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Topic: Great killer sample, easy to ABX on most codecs (Read 8092 times) previous topic - next topic
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Re: Great killer sample, easy to ABX on most codecs

Reply #50
Let's take MP3 for example.
Original lossless file doesn't have lots of useful stuff above 16 kHz.
LAME will see this and it will decide to cut it to save space.
Let's add lossless and MP3 file to foobar.
It sounds dull. We can use DSP to enhance higher frequencies. Lossless will sound great because it preserves whole frequency range.
MP3 will sound terrible because it doesn't actually have any higher frequencies to enhance.
If you applied DSP effects to lossless file and then converted to MP3 situation would be different.

I am just saying that if you want to do fair test, do not use any DSP effects while playing.
Different models of headphones, earbuds or speakers in various rooms all have their own unique frequency responses and distortion levels. Just like DSPs, these all affect the audio chain after decoding the file/stream. Therefore, in the example of the quote above, MP3 that sounds terrible by the boost from the equalizer would still sound terrible when that boost is occurred by a headphone.

What makes changes occurred by DSPs unacceptable while those caused by using different equipment acceptable in lossy codec tests?

Also, tests with files that were processed before encoding do not reflect most real-life use cases. No music downloading/streaming services that I know of provide custom processed lossy streams. Consumers decode the stream and process that.

Re: Great killer sample, easy to ABX on most codecs

Reply #51
Yes, they do affect the audio chain after decoding ...
... but encoder does not expect any processing after decoding.
It is tuned/optimized for original unprocessed file.
Encoder has no idea what you are going to do with your files later.

With lossless files you have lots of bits to work with, with lossy ~192 kbit/s you don't.
Any kind of processing will make it much easier to ABX.
This is the reason why we always use lossless files when encoding lossy files.

Using DSPs for listening is okay, but for ABXing is not.
You want to be as neutral as possible.

Sure, some people are using DSPs for lossy files and it sounds good to them because:
1. They are playing music, not doing ABX test
2. They don't have original lossless file to compare it with
gold plated toslink fan

Re: Great killer sample, easy to ABX on most codecs

Reply #52
It's headphone frequency response equalization filtering. It is tuned based on an accurate digital recording of the headphones' own frequency response curve, and is designed to produce a flat response after the correction is applied. To say that this sort of correction is invalid, is the same thing as saying that testing with any headphones which do not already have a perfectly flat response is also invalid.

Re: Great killer sample, easy to ABX on most codecs

Reply #53
It doesn't matter what kind of DSP you are using - the only important thing is that it does processing.
With lossy files it is working with 192000 (you get the idea, no need to nitpick) bits of information.
With lossless files it is working with at least 1411200 bits of information.
DSPs might be transparent, but that doesn't change the fact that chance of audible artifacts is increased.

Using the same logic as you guys, I can grab 128 kbit/s MP3 file, convert it to Opus and cry online because it is not transparent.
Of course it is not transparent because it was already processed by another encoder that reduced the available bits of information.

Like I said above, using DSP for listening is good, but for ABX, big no-no.
gold plated toslink fan

Re: Great killer sample, easy to ABX on most codecs

Reply #54
You can say the same damn thing about headphones making the audio not transparent and that tests should only be performed with the best studio monitors in a recording studio.

Re: Great killer sample, easy to ABX on most codecs

Reply #55
Using the same logic as you guys, I can grab 128 kbit/s MP3 file, convert it to Opus and cry online because it is not transparent.
Of course it is not transparent because it was already processed by another encoder that reduced the available bits of information.
What...?

Okay, that's enough. An equalizer and a lossy encoder are totally different types of processing altogether and you just equated those.

-What does the frequency response of a linear time invariant system tell you about that system?
-What should you do with the frequency domain transfer functions of each linear time invariant system connected in series in order to acquire an accurate frequency response of the entire connected system?
-How do digital equalizers change the frequency level of a signal? Can you explain the difference between FIR and IIR filters?
-What is room correction and why is it absolutely necessary for accurate audio reproduction with speakers unless you are in an anechoic chamber?
-Why is just blindly compensating for the measurements of a headphone not a good way of obtaining a perfect target curve for you even when the measurement of that headphone is accurate?

