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16 bit vs 24 bit, any samples that work?
AndyH-ha
post Feb 15 2007, 11:52
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Yes, it is easy to create test tones that demonstrate a difference. That was my opening statement. The question is, is there any music?

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SirChristof
post Feb 15 2007, 20:17
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The vast majority of all music most of us have access to is in 16-bit.

The real question to me is not if the difference is audible in music during critical listening, but whether we can get a sufficient sample library of 24-bit tracks in order to appreciate such a difference. Since we do not have this (or at least, I do not), we are reduced to using synthetic test tones to demonstrate the difference in the meantime.

And as for "is there music?" I would most certainly say yes, if you consider all genres that people currently count as "music". That may just be 1 "test tone" I posted, but I could easily make it part of, say, a PC-Based techno song which people actually enjoy listening to, and at low levels they would easily be able to ABX my track between a 24 and 16 bit version.

This post has been edited by SirChristof: Feb 15 2007, 20:18
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SometimesWarrior
post Feb 15 2007, 21:41
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These articles on ff123's website may be of interest to you:

The MAD Challenge
Analysis of Ethan Winer's Bit-Depth Listening Test

The first link compares 16-bit and 24-bit decodes of an MP3. I just glanced at the article, so I'm not sure if the MP3 is provided, but if it's not linked in the article it probably is on ff123's samples page. (Look for a link from the home page.)

The Bit-Depth Listening Test provides a dynamic 24-bit audio recording and several bit-truncated versions, and it's pretty well put-together. Click through the links in the article and you'll get to the samples themselves.

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greynol
post Feb 15 2007, 21:48
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QUOTE (SirChristof @ Feb 15 2007, 00:40) *
You need fairly high output levels to do this, but since the file contains no peaks or anything that would resemble "loud", you wont risk damaging your hearing or equipment so long as no other "computer sounds" play during testing.

QUOTE (SirChristof @ Feb 15 2007, 11:17) *
That may just be 1 "test tone" I posted, but I could easily make it part of, say, a PC-Based techno song which people actually enjoy listening to, and at low levels they would easily be able to ABX my track between a 24 and 16 bit version.
rolleyes.gif

Well, which is it?


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SirChristof
post Feb 15 2007, 22:02
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Greynol,

What I meant to imply by "at low levels", was parts of the song where the overall level of the track itself is very quiet. High gain playback would still be necessary, as I mentioned prior. Thank you for helping me to clarify.

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Kees de Visser
post Feb 15 2007, 22:15
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QUOTE (SirChristof @ Feb 15 2007, 09:40) *
You need fairly high output levels to do this, but since the file contains no peaks or anything that would resemble "loud", you wont risk damaging your hearing or equipment so long as no other "computer sounds" play during testing.
Any noise (even 24-bit dither) can be made audible with enough monitoring gain. That's not really a fair test. It can be handy though to "zoom in" to details that would normally be inaudible, but are still good to know they exist. Just like a printer checking a printout with a magnifying glass.
Quite a few mastering engineers claim audible differences between dither flavours at normal playback levels. I'm pretty sure these claims have not been confirmed by double-blind testing though.
Best thing to do is find a mastering engineer who is willing to share a sample with a clear 24/16 bit difference. I'll try to contact a few. Please do so too if you have the possibility.
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krabapple
post Feb 16 2007, 06:07
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QUOTE (SirChristof @ Feb 15 2007, 14:17) *
The vast majority of all music most of us have access to is in 16-bit.


What about taking a DVD-Audio release (generally they're 24 bit) and rerecording the two-channel analog output digitally, at 24 bits?

I've got a couple of dozen DVD-As, several of which I've re-digitized in just that fashion via my M-Audio 2496 card so i could make flac files from them (after converting to 16-bit -- but I still have the 24-bit 'masters').


(Alternately those who have the DVD-A ripping software could use that).
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AndyH-ha
post Feb 16 2007, 08:17
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As far as I can see, the ff123 page does not provide the 24 bit file, just various 16 bit, and lesser bit depth, versions. It isn't addressing the question of this thread, it is just about various way of presenting material resampled to lower bit depths.
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Kees de Visser
post Feb 16 2007, 11:01
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At least one of the engineers I've asked seems prepared to provide some samples where the difference between 24 and 16 bit should be "easily" audible. I'm waiting for more samples to come.
Would it be an idea to set up a public listening test for this ? I've never done that, so any help and suggestions would be welcome.
-How long should a sample be in order to be valid ? (my guess: 30 sec. max., see HA TOS #9)
-What is the preferred sample rate ? (my guess: 44.1 kHz with 48 optional)
-What kind of music is preferred (my guess: any should do)
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muaddib
post Feb 16 2007, 11:54
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IMO it is better to keep samples much shorter: 10-15 sec. That way it will be easier for people to concentrate just on the part that is important. To conduct listening test you can simply follow Roberto's document about conducting listening test.
Maybe 48 kHz would be better to avoid issues if some listener use those soundcards that have crappy sampling rate convertors. But then on those soundcards it might also be impossible to hear the difference anyhow.
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2Bdecided
post Feb 16 2007, 12:07
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There are a few 24/96 and 24/44.1 files here:
http://www.pcabx.com/technical/reference/index.htm

