samples where aps or ape has a problem Options

[2Bdecided]

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.

[2Bdecided]

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:


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



(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.