If you don't know the answer to the questions above, you are talking out of your depth. If you know the answer to those questions and don't tell me a plausible reason why DSPs shouldn't be used in ABX tests when difference between gears and rooms are larger but acceptable, you are trolling and I am not going to take your response seriously.

So, please answer the question: Both DSPs and headphones, earbuds, speakers, and rooms etc. change the frequency response of the signal. Therefore, it can be said that both the former and the latter "process" the signal. Why is processing by the former unacceptable, but that of the latter acceptable in ABX testing? You have to explain the difference between "processing" by the former and latter.

Re: Great killer sample, easy to ABX on most codecs

Reply #56
You can say the same damn thing about headphones making the audio not transparent and that tests should only be performed with the best studio monitors in a recording studio.

I've not read most of this thread because it's totally off the rails now. However, I agree with this statement and would add "with qualified listeners".

This is a great example of how ABX testing is only valid for the listener and the files tested. You can't really extrapolate from the results. I mean, for god sake, this test file is just boring, generic dance music. I could find 100 examples of this "filtered white noise over kick drum" technique.


Re: Great killer sample, easy to ABX on most codecs

Reply #58
I've finally decided to do an ABX test with Wavpack -b450hh and Apple 320k  CVBR to see if I can hear the artifacts.
WavPack is obvious (unacceptable for my setup). Apple is more subtle and I think I woudn't hear it in normal listening situation (maybe on very loud volume but I'm not sure).

I have to point out that I'm not a trained listener (at least until now :D).

Sound: Lenovo Thinkpad E595 - standard output (Volume 90%)
Headphones: Audio Technica ATH-M40X

WavPack -b450hh

foo_abx 2.0.6c report
foobar2000 v1.4.8
2021-07-19 11:29:42

File A: CodecTest 16-bit.flac
SHA1: fa044d2f4662f4689707666fe971d64d4882093b
File B: CodecTest 16-bit.wv
SHA1: e55b262a8685148d7d4230ca7095683fd1a2479b

Output:
DS : Primary Sound Driver
Crossfading: NO

11:29:42 : Test started.
11:32:44 : 01/01
11:33:06 : 02/02
11:33:32 : 03/03
11:33:45 : 04/04
11:33:56 : 05/05
11:34:02 : 06/06
11:34:14 : 07/07
11:34:22 : 08/08
11:34:27 : 09/09
11:34:31 : 10/10
11:34:31 : Test finished.

 ----------
Total: 10/10
p-value: 0.001 (0.1%)

Apple 320k CVBR

foo_abx 2.0.6c report
foobar2000 v1.4.8
2021-07-19 11:39:16

File A: CodecTest 16-bit.flac
SHA1: fa044d2f4662f4689707666fe971d64d4882093b
File B: CodecTest 16-bit.m4a
SHA1: 5c568899f4d3dec7767c77ad45734ff0b305b86e

Output:
DS : Primary Sound Driver
Crossfading: NO

11:39:16 : Test started.
11:41:42 : 01/01
11:41:57 : 02/02
11:42:15 : 03/03
11:42:31 : 04/04
11:42:47 : 05/05
11:43:28 : 06/06
11:43:44 : 07/07
11:43:53 : 08/08
11:44:23 : 09/09
11:44:46 : 10/10
11:44:46 : Test finished.

 ----------
Total: 10/10
p-value: 0.001 (0.1%)

Re: Great killer sample, easy to ABX on most codecs

Reply #59
I see. That is imortant for me to know. Hard to make a difference even on abx.
Thanks a lot.

You can use static noise shaping value like -s0.5 (-b450hhs0.5)
This will shift noise to the higher freq.

Do you think that is safe to use -s0.5 in general?

Yes. Especially at high bitrate.
wavpack hybrid 256k -hx4

Re: Great killer sample, easy to ABX on most codecs

Reply #60

You can use static noise shaping value like -s0.5 (-b450hhs0.5)
This will shift noise to the higher freq.