McDougalsMen24bit_48kHz.flac is here:
http://ff123.net/samples.html

Cheers,
David.
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AndyH-ha
post Feb 16 2007, 12:22
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Setting aside for the moment whether this donated tone, 24-bit-ABX, might ever be considered music, my first listening based impression was that I can tell no difference between the 24 bit and a dithered 16 bit version. A run of 14 trials with WinABX said otherwise, however. I guessed correctly 12 of those times, for a guessing probability of 0.6%.

Whatever I based my guesses on was below the level of my conscious awareness. I doubt that it would ever occur to me that there might be a difference if I did not know there was supposed to be.

I turn my headphone amplifier up quite far rather often. I need to listen to samples that are down 60 to 70 dB, as part of the restoration process I do (mostly from LPs). I know from painful experience that forgetting to turn the dial back down is very unpleasant when switching to "normal" level music.

In order to even hear this test tone, I need the volume setting to be much higher than I ever use it in my daily noise sample testing. In order to hear it well enough to do the ABX test, I had the volume set on maximum. I don't know what sound pressure level is produced by this. Your equipment might provide significantly greater amplification; your hearing might be significantly more sensitive. However, I am reasonably sure that no human could listen to music at anything approaching that setting on my system unless the entire composition was at a similar input level as this test tone.

That, of course, would be too contrived to accept. To be reasonable, the file would then need to be normalized to "normal" music levels, where the differences between 24 bit and 16 bit would probably be much less. After normalizing it to -16dB (which is loud at a volume control setting below my normal listening level), and resampling a copy to 16 bits, a run of 14 trials produced 13.something% probability of guessing for me. I'm not sure how to interpret that.

Again, laying aside the question "is it music?", is there any disagreement that a piece that contained this tone, along with parts at more normal levels (thus precluding the volume control being set at an extreme level) would need to be listened to under extraordinary conditions for such low level parts to be heard at all? In real music, such low level sounds might occur at a fade out, but probably no one ever hears them.

Also, music is not always at a constant level. For this sample to be useful in the ABX tests, it needs to be part of something, as emphasized by Axon. Adding higher level music might change the ABX test results considerably -- unless one insists that really extended durations of such a low level tone are a worthwhile contribution to some composition. Who knows what musical genius might wrought? Tunes for the Sensory Deprivation Vat

So, let me restate part of the hypothesis that led to this thread. I don't remember just what was written in what other thread, but something was being discussed with one or more proponents of "24 bit is better" and that prompted me to start this thread (I've made similar challenges in other forums. This test tone is the first offering with which anyone has ever responded).

I acknowledge that there are real differences between 16 bit and 24 bit, but is there any actual music where that difference can be distinguished under real world conditions? While most of them might not hang around this neighborhood, there are more than a few people who proclaim that 24 bit recordings (as finished products) are so much better than CDs. I rather doubt it is because said recordings contain parts at -110dB. I want someone to produce even one sample of some 24 bit music that can be successfully ABXed against a properly resampled 16 bit version of same. I'm not saying it doesn't exist but I want to hear it for myself.



An addendum to the comments about higher sample rates by SebastianG, which comments I afraid didn't make much sense to me: I generated two samples of 32 bit silence, one at 48kHz (keeping with the parameters of the tone under consideration here) and one at 96kHz. I resampled both to 16 bit with the dither I normally use.

At maximum headphone volume, the 48kHz sample sounds the same as silence; I hear nothing (from the added noise shaped dither). However, the 96kHz sample is definitely audible. Perhaps this is a defect of the soundcard when running at 96kHz. CoolEdit's Statistics say the 96kHz file has both lower peak and lower RMS levels.

Repeating the 96kHz silence sample with a noise shaping preset labeled for 96kHz, the perceived loudness is decreased (but still audible), but the measured levels are higher than for even the 48kHz dithered sample.



