HydrogenAudio

Lossy Audio Compression => MP3 => MP3 - Tech => Topic started by: 2Bdecided on 2003-03-24 16:01:32

Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-24 16:01:32
I'm sure this has been asked before, but I can't find it, and it's not in the FAQ (it should be - please!)

On which samples is --alt-preset extreme audibly better than --alt-preset standard.
On which samples is --alt-preset insane audibly better than --alt-preset extreme.
On which samples is --alt-preset insane not transparent?

Cheers,
David.
Title: samples where aps or ape has a problem
Post by: Wombat on 2003-03-24 17:40:37
There are some,

http://www.hydrogenaudio.org/forums/index....ST&f=16&t=4687& (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=4687&)

http://www.hydrogenaudio.org/forums/index....=ST&f=16&t=791& (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=791&)

These i found by just looking into the mp3 - General forum.

You may find more

Wombat
Title: samples where aps or ape has a problem
Post by: Pio2001 on 2003-03-24 21:11:38
Quote
On which samples is --alt-preset insane not transparent?

For me, Badvilbel (by far), and Drone (barely).
Title: samples where aps or ape has a problem
Post by: KikeG on 2003-03-24 22:12:05
For me, the trumpets.wav sample sounds much more transparent with --api than with --aps or --ape, both of which sound very similar and are not transparent.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-25 16:25:37
Thank you all for your responses. I went hunting and listening, and even found another one. To summarise, with --alt-preset standard, I hear the following:


awe22_20sec
http://www.hydrogenaudio.org/forums/index....=ST&f=16&t=2444 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=2444)
ABX 16/16 - the drum beats near the end have added noise

badvilbel
http://www.audio-illumination.org/forums/i...=ST&f=16&t=1059 (http://www.audio-illumination.org/forums/index.php?act=ST&f=16&t=1059)
I (unlike most other people) don't hear a problem - I didn't listen too much because I find the sound painful

birds
http://www.hydrogenaudio.org/forums/index....t=ST&f=16&t=821 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=821)
ABX 16/16 0 If she's singing "let us beeecome", there's a blip in the left channel on "us"

dogwhistle
http://www.hydrogenaudio.org/forums/index....t=ST&f=16&t=579 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=579)
I (unlike most other people) don't hear a problem - I didn't listen too much because I find the sound painful ;-)

drone_short
(url to first test?)
ABX 15/16 - sounds noisy during first sound - easy to hear (dropped on ABX due to lack of concentration!)

headache
http://www.hydrogenaudio.org/forums/index....t=ST&f=16&t=423 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=423)
didn't test

erhu
http://www.hydrogenaudio.org/forums/index....=ST&f=16&t=4687 (http://www.hydrogenaudio.org/forums/index.php?s=&act=ST&f=16&t=4687)
ABX 14/16 - blip in middle - easy (I almost didn't ABX - not sure what went wrong when I did?!?!)

liebestod
(url to first test?)
ABX 14/16 - difficult (for me) the background is rougher at points, but it's hidden by ambient noise (PC fan mainly) where I'm listening.

sophia2
http://www.hydrogenaudio.org/forums/index....t=ST&f=16&t=543 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=543)
I (unlike most other people) can't hear a problem - and I did try!

trumpets1
http://www.hydrogenaudio.org/forums/index....=ST&f=16&t=3594 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=3594)
ABX 13/16 - to my ears, the end of the trumpet is less "rough" in the encoded version, but it's very hard to hear

vangelis1
http://www.hydrogenaudio.org/forums/index....=ST&f=16&t=1107 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=1107)
ABX 15/16 - the bass line has a different "character" - it's probably transient smearing, as previously suggested.


Of these, awe32_20sec, birds, erhu and liebestod make me think that, on music I'm likely to encode, there's a very small (but greater than zero) chance of an artefact being encoded. Whether I ever notice it is a different matter!

Cheers,
David.


P.S. Dibrom - does this answer:
http://www.hydrogenaudio.org/forums/index....=ST&f=16&t=3594 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=3594)
still stand? No improvements on the horizon?