Do you think that is safe to use -s0.5 in general?

Yes. Especially at high bitrate.
[/quote]

Excellent! Thanks. I'll play with s0.5 to see the differecies.

Out of curiosity I've tried to ABX Aften AC3 @320k but I couldn't do it.
I always thought that AC3 is kind of lower quality but this sample surprised me.

Re: Great killer sample, easy to ABX on most codecs

Reply #61
@shadowking
I've tried the -s0.5 switch and it really helps.
450hhs0.5 is definitely better than 450hh.

Re: Great killer sample, easy to ABX on most codecs

Reply #62
Out of curiosity I've tried to ABX Aften AC3 @320k but I couldn't do it.
I always thought that AC3 is kind of lower quality but this sample surprised me.
Considering that MDCT-based codecs seem to be having a tougher time (than the subbands ones) with this sample in particular, plus you not having done any additional tweakening to AC3's settings, this seems to be really worth mentioning.
Listen to the music, not the media it's on.
Wavpack -hb4.3

Re: Great killer sample, easy to ABX on most codecs

Reply #63
At that point, it may even be worth investigating hybrid lossy/lossless codecs, or even lower bitrate ADPCM codecs. Those usually expose degradation as noise, which depending, may not be as noticeable, or may be a less annoying form of distortion. You pick your poison, hissing that's way less than tape hiss, versus smearing artifacts, or other things.

I mean, ADPCM is a preferred A2DP codec, even. AptX and its relatives are a subband ADPCM codec.

Re: Great killer sample, easy to ABX on most codecs

Reply #64
Out of curiosity I've tried to ABX Aften AC3 @320k but I couldn't do it.
I always thought that AC3 is kind of lower quality but this sample surprised me.
Considering that MDCT-based codecs seem to be having a tougher time (than the subbands ones) with this sample in particular, plus you not having done any additional tweakening to AC3's settings, this seems to be really worth mentioning.

Especially considering is still very popular for movie audio.

Re: Great killer sample, easy to ABX on most codecs

Reply #65
At that point, it may even be worth investigating hybrid lossy/lossless codecs, or even lower bitrate ADPCM codecs. Those usually expose degradation as noise, which depending, may not be as noticeable, or may be a less annoying form of distortion. You pick your poison, hissing that's way less than tape hiss, versus smearing artifacts, or other things.

I mean, ADPCM is a preferred A2DP codec, even. AptX and its relatives are a subband ADPCM codec.

My experience with wavpack so far is very positive. Small, very fine hiss could be heard very rarely on critical samples,
but on this sample is further distorted into  more aggressive noise (it is still minor issue but it stands out - very fine hiss is more blended into music, at least as I percieve it)
Reminds me of shaking wired fence. I don't know how to descibe it more accurately.

Re: Great killer sample, easy to ABX on most codecs

Reply #66
Out of curiosity I've tried to ABX Aften AC3 @320k but I couldn't do it.
I always thought that AC3 is kind of lower quality but this sample surprised me.
Interesting. Tried ffmpeg's AC3 (more recent)?
High Voltage socket-nose-avatar

Re: Great killer sample, easy to ABX on most codecs

Reply #67
Out of curiosity I've tried to ABX Aften AC3 @320k but I couldn't do it.
I always thought that AC3 is kind of lower quality but this sample surprised me.
Interesting. Tried ffmpeg's AC3 (more recent)?

Yes. Just few days ago I've tried Shanaencoder v5.04 which is basically frontend for ffmpeg. Same thing. I would say same quality (based on this sample).
Maybe someone with better ears and/or equipment could say something more about Aften/ffmpeg AC3 behavior on this sample, but considering how Apple AAC sounds, AC3 is better (to my ears).

I also tried Helix mp3 @320k CBR and V150 VBR (~230k). Also high quality. I didn'tbtry to ABX it but on normal listening throug headphones I coudn't make a difference.
I wonder why is not so popular as LAME is. Not to mention its extremly fast encoding speed.