I don't know what a "public listening test" might involve, but I want to be able to resample the 24 bits to 16 bits myself. I suspect it is possible to bias the results towards 24 bits by doing a less than splendid job of resampling.
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Kees de Visser
post Feb 16 2007, 15:10
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QUOTE (AndyH-ha @ Feb 16 2007, 12:22) *
I don't know what a "public listening test" might involve, but I want to be able to resample the 24 bits to 16 bits myself. I suspect it is possible to bias the results towards 24 bits by doing a less than splendid job of resampling.
My idea was to ask a few Majors in the audio industry for samples at 24 and 16 bit. Preferably at 44.1 kHz and with the same dither flavour they use for their cd-releases. These samples will be made publicly availble for testing purposes, allowing anyone to try to hear a difference.
That doesn't stop you from making your own 16-bit version of the 24-bit sample if you think you can do a better job.
IMO this test essentially boils down to comparing various dither versions. It seems that there are no double blind test results publicly available. This could be an opportunity for HA. It's recommended that the listening test is performed at normal (healthy) listening levels with real life music samples, preferably from commercial releases to be representative (this might be open for discussion).
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Kees de Visser
post Feb 19 2007, 23:00
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An ABX test to compare 16 and 24 bit dithered audio (44.1 kHz) won't be easy (although at least one of the ppl I've asked for samples thinks it is).
It will probaby require quite some time and motivation. Would HA be a good place for such a test, since 320 kbps is already considered transparent by a majority of the members ?
Just to get an idea, who of you would like to (seriously) participate in such a test ?
QUOTE (AndyH-ha @ Feb 16 2007, 12:22) *
I don't know what a "public listening test" might involve, but I want to be able to resample the 24 bits to 16 bits myself.
I suspect it is possible to bias the results towards 24 bits by doing a less than splendid job of resampling.
Out of curiosity, what kind of dither would you use ?
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AndyH-ha
post Feb 20 2007, 00:30
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I believe the resampling is more important than the dither. I can use any dither possible with CoolEdit, and I'm open to suggestions for test purposes. Mainly I use shaped triangular to a depth of 0.5, CoolEdit's noise shaping curve C1. I've also used triangular, dither depth 0.7, C3 quite a bit.

Neither of these is audible by itself. I guess that doesn't necessarily mean they don't have audible effects on the music but nothing I've noticed. In fact, it is quite difficult to find any music where dithering or not dithering makes any audible difference when going from 24 bit (32 float) to 16 bit.

Test tones are easy but most music has enough self dither, from the microphone preamp if nothing else, that adding more, or not adding any, is irrelevant. I've also asked several forums, this one included, I believe, for any 24 bit music sample anyone thinks will exhibit a difference. I've always done this when the thread was in some manner stressing the importance of dither or some aspect thereof, at least by some posters. No one has ever offered any actual music.
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MLXXX
post Feb 25 2008, 16:52
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Hi everyone.

A year has passed since the previous post in this thread.

Some of the posts have referred to listening for the noise floor. That to me would be a means of testing but would not go to the heart of the matter.

If the superiority of leaving the final mix at 24-bits is not evident in soft passages when listening with a normal amount of gain, one must wonder whether it is worthwhile at all for the final product to have more than a 16-bit sampling depth.

So I ask, is it still a moot point whether a 24-bit musical extract has been successfully ABX tested as sounding better than a 16-bit dithered version?

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AndyH-ha
post Feb 26 2008, 00:52
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"sounding better" is a subjective evaluation. The question here is whether or not it is possible to tell any difference what-so-ever. Just as one can not prove there is no Easter Bunny, no one can supply evidence that there is no 24 bit music recording that can be differentiated from a 16 bit version of same. So we have to approach the problem from the other direction: can anyone supply a 24 bit recording that people can tell from a 16 bit version of same simply by listening to them (in an ABX presentation, of course)
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MLXXX
post Feb 26 2008, 15:25
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I am new to ABXing but I think that for playing 24-bit material it may be wise to use ABX software where the audio driver in use is known, as some drivers ignore the extra bits. I have just installed a full version of foobar2000 and I see it offers ABX testing, and selection of the audio driver.

When I get some spare time I will compare some selections of 24-bit material (e.g. some amateur 24/96 recordings) with 16-bit derived versions. I see that foobar2000 can even be used to convert files so as to create 16-bit versions (with or without dither).