P.P.S. in case this thead is read by a newbie as an attack on aps/e/i, please remember that these settings are better than others out there for virtually every audio sample, easy or hard to encode.

P.P.P.S. I think "what samples is aps better than <whatever>" and "what are still problem samples for aps/e/i" should be prominently FAQed! I'm still finding people using FhG VBR! :-(
Title: samples where aps or ape has a problem
Post by: Pio2001 on 2003-03-25 19:50:46
Quote
badvilbel
http://www.audio-illumination.org/forums/i...=ST&f=16&t=1059 (http://www.audio-illumination.org/forums/index.php?act=ST&f=16&t=1059)
I (unlike most other people) don't hear a problem - I didn't listen too much because I find the sound painful

The problem is audible in headphones in a silent environment.
The reverberation after each noise is cut.
The "KRRRRRRsssssss", where "KRRRRRRR" is the noise, and "sssssss" it's decaying echo become
"KRRRRRRss---s-s--s", where - are silences.
Title: samples where aps or ape has a problem
Post by: guruboolez on 2003-03-25 20:11:12
--alt-preset VBR are suffering with harpsichord. Especially standard, on many harpsichord tracks. You can find a sample here :
http://membres.lycos.fr/guruboolez/ (http://membres.lycos.fr/guruboolez/)

Extreme is better, but not really hard to ABX. --insane is often near-transparency.




Interesting to note : I find Fhg codec bundled with CoolEdit [span style='font-size:8pt;line-height:100%'](VBR qual 100 HQ lowpass 20Khz) [/span]MUCH better than --alt-preset standard (3.90.2) for the same bitrate. And on a quick audio comparison, I find --ape a bit worse than the same Fhg encoding (but I need to ABX in order to confirm my impression with this sample).
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-26 10:58:27
guruboolez - thank you - you're right!


With aps I hear...

Fuge
ABX 8/8 - it's noisier behind the notes

Also from your website:

glass_short
ABX 7/8 - there's a "blip" about half way through. It's the same kind of problem as birds and erhu.


also... I know the song, but I've forgotten it, so can you tell me where "Jump" is from please? Artist and Album? Thanks!

btw, why do you .zip some ape files?


Cheers,
David.

P.S. can these samples from other places be added to the HA samples folder please? Specifically, awe32_20sec, and the above two, if it's OK with guruboolez. With sensible all lower case and no spaces filenames in .flac format?
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-26 10:59:18
Quote
The problem is audible in headphones in a silent environment.


That would be the problem then - no chance of that! Thanks for letting me know.
Title: samples where aps or ape has a problem
Post by: guruboolez on 2003-03-26 11:03:36
· Jump is a song from Van Halen (1984 album, but not sure).
· Funny, but I never notice any artifact with --alt-preset standard on the glass_short sample. I uploaded this sample in order to show the funny behaviour of mppenc at --standard preset (something like 260 kbps for a tonal sample)
· I can't put a direct link with a zip or rar file. There's an anti-leech system on Lycos pages.


EDIT : Yes, you're right, a 3.90.2 encoding has the same artifact than with erhu. No problem (or really low) with 3.94.a12. I never noticed it on a larger sample.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-26 15:57:15
Reading about the 3.94 alphas, I followed this suggestion from JohnV

http://www.hydrogenaudio.org/forums/index....16&t=6390&st=29 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=6390&st=29)


and added -Z to --alt-preset standard in 3.90.2. (I appologise that I'm catching up with this rather late!)

1. It solves the blip problems in erhu, birds, and glass.

2. I think it improves vangelis1 and drone (or else I'm not listening as carefully today - couldn't ABX - but I'm not convinced they're perfect).

3. Fugue ABX 8/9 (didn't notice I'd reached 7/8!) - it's still adding noise - about the same amount

4. It doesn't help awe32_20sec at all. For me the artefacts (the bass drum sound changes) aren't even subtle - I don't need to ABX - I can just get "X" correct without comparison. I've created an even more difficult sample (or obvious problem) by delaying one channel of awe32_20 by 40 samples.


aps -Z bitrate is significantly lower than ape on these samples, and yet the blip in erhu is still obvious with ape. This suggests that, for this sample/problem, ape doesn't deliver the "safety margin" it promisses, and is actually wasting bits without solving the problem. --alt-preset extreme -Z solves the problem, and I think it fixes Fugue too (compared to aps -Z). It doesn't fix awe32_20sec, but it improves it (compared to aps -Z).