Tried Lossy FLAC @ Economic 410k and couldn't ABX it.
Good alternative to wavpack, but i have very limited experience with Lossy Flac.
I'll definitely put some free time to LossyFlac testing.
It seems interesting.


Re: Great killer sample, easy to ABX on most codecs

Reply #69
Yes, I did it the way the OP did.
lame3995o -Q1.7 --lowpass 17

Re: Great killer sample, easy to ABX on most codecs

Reply #70
@synclagz:

I also wonder why helix isn't that popular. It has proved to be quite robust when it comes to problematic samples.
Guess one point is that HF behavior beyond 16 kHz isn't great with helix. Though this probably isn't a real issue to many people.
The idea of a 20...20000 Hz frequency range just is too popular though the range beyond 16 kHz can hardly be heard by most people older than 30. Also musical contents in the HF range is often of little importance for many pieces of music.

Other than good reasons it's chance to a large extent which controls popularity.

Also problems like this one are interesting but have no practical meaning to most people. These problems are often very artificial. Important are problems related to real instruments. Harpsichord music can be a problem to various encoders. But for people who are not much into this music it hardly applies. Very tonal regions in music can be a problem too when using low or moderate bitrate. Same goes for transients in music. But with a bitrate of roughly 200 kbps on avg. you're safe with many formats and encoders when listening to 'normal' music in a 'normal' listening environment. There are exceptions, but they are rare. Even 128 kbps is very good for many formats and encoders. Even old mp3 is good here when using Lame or Helix. Sure there are better formats like aac or opus, and using 200 kbps or more isn't an issue with today's storage possibilities.

LossyFLAC is a good thing for bitrates in the range you used. I did use lossyFLAC for a long time. However the popular lossy codecs are totally satisfying to me at a much lower bitrate.
lame3995o -Q1.7 --lowpass 17

Re: Great killer sample, easy to ABX on most codecs

Reply #71
@halb27
Hi,

Thanks for clarifying things about Helix. :)
Today I noticed that helix mp3 encoded files have higher track peak value than vorbis or aac (foobar replay gain scanner).
So I'm getting track peak value for some songs in 1.30 - 1.45 range which indicate potential clipping but I can't hear it.
Are these higher peak values of any concern?

As for LossyFlac, I can't find a critical sample to test it. IIRC, you said long time ago that herding_calls doesn't sound right. Do you still have that sample by any chance? I can't find it.

I also noteced that switching off noise shaping (-s o) drastically increases encoding speed of LossyFlac.
Using Standard or High preset sound excellent even without noise shaping.
Do you think that it can be safely switched off for higher presets (400-500k range) without sacrificing quality?


Re: Great killer sample, easy to ABX on most codecs

Reply #72
I wouldn't care about peak values >1 in encoded material. In case you do you can lower input in advance with a tool like Audacity or similar.

You can download herding_call from my webspace: http://horst-albrecht.de/misc/herding_calls.flac

I wouldn't switch off lossyFLAC noise shaping.
lame3995o -Q1.7 --lowpass 17

Re: Great killer sample, easy to ABX on most codecs

Reply #73
I wouldn't care about peak values >1 in encoded material. In case you do you can lower input in advance with a tool like Audacity or similar.

You can download herding_call from my webspace: http://horst-albrecht.de/misc/herding_calls.flac

I wouldn't switch off lossyFLAC noise shaping.

Thank you for herding_calls and clarifying things. :)
I'll test LossyFlac to see how this sample sounds on different settings.

Re: Great killer sample, easy to ABX on most codecs

Reply #74
EQ everything.  I was told by audiophiles to never do it. I have suffered for
years as a result. The treble is out of control in many speakers and headphones.
It may be a good thing for mixing but not for listening. I think the senheiser sound is
not a bad starting point maybe a bit veiled. I try to duplicate it with EQ. The same EQ
preset works for both speakers and phones.  I leave the low end , dial down mid bass and mid-top end.
it helps with samples like these and also your hearing. You can listen louder with less chances of damage.

 
wavpack hybrid 256k -hx4

 
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