And if I find I can reliably hear a difference I will report back, and upload (or identify) the test file. (In the past I have felt quite confident I could detect a more liquid sound with greater than 16-bits, but the proof of the pudding will be in the ABX testing.)
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.halverhahn
post Feb 26 2008, 17:28
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Even it is comparing apples with oranges:

Do you expect to hear differences between 16 bit and 24 bit at normal listenig conditions, when you can't seperate 192kbit CBR-MP3 vs. Original CD-16bit/44kHz rip?!

Any lossy Encoder does much more "harm" to the sound, then 24bit audio is noiseshaped & dithered to 16bit audio.


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digital
post Feb 27 2008, 10:37
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Wow: Nov 2nd 2006 to Feb 27th, 2008Ö and still waiting for A/B/X-able material (!)

Cool thread nonetheless - Iím just hoping that someone will be able to source two lossless .wav files in the aforementioned bitrates. I'll offer to host em' free for a couple of years if someone can dig them up in the first place.

Andrew D.
www.cdnav.com
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knutinh
post Feb 27 2008, 10:43
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Since DVD-A can now be ripped, having 24/96 stereo material is not an issue.

The success of 16 vs 12 bit tests should tell us a lot about the prospect of 24 vs 16 being detactable, I cant understand why those arent properly discussed.

The line between test-signal and music is blurred when you search for killer-samples. Lets just say something like "any snip of sound less than 30s long that is normalised to 0dB FS and still comfortable to listen to?"

Caution
Is it concievable that the 24bit version might sound different but worse than dithered 16bits in some PCs if 24 bits was truncated to 16 bits by soundcard/OS?

-k
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Kees de Visser
post Feb 27 2008, 11:51
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QUOTE (knutinh @ Feb 27 2008, 10:43) *
Caution
Is it concievable that the 24bit version might sound different but worse than dithered 16bits in some PCs if 24 bits was truncated to 16 bits by soundcard/OS?
Good point. Any playback chain that is not capable of processing 24 bits correctly is not suitable for this kind of testing.
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GeSomeone
post Feb 27 2008, 12:10
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I remember remarks (don't know where) that indicate that "a slow fade out" could be one of the things you might want to try. In effect bits are gradually taken away during a fade out.

The reason we see 24 bits anyway is probably the idea (as said before) that it is useful during recording/editing in the studios and so why not leave it without reduction (regardless if a difference can be heard at home). But, sorry, that has nothing to do with proof. laugh.gif


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knutinh
post Feb 27 2008, 15:00
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I think that the difference between 12 bits and 16 bits is a lot easier to prove, both due to technical and perceptual issues.

If one tries 12 vs 16 first, and cannot proove the difference, then continuing with 16 vs 24 is a waste of time (either due to your equipment, ears, room, content... ).

-k
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MLXXX
post Feb 27 2008, 16:59
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QUOTE (knutinh @ Feb 28 2008, 00:00) *
I think that the difference between 12 bits and 16 bits is a lot easier to prove, both due to technical and perceptual issues.

If one tries 12 vs 16 first, and cannot proove the difference, then continuing with 16 vs 24 is a waste of time (either due to your equipment, ears, room, content... ).

-k

True, however 12 bits is very easy to pick simply by listening for the background noise, at a normal listening level, so perhaps a more reasonable initial challenge would be to try with 14 bits.

For example, there is a well presented set of samples at this webpage of the PC ABX Web Site. Here are my results from this evening, mainly involving 12 bits vs 16 bits:-
Sample 2.2.6 (Triangle 44.1KHz 12 bits) is much noisier than sample 2.2.1 (Triangle 44.1KHz 16 bits).

The poor quality of 12 bits is even more stark with the gliding tone samples. Artefacts are clearly audible in sample 1.1.7 (Tone sweep 44.1KhZ, 12 bit, undithered) but sample 1.1.2 (Tone sweep 44.1KHz, 16 bit, dithered) is of good quality.

However, even that 16 bit sample can be heard to have slight deficiencies if you listen to the last section of it at high gain, and compare it with sample 1.1.1 (Tone sweep 44.1KHz, 24 bit). To satisfy hydrogenaudio protocol I confirmed the samples sounded different with ABX testing, but I had no hesitation identifying which sample was which, just through noise levels.

Turning to the piano extracts provided on the webpage, the recording is very noisy and the difference between the 44.1Khz 12-bit sample (2.1.6) and the 16-bit sample (2.1.2) is not particularly obvious [to my ears]. I find it disappointing that such a poor sample was used.

If I start with an ordinary 16-bit file of quiet music, drop the volume level by 24dB, save the file, open the file and raise the volume level by 24dB I think this should get rid of about 4 least significant bits, leaving 12 bits. I performed this procedure tonight and the noise introduced was apparent, even at a normal listening level.

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