Since glass_short wasn't even posted as a problem sample for aps, yet revealed this "blip" problem, which is present in two other (relatively normal) clips, isn't it sensible to suggest --alt-preset standard -Z as the "standard"? Or am I just being too picky?


Cheers,
David.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-27 10:10:10
At the risk of being a saddo who just bumps his own threads up... 

Is there an answer to this question? Or are the people who probably know (Dibrom, JohnV etc etc) more concerned with getting the next stable release right, than checking 3.90.2?

Cheers,
David.
Title: samples where aps or ape has a problem
Post by: KikeG on 2003-03-27 10:56:42
Quote
Interesting to note : I find Fhg codec bundled with CoolEdit [span style='font-size:8pt;line-height:100%'](VBR qual 100 HQ lowpass 20Khz) [/span]MUCH better than --alt-preset standard (3.90.2) for the same bitrate.

According to some tests I performed some time ago, CEP 2.0 Fhg codec, VBR max quality, was noticeabily worse than LAME aps on usual pre-echo test samples, but was better in trumpets1.wav. Still, LAME api was the best on this sample.
Title: samples where aps or ape has a problem
Post by: Dibrom on 2003-03-27 11:02:07
Quote
P.S. Dibrom - does this answer:
http://www.hydrogenaudio.org/forums/index....=ST&f=16&t=3594 (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=3594)
still stand? No improvements on the horizon?

There will be no further improvements by me if that's what you mean.  3.94 looks like a step in the right direction, but it sounds like there is a lot of tuning left to do, which is always the hardest part.  I don't know how things will turn out in the end, but my involvement with LAME has been over for awhile.
Title: samples where aps or ape has a problem
Post by: Dibrom on 2003-03-27 11:07:03
Quote
aps -Z bitrate is significantly lower than ape on these samples, and yet the blip in erhu is still obvious with ape. This suggests that, for this sample/problem, ape doesn't deliver the "safety margin" it promisses, and is actually wasting bits without solving the problem. --alt-preset extreme -Z solves the problem, and I think it fixes Fugue too (compared to aps -Z). It doesn't fix awe32_20sec, but it improves it (compared to aps -Z).

Originally, I had planned to modify --alt-preset extreme to use noise shaping 1 but stopped working on LAME before I got around to it.  At the time 3.90.2 was released, most of these samples weren't known about and so I believed that I'd finally fixed the artifacts related to noise shaping 2.  Most of the problems were solved, but a few remained which were discovered later in the samples you've pointed out.

So, yes, in place of --alt-preset extreme, one should probably use --alt-preset standard -Z instead.  FWIW, --alt-preset extreme never really did provide much of an improvement over --alt-preset standard, if any improvement at all.  I've never recommended that people use this over --alt-preset standard, and have instead recommened --alt-preset insane if they find --alt-preset standard to be insufficient for some reason.  I guess the main reason that I even included an --alt-preset extreme option is because I knew that people would tweak beyond --alt-preset standard even if they couldn't hear the difference anyway, so I figured it'd be best to give them a theoretical improvement rather then have them use some external switches which would negatively impact the --alt-preset behavior.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-27 12:25:41
Thank you.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-27 13:01:59
To settle aps -Z vs ape -Z vs api in my own mind, I returned to the harpsichord sample "Fugue", because I wasn't convinced by my results yesterday. However, I think I've confirmed them. For me:

aps = aps -Z : the notes are noisy
ape = ape -Z : it's still adding a little noise - just
api is transparent for me


I determined this using ff123's abc/hr comparator. The output was:

[span style='font-size:8pt;line-height:100%']
ABC/HR Version 0.9b, 30 August 2002
Testname: Fugue Test

