band in which to allow the filter to accelerate its slope at a reasonable rate, to avoid ringing and other undesirable side-effects. 0.05 kHz of bandwidth at 44.1 kHz is far from sufficient. 20 or 20.5 are basically industry standards in this regard. It would make sense if LAME will ignore higher, too high settings.

If you really want to try forcing inadvisable parameters, reading the documentation more thoroughly will suggest some switches that might be able to ‘help’

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #4 –
Quote from: db1989 on
If you really want to try forcing inadvisable parameters, reading the documentation more thoroughly will suggest some switches that might be able to ‘help’

I haven't been able to find anything regarding how to force a lowpass above 20.5 in LAME documentation. Do you know how to do it?

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #5 –
Quote from: belushka on
Quote from: db1989 on
If you really want to try forcing inadvisable parameters, reading the documentation more thoroughly will suggest some switches that might be able to ‘help’

I haven't been able to find anything regarding how to force a lowpass above 20.5 in LAME documentation. Do you know how to do it?


It may well be that you are not able to as it does not make much sense to do so.
lossyWAV -q X -a 4 -s h -A --feedback 2 --limit 15848 --scale 0.5 | FLAC -5 -e -p -b 512 -P=4096 -S- (having set foobar to output 24-bit PCM; scaling by 0.5 gives the ANS headroom to work)

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #6 –
Quote from: Nick.C on
It may well be that you are not able to as it does not make much sense to do so.

so it's impossible to make a lowpass above 20.5 kHz for CBR in LAME?

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #7 –
The cutoff is the middle of the band, not the edge, so 20.5 (or maybe 21.0 if thats allowed) is essentially the same thing as no filter.

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #8 –
The lame command line documentation states:
Code: [Select]
--lowpass      Frequency(kHz), lowpass filter cutoff above freq. 
               Range [0.001..50]kHz or [50..50000]Hz
--lowpass-width
               Frequency(kHz), lowpass window width. 
               Range [0.001..16]kHz or [16..50000]Hz 
               (See further restriction in the detailed explanation)
lossyWAV -q X -a 4 -s h -A --feedback 2 --limit 15848 --scale 0.5 | FLAC -5 -e -p -b 512 -P=4096 -S- (having set foobar to output 24-bit PCM; scaling by 0.5 gives the ANS headroom to work)

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #9 –
I know that for V0 the lowpass is 22 kHz, so why can't it be set for CBR?

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #10 –
Quote from: saratoga on
The cutoff is the middle of the band, not the edge, so 20.5 (or maybe 21.0 if thats allowed) is essentially the same thing as no filter.

Is there any way to make the frequencies go all the way up to 22 kHz in CBR mode?
 

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #11 –
Quote from: belushka on
I know that for V0 the lowpass is 22 kHz, so why can't it be set for CBR?


I haven't tested, but I would expect --lowpass 20.5 and -V0 to have a similar frequency response.  Is this not what you see?

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #12 –
-k used to disable all filters, but it was being abused by folks like yourself, so I believe it was removed.

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #13 –
Quote from: saratoga on
Quote from: belushka on
I know that for V0 the lowpass is 22 kHz, so why can't it be set for CBR?


I haven't tested, but I would expect --lowpass 20.5 and -V0 to have a similar frequency response.  Is this not what you see?

no, when I use -V0, it goes up to 22 kHz, when I use 320 CBR or just put lowpass 20.5 in V0, it goes only up to that.

Quote from: pdq on
-k used to disable all filters, but it was being abused by folks like yourself, so I believe it was removed.

Can you please explain how is setting a different lowpass abuse?

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #14 –
Quote
The reason why I'm doing this is following:
When using auCDtect to analyze lossless files whether or not they are really lossless I noticed that when I make .flac out of .m4a(320kbps) that has limit at 20.5 kHz it detects it as lossy 100% but when I make a .flac out of .m4a that has 22.5 kHz limit, it detects it as lossless.
So I want to see if it will do the same with .mp3 that has 22.5 kHz limit.
I have NOT tried this, but if your goal is to fake-out auCDtect, try an Exciter Effect to add high-frequency harmonics.  (Decompress the MP3, add harmonics, compress to FLAC.) 

