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Topic: 'tonal Purity'? 'musicality'? (Read 10172 times) previous topic - next topic
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'tonal Purity'? 'musicality'?

Reply #25 –
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I posted samples and ABX results about this in the past, you should be able to find them in the archive.

whhooo... Any hints on what to search for? Both "ABX" and "MPC" would generate a lot of hits. (If you still remember anything of what you wrote...)

Bleh. I couldn't find them in the archive myself

'tonal Purity'? 'musicality'?

Reply #26 –
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It's not only in non-transient sections. The interesting question is also what happens in the transient sections

Yes, but I was talking what people like Tord and Chris Johnson mean. They claim that you can either have good transient accuracy or good "tonal purity", but not both. But bad transient handling in no way makes a transient more "tonally pure", bad transient handling makes transients sound like s*it.
Tord and Chris Johnson obviously only refered to non-transient part of the signal, because there's no way anybody can say pre-echo makes something sound "tonally pure" in any sense..
Juha Laaksonheimo

'tonal Purity'? 'musicality'?

Reply #27 –
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Yes, but I was talking what people like Tord and Chris Johnson mean. They claim that you can either have good transient accuracy or good "tonal purity", but not both. But bad transient handling in no way makes a transient more "tonally pure", bad transient handling makes transients sound like s*it.
Tord and Chris Johnson obviously only refered to non-transient part of the signal, because there's no way anybody can say pre-echo makes something sound "tonally pure" in any sense..

Why not?

'tonal Purity'? 'musicality'?

Reply #28 –
Because for one, Pre-echo doesn't sound "pure", and it doesn't sound "tonal". 

Pre-echo usually sounds noisy, unstable (a bit warbly kind of), sometimes static-like, or it just gives the attacks a generally "gritty" and kind of dirty sound.

It doesn't in any way fit into any sort of definition I could imagine for "tonal purity".

The whole concept of tonal purity and this nonsense that Tord and Chris Johnson have been pushing is based simply on a misunderstanding of psychoacoustics and of lossy audio encoders which uses these principles.

As JohnV said, Tord came up with this theory to try to downplay Blade's weaknesses.  You can see this in the same manner in which he talks about joint stereo, etc.

And you can see this in Chris Johnsons tests because due to the methodology he uses, you can see that he completely misses the necessary colleration between psychoacoustic principles and how these affect the audibility of lost information (through selective degredation).  Instead, he tries to draw a flawed correlation between the visibility of "flaws" in low resolution spectrograms and the audibility of lost information.

See the problem here?  He's not testing aural quality, he's testing visual quality, and he somehow comes to the conclusion that whichever codec looks the best in a certain situation must feature the most "tonal purity". 

Yeah.. ok. 

'tonal Purity'? 'musicality'?

Reply #29 –
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Why not?

Why Not?? 
Because pre- or post-echo is audible distortion. There's nothing "tonally pure" in distorted transients, on the contrary. I can't think of that distorted transient with excess audible noise would be "tonally pure", that's the last thing I'd describe it.. 
Juha Laaksonheimo

'tonal Purity'? 'musicality'?

Reply #30 –
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Because for one, Pre-echo doesn't sound "pure", and it doesn't sound "tonal".  

Pre-echo usually sounds noisy, unstable (a bit warbly kind of), sometimes static-like, or it just gives the attacks a generally "gritty" and kind of dirty sound.

It doesn't in any way fit into any sort of definition I could imagine for "tonal purity".

I more or less disagree. Even in a wide spectrum impulse sound (i.e. some kind cymbal) you brain will still be able to associate a certain tone or frequency with this sound. If this changes after encoding, I'd define it as a 'tonal impurity'  (a better word is much appreciated)

Edit: Uh, misunderstanding. OF COURSE preecho doesn't sound tonally pure. But even an impulse sound can have some tonality, which is what I was trying to explain.

'tonal Purity'? 'musicality'?

Reply #31 –
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Edit: Uh, misunderstanding. OF COURSE preecho doesn't sound tonally pure. But even an impulse sound can have some tonality, which is what I was trying to explain.

  Yeah, I wasn't trying to say that impulses don't have tonality.  Rather, only that pre-echo is not "tonally pure".

'tonal Purity'? 'musicality'?

Reply #32 –
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Edit: Uh, misunderstanding. OF COURSE preecho doesn't sound tonally pure. But even an impulse sound can have some tonality, which is what I was trying to explain.

Yes, impulse sound can have tonality, but when it's affected by pre-echo, it's obviously not as tonal anymore for a listeners, since pre-echo-noise is now making it sound distorted and less tonal, maybe even totally different sounding. 
Juha Laaksonheimo

'tonal Purity'? 'musicality'?

Reply #33 –
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I think you misinterpreted what I said. MPC does excellent on transients. I have never heard any problems with it's 'tonal purity' (gah) either in normal music.

But in the few samples (like, 2 or 3) where I was able to ABX an MPC --standard (with a previous version) clip (out of the hundreds I tried), it was on a transient and it sounded like a tonal problem.

Comparing this to a transform codec is silly. MPC does much better there on every sample. The clips where MPC failed were clips where the transform coders had much much worse problems.

I know, mpc is much better than most any codecs out there qualitywise  But what I was trying to say is that it turns out that the places where mpc has troubles (although it usually overcomes them  ) is not as different from trouble spots for transform codecs after all

'tonal Purity'? 'musicality'?

Reply #35 –
Yes attacks processing does have an impact on tone purities. There is a few official tests clips that specifically tailored for this. The clips Glockenspiel, gspi35_1 & gspi25_2 and also mc_sich2 is used to detect distortion of tone components when switched to short-block.. Of course, castanets is a bad test sample for tone purity during transients.

Short Blocks generally have bad tone separations compared to long block.
From fft analysis of audio signals, tone isolation decreases as the length of the fft decreases. 

For AAC, when switched to 8 short blocks, the pre-echo noise is no longer caused by all 8 short blocks but only 1 of the short blocks.. As a results the remaining short blocks could have very tonal components which could be wrongly "squashed".. Maintaining tonal purity during transients is a very delicate tasks.

To be more accurate, maintaining tone purity in region very near to the actual attack is a concern here..


wkw