1L = D:\audio\lame\apez\wav\Fugue.wav
2L = D:\audio\lame\api\wav\Fugue.wav
3L = D:\audio\lame\aps\wav\Fugue.wav
4L = D:\audio\lame\apsz\wav\Fugue.wav
5R = D:\audio\lame\ape\wav\Fugue.wav

---------------------------------------
General Comments:

---------------------------------------
1L File: D:\audio\lame\apez\wav\Fugue.wav
1L Rating: 2.5
1L Comment:
---------------------------------------
3L File: D:\audio\lame\aps\wav\Fugue.wav
3L Rating: 1.1
3L Comment:
---------------------------------------
4L File: D:\audio\lame\apsz\wav\Fugue.wav
4L Rating: 1.0
4L Comment:
---------------------------------------
5R File: D:\audio\lame\ape\wav\Fugue.wav
5R Rating: 2.4
5R Comment:
---------------------------------------
ABX Results:
Original vs D:\audio\lame\apez\wav\Fugue.wav
    8 out of 8, pval = 0.004
Original vs D:\audio\lame\api\wav\Fugue.wav
    4 out of 7, pval = 0.500
Original vs D:\audio\lame\aps\wav\Fugue.wav
    11 out of 12, pval = 0.003
Original vs D:\audio\lame\apsz\wav\Fugue.wav
    8 out of 8, pval = 0.004
Original vs D:\audio\lame\ape\wav\Fugue.wav
    7 out of 8, pval = 0.035
[/span]


(the ratings are relative - none of the files deserves lower than a 4.5 on the true MOS scale)


With awe32_20sec_2 the artefacts are more obvious, so I haven't ABXed today, but the differences are similar to above:

aps = aps -Z : not at all transparent (noise on first two bass drum hits)
ape = ape -Z : much better, but still there
api : even better still - but still very slight problem on first bass drum hit



On Fugue, the size of the difference in quality approximately corresponds to the size of the difference in bitrate.
On awe32_20sec_2, api is much larger than ape, but only a little better. ape is much better than aps, but only a little larger. (exagerated, but you get the point).


It seems there are (at least) two categories of artefact remaining:

one which occurs because of noise shaping 2 and can be removed by -Z

another due to "spiky" waveforms which mp3 just doesn't like, but can be minimised or removed by using the highest possible bitrate --alt-preset insane

maybe yet another due to pre-echo on some (soft?) transients with nspsytune, which can't be solved without another new psymodel.


It was interesting to hear your reason for creating --alt-preset extreme Dibrom. It seems that there is a practical use for the preset though: reducing the audibility of artefacts on the most difficult files, without hitting 320kbps. However, to quote your usual advice, if you really want to encode impossible files "as well as possible", use api or (better still) move to mpc.


The quality goes upwards from aps > aps -Z > ape -Z > api.

ape without -Z doesn't fit into this progression, since it's worse than aps -Z for some samples, but better for others.


Could the FAQ recomended command lines be changed to

--alt-preset insane
--alt-preset extreme -Z
--alt-preset standard -Z
--alt-preset standard

?

Honestly - that's my last question, then I'll drop it!


Cheers,
David.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-28 10:27:42
?
Title: samples where aps or ape has a problem
Post by: CiTay on 2003-03-28 11:40:17
Hmm, --aps -Z files aren't really that much bigger than --aps. Usually some 1 or 2 kbps increase on average. I also noticed faster encoding with -Z, reproducable. Example 1: With --aps, it goes down to ~4.6x speed and stays there. --aps -Z starts at 6x and levels off at ~5.8x speed. Example 2: --aps speed constantly increasing, reaching 6x towards the end. --aps -Z speed also increasing, but reaching 6.8x. LAME 3.90.2, P4 2.4. The size increase is negligible.

I want to know, is there a consensus about this quality ranking?

--alt-preset insane
--alt-preset extreme -Z
--alt-preset standard -Z
--alt-preset standard

Under these circumstances, i wonder if plain --aps should stay there at all?
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-03-31 11:16:24
?

Sorry to bump again, but it's kind of important, isn't it?