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #15 –
Quote from: belushka on
Quote from: pdq on
-k used to disable all filters, but it was being abused by folks like yourself, so I believe it was removed.

Can you please explain how is setting a different lowpass abuse?

I have no problem with setting a sensible lowpass. My own hearing only goes up to 12 kHz so I could adjust the lowpass to significantly shrink my files with no loss in my perceived quality.

The problem is with people who think that NO filtering is an improvement, which it is not. Having a switch that accomplished that was just too tempting for those who were not willing to learn its full effects.

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #16 –
Quote from: pdq on
Quote from: belushka on
Quote from: pdq on
-k used to disable all filters, but it was being abused by folks like yourself, so I believe it was removed.

Can you please explain how is setting a different lowpass abuse?

I have no problem with setting a sensible lowpass. My own hearing only goes up to 12 kHz so I could adjust the lowpass to significantly shrink my files with no loss in my perceived quality.

The problem is with people who think that NO filtering is an improvement, which it is not. Having a switch that accomplished that was just too tempting for those who were not willing to learn its full effects.

Why the hell did they put 22 kHz limit on audio CD if nobody can hear it as you say? Why didn't they put a 20 kHz limit?

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #18 –
Quote from: belushka on
Quote from: pdq on
Quote from: belushka on
Quote from: pdq on
-k used to disable all filters, but it was being abused by folks like yourself, so I believe it was removed.

Can you please explain how is setting a different lowpass abuse?

I have no problem with setting a sensible lowpass. My own hearing only goes up to 12 kHz so I could adjust the lowpass to significantly shrink my files with no loss in my perceived quality.

The problem is with people who think that NO filtering is an improvement, which it is not. Having a switch that accomplished that was just too tempting for those who were not willing to learn its full effects.

Why the hell did they put 22 kHz limit on audio CD if nobody can hear it as you say? Why didn't they put a 20 kHz limit?


Because why not.

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #19 –
Quote from: db1989 on
Just sit back and let other people do that basic bit of web searching on your behalf

cd why 44.1

http://en.wikipedia.org/wiki/44,100_Hz#Why_44.1_kHz.3F
http://www.cardinalpeak.com/blog/why-do-cd...te-of-44-1-khz/
etc.

I know already why, you don't have to tell me... I was asking pdq

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #20 –
Well, at least now we know your questions are sarcastic and we don’t need to waste our time answering them properly

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #21 –
I think the OP's problem is you stumbled upon the -Y switch. Quoting the HA wiki:
Quote
The -Y switch can only be activated in VBR mode. By default, -V 3 to -V 9 use -Y. -V 0, -V 1, and -V 2 do not. Consequently, adding -Y is only useful for the highest three VBR settings.
This is because in CBR and ABR modes, the encoder uses -Y implicitly. Specifically, LAME targets a given bitrate, and adjusts the quantization steps until that target is reached.


http://wiki.hydrogenaudio.org/index.php?title=LAME_Y_Switch

How to force lowpass above 20.5 kHz for 320 CBR?

Reply #22 –
Quote from: belushka on
Quote from: pdq on
Quote from: belushka on
Quote from: pdq on
-k used to disable all filters, but it was being abused by folks like yourself, so I believe it was removed.

Can you please explain how is setting a different lowpass abuse?

I have no problem with setting a sensible lowpass. My own hearing only goes up to 12 kHz so I could adjust the lowpass to significantly shrink my files with no loss in my perceived quality.

The problem is with people who think that NO filtering is an improvement, which it is not. Having a switch that accomplished that was just too tempting for those who were not willing to learn its full effects.

Why the hell did they put 22 kHz limit on audio CD if nobody can hear it as you say? Why didn't they put a 20 kHz limit?


The limit on audio CDs is not really 22KHz.  Thats just (approximately) half the sampling rate.  Pretty much no practical DAC can play back a tone at 99.77% of the Nyquist rate.  The typical limit is more like 90-95% (with newer devices being closer to the upper end of that limit).  Hence, they left a couple kHz of transition band with the expectation that audio would extend no higher than 18-20kHz.

Quote from: belushka on
I know already why, you don't have to tell me... I was asking pdq


I don't think you do.