D.
Title: samples where aps or ape has a problem
Post by: DickD on 2003-03-31 17:14:55
I was searching for info on how -Z worked and found this old thread (http://www.hydrogenaudio.org/forums/index.php?act=ST&f=16&t=593&hl=scalefar,or,scalefactor,or,&quotscale+factor&quot,or,&quotz&quot&view=findpost&p=5392).

It seems to indicate that there are samples where using -Z to force use of that particular scalefactor can produce problems too, so the specific problem samples you tried, where -Z was no worse, might not be representative of the whole spectrum of music.

Of course, in the present thread, Dibrom has noted that certain samples (like those you tested) weren't known about then, so perhaps his opinion is now revised.

--alt-preset standard is well tested and lacks transparency only on rare cases. I don't think --alt-preset standard -Z has been tested anywhere near as much and shown to be OK, so I won't be using it, but I might try it if I notice a specific problem with APS (which won't be too often, now I mostly encode in Musepack mppenc --quality 5 --xlevel).
Title: samples where aps or ape has a problem
Post by: KikeG on 2003-04-01 10:05:49
IIRC, JohnV said that there's no problem in using -Z always, other than a bitrate increase.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-04-01 10:24:11
JohnV did say exactly that, but Dibrom said "and by specifying -Z you may end up degrading quality in cases as well."

I can't figure out if he had any specific for saying this, because it came in one of the (at the time) very frequent replies which essentially said "Look, don't worry about the switches which are in --alt-preset standard, because there are things which can't be accessed from the command line; and don't try to improve it by adding other switches, because it's already as good as it can get, and more importantly, you'll almost certainly make it worse by trying to 'tweak' it".

So maybe he had a very specific problem in mind, or maybe he was just trying to stop people messing with the --alt-presets.

Dibrom - please tell us!

Cheers,
David.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-04-03 15:52:36
?



With the many tests samples I've been trying, I am slowing coming to an even more contraversial conclusion... r3mix is often better than --aps!!!


Sorry - only joking! I should have tried this one on April 1.



Seriously though - I have found something which no-one here has ever said, probably because no one uses 128kbps CBR mp3: --alt-preset cbr 128 is often worse than -b 128 -h (i.e. the lame default). ap cbr 128 is probably better in the majority of cases (though I wouldn't bet my life on it), but there are many many samples where -b 128 -h is actually better than --alt-preset cbr 128.

This isn't a late April fool - try the samples listed in this thread for starters. Much of the time neither command line is transparent, so to some extent it depends on which artefacts you find most annoying; but there are some cases where lame default beats the "tuned" line hands down.


Just thought it was worth mentioning. I've already PMed ff123, who helped develop the command line behind --alt-preset cbr 128. Maybe the fact that it's worth trying other things (even other encoders) at 128kbps should be in the HA FAQ - and/or a subject for further lame tuning?


Anyway, what really interests me is the unanswered aps/e -Z issue - can adding -Z ever decrease quality? Please tell!

Cheers,
David.
Title: samples where aps or ape has a problem
Post by: JohnV on 2003-04-03 17:57:22
It has been said many times that Gpsycho has often for example better pre-echo control than plain vanilla nspsytune preset, so I don't know if that's anything new. Many times it has been said that the non-codelevel tweaked presets aren't necessarely always performing better than some other switches with a bunch of samples. The --alt-preset cbr 128 also suffers (although prolly not quite similarly) from the use of noise shaping type 2. Try the samples listed in this thread using --alt-preset cbr 128 -Z although this may not be ideal overall... And since GPsycho uses noise shaping type 1 by default, it performs very well with those samples which fail with ns-type2...

gpsycho plain vanilla -b128 -h is indeed not bad for 128kbps. But if you use abr, I think the advantage will turn more clearly to nspsytune considering overall quality aspects.

And no, in vbr coding I don't believe that using noise shaping 1 (-Z with APS/APE) will lead to worse quality, but it definitely leads to better quality in some cases. Lower quality with noise shaping 1 is definitely possible with lower bitrate cbr though.
Title: samples where aps or ape has a problem
Post by: Dibrom on 2003-04-03 18:17:01
Quote
So maybe he had a very specific problem in mind, or maybe he was just trying to stop people messing with the --alt-presets.

Dibrom - please tell us!

At the time I was creating the alt-presets for 3.90.2, I did come across 1 file where -Z actually did make quality worse.  I don't remember what this file was anymore though, and I only came across this issue once... so when I made that statement, it was with a specific issue in mind, though I don't know entirely how representative it was.  The point I was trying to make though was that with the lack of apparent samples where -Z improved things beyond the fixes I already implemented internally, it wasn't worth taking the chance.  Now that there have been many more files to pop up which cause problems without -Z, I'd realize the situation differently.
Title: samples where aps or ape has a problem
Post by: DickD on 2003-04-03 20:15:57
Just guessing (sorry!) but perhaps -Z could make things worse when the bitrate hits 320kbps (but could do with more) and it's forced to devote bits to satisfying -Z rather than minimising more obvious distortions? Still don't know which samples, but I guess some of the codec killers are especially high bitrate (e.g. artificial or noisy ones like badvilbel and fatboy?) and might suffer slightly. Still, -Z is only wasting a few kbps in those frames where APS acts differently, so could it really be this reason that quality might suffer?

Perhaps APS-Z should be tested more thoroughly? (Though I'm not sure I'd volunteer to ABX badvilbel for subtle changes!). It's sounding like it quite probably that it's a promising, though relatively minor improvement on an already excellent setting.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-04-04 10:53:19
Quote
It has been said many times that Gpsycho has often for example better pre-echo control than plain vanilla nspsytune preset, so I don't know if that's anything new. Many times it has been said that the non-codelevel tweaked presets aren't necessarely always performing better than some other switches with a bunch of samples. The --alt-preset cbr 128 also suffers (although prolly not quite similarly) from the use of noise shaping type 2. Try the samples listed in this thread using --alt-preset cbr 128 -Z although this may not be ideal overall... And since GPsycho uses noise shaping type 1 by default, it performs very well with those samples which fail with ns-type2...

Yes, I know the relative strengths and weaknesses of gpsycho vs nspsytune are very very old news - I remember discussions in the r3mix forum!

Where --alt-preset cbr 128 is worse than -h -b 128, I think it's almost entirely due to nspsytune, since -Z does almost nothing to help. (On a quick check, it sounds like it does something on awe32, but not on the others). And, as you say, adding -Z to ap cbr 128 would probably cause problems elsewhere.

I know you're doing some tweaking, and introducing new presets in the current lame alphas - and also (obviously) that ABR beats CBR - but while the current FAQ recommendations still stand, can the FAQ include alternatives at 128kbps? It might be honest to suggest that FhG is worth a try. Not on a page two links down, but actually there in the list of recomended settings.

Cheers,
David.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-04-04 11:11:25
Quote
The point I was trying to make though was that with the lack of apparent samples where -Z improved things beyond the fixes I already implemented internally, it wasn't worth taking the chance.  Now that there have been many more files to pop up which cause problems without -Z, I'd realize the situation differently.

So, you're basically saying that, on the current evidence, we should use -Z?


You and JohnV have removed any serious quality worries, but there was also the issue of bloat. I've read that -Z may increase the bitrate. Maybe I don't have the right test samples, but this is barely happening here - it's a 1kbps increase.

Can someone who has a CD which produces a low bitrate using aps try encoding it again with aps -Z please?


DickD - yes! Will someone else listen to aps -Z please? I'm a good listener, but I'm in a noisy environment and I can't hear above 16kHz - so other people really need to check what I'm saying! It doesn't have to be badvilbel - there's plenty of other fun samples - or just grab a CD at random.

Cheers,
David.
Title: samples where aps or ape has a problem
Post by: Gabriel on 2003-04-04 11:20:08
David, would you try adding --athtype 0 to preset 128?

This could be a workaround against the source of the problem.
My idea is:
Gpsycho estimates tonality up to cwlimit (around 8kHz by default). Upper freqs are all considered to be noise sounds and not tonal sounds. As noise is generating more masking, upper freqs have more masking than lower freqs.
If I'm not wrong, Nspsytune is computing tonality up to the higher relevant part (sfb20?), so higher freqs have less masking than with Gpsycho.

Athtype 0 would increase the masking for the higher freqs. This is obviously not the right solution. Imo the right thing to do would be to have non linear spreading for Nspsytune.
Title: samples where aps or ape has a problem
Post by: Wombat on 2003-04-04 11:27:44
I use aps -Z for a long time now. I don´t encode much these days.
When i only used aps i stumbled across samples that are bad from time
to time. Most annoying is the Liebestod sample - it is that ugly without
-Z i don´t want to risk any other song to get the same problems. Even if
there would be a possibility another sample may get "a bit" worse. (haven´t found one)

I never stumbled over a really annoying artifact with MY music since i use
aps -Z. I bet with plain aps i would have more samples to offer.

How much the real bitrate differences are, i can´t tell.
Title: samples where aps or ape has a problem
Post by: JohnV on 2003-04-04 12:43:50
Quote
You and JohnV have removed any serious quality worries, but there was also the issue of bloat. I've read that -Z may increase the bitrate. Maybe I don't have the right test samples, but this is barely happening here - it's a 1kbps increase.

Can someone who has a CD which produces a low bitrate using aps try encoding it again with aps -Z please?


DickD - yes! Will someone else listen to aps -Z please? I'm a good listener, but I'm in a noisy environment and I can't hear above 16kHz - so other people really need to check what I'm saying! It doesn't have to be badvilbel - there's plenty of other fun samples - or just grab a CD at random.

Yes, using aps/ape -Z increases bitrate but not always. Also one have to understand that there are only some positions on a track where noise-shaping 1 and noise-shaping 2 can sound different, the positions where one or both noise shaping types use scalefactor_scale.

Noise Shaping 1 (APS/APE -Z):
When Lame notices that all scalefactors are even numbered, it halves the values thus saving some bits in coding. This is quality wise "lossless" and is no different outcome than using no scalefac_scale at all (except for the bit saving).

So when Noise Shaping type 1 is used, only lossless bitrate saving happens in certain places. (You can see with EncSpot how many percent of the track is encoded using scalefac_scale).


Noise Shaping 2:
Noise Shaping 2 adds another trick for bitrate saving. When the encoder decides to use scalefac_scale (not necessarely in same places as with NS1), the scalefactor values are doubled. Since scalefactors are used to control the reduction of quantization stepsizes (which control how much noise per SFB is present), the dynamics is larger for the stepsize adjustment. It can go more closer to the "edge" of allowed noise, which of course saves bits.

With Noise Shaping 2, Lame should use scalefac_scale only when it's "safe". Obviously this is not always succeeding, and NS2 scalefac_scale can introduce even quite bad audible distortion sometimes, especially when using vbr-old nspsytune. The masking threshold/allowed noise is not perfect because of the imperfect psychoacoustics, and sometimes it fails when it has the chance to go more closer to the edge. I'd think with better psychoacoustics NS2 would work ok.

Now because of code level tweaking, APS/APE use less often Noise Shaping 2 than without code-level tweaking, but it's still not enough to be totally "safe".

IMO NS2, because it's not safe, is not the right type for VBR coding. But CBR acts differently and low bitrate CBR can gain quality from the bitrate savings given by NS2 scalefac_scaling.
Title: samples where aps or ape has a problem
Post by: CiTay on 2003-04-04 15:16:28
Okay, i changed the List of recommended LAME settings (http://www.hydrogenaudio.org/forums/index.php?s=&act=ST&f=15&t=203&st=0). What about the "fast" switches though?
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-04-04 16:25:38
Quote
David, would you try adding --athtype 0 to preset 128?

Gabriel, it doesn't seem to help. Actually, I don't think it helps at all. Sorry!


I'll list the samples where I think --alt-preset cbr 128 is surprisingly bad, as it might help someone to listen or tune...

awe32_20sec - obvious noise
vangelis1 - start of notes replaced by noise
testsignal2 - softening of drum hits
youcantdothat - the intro is wobbley (though the vocal is much better than gpsycho could ever manage!)
fatboy and spahm  - really - they're arguably worse than -h -b 128

The first two are obvious, the next two are subtle, and the last two are debatable. I know I shouldn't be encoding any of them at 128kbps - but anyway, I hope this information helps!


Cheers,
David.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-04-04 16:31:42
JohnV - thanks for that long explanation. It would explain (kind of) what I've seen by inverse mix pasting: occasional places where --aps adds MUCH more noise than --APS -Z, though (to my ears) in most of these places, it "gets away with it". We're catching the few where it doesn't.

CiTay - thanks. I hope that meets with everyone's agreement.

I haven't listened to the fast presets - I'll try to find time to try next week. Whereas the 128 stuff is blindingly obvious, the aps -Z stuff does require ABX with some serious concentration - if someone else can do it, I'd be very happy!

Cheers,
David.
Title: samples where aps or ape has a problem
Post by: ff123 on 2003-04-04 16:50:47
2BDecided,

Thanks for that list of samples.

I'll probably update my 128 link to show that the preset's weaknesses, and also make it clear that no one codec can be the best for all files.

ff123
Title: samples where aps or ape has a problem
Post by: user on 2003-04-11 14:02:33
--alt-preset fast standard / extreme ?

dev0:

" Think about adding -Z to the fast presets too. It should result in a quality gain there too.

dev0 "



Correct ?
Title: samples where aps or ape has a problem
Post by: Frank Klemm on 2003-04-11 15:41:30
Quote
Yes, using aps -Z increases bitrate but not always. Also one have to understand that there are only some positions on a track where noise-shaping 1 and noise-shaping 2 can sound different, the positions where one or both noise shaping types use scalefactor_scale.

Noise Shaping 1 (APS -Z):
When Lame notices that all scalefactors are even numbered, it halves the values thus saving some bits in coding. This is quality wise "lossless" and is no different outcome than using no scalefac_scale at all (except for the bit saving).

So when Noise Shaping type 1 is used, only lossless bitrate saving happens in certain places. (You can see with EncSpot how many percent of the track is encoded using scalefac_scale).


Noise Shaping 2:
Noise Shaping 2 adds another trick for bitrate saving. When the encoder decides to use scalefac_scale (not necessarely in same places as with NS1), the scalefactor values are doubled. Since scalefactors are used to control the reduction of quantization stepsizes (which control how much noise per SFB is present), the dynamics is larger for the stepsize adjustment. It can go more closer to the "edge" of allowed noise, which of course saves bits.

With Noise Shaping 2, Lame should use scalefac_scale only when it's "safe". Obviously this is not always succeeding, and NS2 scalefac_scale can introduce even quite bad audible distortion sometimes, especially when using vbr-old nspsytune. The masking threshold/allowed noise is not perfect because of the imperfect psychoacoustics, and sometimes it fails when it has the chance to go more closer to the edge. I'd think with better psychoacoustics NS2 would work ok.

Now because of code level tweaking, APS/APE use less often Noise Shaping 2 than without code-level tweaking, but it's still not enough to be totally "safe".

IMO NS2, because it's not safe, is not the right type for VBR coding. But CBR acts differently and low bitrate CBR can gain quality from the bitrate savings given by NS2 scalefac_scaling.

Using some simple math you find out the following equation:

optimal_Stepsize = 17.312... dB / Number_of_spectral_lines

6 dB steps are optimal for 3 bundeled spectral lines.
3 dB steps are optimal for 6 bundeled spectral lines.
2 dB steps are optimal for 9 bundeled spectral lines.
Title: samples where aps or ape has a problem
Post by: 2Bdecided on 2003-04-11 16:30:35
Quote
--alt-preset fast standard / extreme ?
dev0:

" Think about adding -Z to the fast presets too. It should result in a quality gain there too.

I wasn't completely ignoring the question (it's already been asked in this thread) - I was just avoiding it long enough for someone else to do the listening  Busy week this week. Remind me next Tuesday - or someone else can try - please?

Cheers,
David.