18/32 - there's a harshness in the left channel around the 8.5 mark, which I had originally mistaken for ground hum, which I felt I could possibly distinguish in character between 16hpt and 24. I started pretty good at 5/6 but I felt like I could not hold on to the difference.
~26,000 views... and still a mystery. ;>
Anyway, you wanted to know what I heard in David's dithered 16-bit version...
If one takes any two different audio files and mixes them together, one has a combination, such as a vocal and backing track now in one file. If one then takes one of the two, inverts it, and mixes it with the combination, as in the above paragraph, one is left with the original of the other file -- almost.In the first mixing, each resulting sample is the sum of the corresponding samples from the two inputs. A quantization error occurs in every case where the sum of the two exceeds the precision the format can carry. This will occur even when working in 32 bit float.
First, I truncated (no dither) the file to only 8 bits. Then I performed a null test, comparing it to the 24 bit version. As Ethan and others have observed, mostly noise and definitely no music there.BUT, when I took this 'noise' (the result of the null test) and combined it with the truncated 8 bit version, it really helped to 'restore' the music. So, the conclusion would be that we can't simply listen to a null test difference and say it's only noise and not music related information.
Greetings, found your forum recently, so here's my first post! Wanted to share another set of files that might be useful for listening tests. The source material is a 'raw' unprocessed master recording downsampled from 96kHz. Uploaded the files here:Digital audio resolution test filesBelow you can see a quick ABX result I got using my laptop and a pair of Beyerdynamic DT250 headphones.The second set of files are from an old master tape, comparing 24 bit versus 12 bit versus 320kbps mp3.
Quote from: AndyH-ha on 22 January, 2009, 04:12:30 PMI know I can convert properly; possible audible differences with other conversions to 16 bit are of no value. Tests based on them on very suspect. I understand most anyone can do a proper conversion, given the necessary software, but a fuller specification of the particular process employed is desirable.What exactly do you need to know apart from the dither used? Please let me know. While I understand that this is slightly controversial, we have to remember that most professional audio is done in 24 bit today, probably for good reason. So we could at least suspect an audible difference. But it's a good idea to download only the source file to save download time.Quote from: AndyH-ha on 22 January, 2009, 04:12:30 PMBlue printing on a black background is extremely difficult to read.Oh, I'm sorry, looked fine on my screen, but fixed it now! Please reload the page. Thanks for pointing that out.MartinQuote from: 2Bdecided on 22 January, 2009, 07:45:53 AMIt would be helpful if Martin Kantola could describe the differences he heard, where in the file he heard them, and most importantly can verify that his laptop plays back 16-bit and 24-bit digital audio correctly.While the hardware of my laptop is 24bit/192kHz capable, the specs are not exactly impressive:Will get back to the differences I heard, have to try a 16 bit padded to 24 bits to make sure it works as it should. Martin
I know I can convert properly; possible audible differences with other conversions to 16 bit are of no value. Tests based on them on very suspect. I understand most anyone can do a proper conversion, given the necessary software, but a fuller specification of the particular process employed is desirable.
Blue printing on a black background is extremely difficult to read.
It would be helpful if Martin Kantola could describe the differences he heard, where in the file he heard them, and most importantly can verify that his laptop plays back 16-bit and 24-bit digital audio correctly.
I would sincerily hope that *nobody* would try to do *anything* definitiive with these files. Based on my evaluaton of the 24/96 version...
Martin suggests this isn't the point, because hearing doesn't work like that, and then gives two (IMO unconvincing) examples...I don't know how your ears work, but to my ears, the 24-bit file sounds fine, the 8-bit file sound horribly noisy, and the "difference" / "null" file sounds exactly like the noise in the 8-bit file, but without the music. I don't hear any magic - there's "music", "music + noise", and "noise". In my mind, if you remove the "noise" from the "music + noise" I'd expect it to sound like "music". It doesn't surprise me at all.
I don't know if this is what we have here. lossyWAV thinks the dither might be audible anyway, so how loud is Martin playing these files?
Martin: can you ABX the "null" file vs digital silence? At the same listening loudness that you can ABX 24-bits vs 16-bits?
I would sincerily hope that *nobody* would try to do *anything* definitiive with these files. Based on my evaluaton of the 24/96 version, here's not enough energy > 20 Khz (or even 5 Khz!) to be meaningful, and the dynamic range is only about 60 dB. If you want to convince yourself that 12 KHz sampling and 12 bits are pretty good, be my guest!
What I tried to show was that we clearly removed more than "just noise" when truncating, and so the removed bits must contain signal-related information. Adding any other uncorrelated noise (with the same spectrum) to the truncated file would not do the trick.
1 = signal2 = signal + noise_A3 = 2 - noise_A = (signal + noise_A) - noise_A = signal = 1
what is the noise floor of the tape noise?
foo_abx 1.3.1 reportfoobar2000 v0.9.4.22009/02/09 16:29:47File A: D:\audio\digital audio resolution test files\96k24b.wavFile B: D:\audio\digital audio resolution test files\mp3-48k320kbps.wav16:29:47 : Test started.16:31:04 : 01/01 50.0%16:31:25 : 02/02 25.0%16:31:39 : 03/03 12.5%16:31:50 : 04/04 6.3%16:32:12 : 05/05 3.1%16:32:20 : 06/06 1.6%16:32:30 : 07/07 0.8%16:32:43 : 08/08 0.4%16:32:44 : Test finished. ---------- Total: 8/8 (0.4%)
Total: 8/8 (0.4%)Easy. The "T" of "I'm travelling light" is changed by the mp3 encoding.
This is the first time I listened to it. I agree it's a nice recording in many ways. It would have to be butchered by noise reduction to go onto a CD though. Play that as-is on the radio today and the hiss would be dragged up to be louder than the music.
I don't know what mp3 encoder + settings you used (and hissy recordings are a challenge to mp3 in general) but I bet it can be encoded better than that.
P.S. EDIT: That "24/96" recording looks like it was copied in the analogue domain from a CD. There's a null at 22kHz, a little crap (completely unrelated to the music) a little above it, and then nothing but noise, tens of dB down, above that.
You believe there's something magical...
I don't dispute the overall point you're trying to make - noise_A might be related to the signal. In fact, it demonstrably is (if you know what to look for, you can create waveforms where this fact is clearly visible).
But what you've done doesn't prove it. We need to look deeper than that.
Here's an interesting question (for the 16-bit version at least): Does any similar (but completely uncorrelated) noise make it sound worse, or is it only dithering+truncation that makes it sound worse? In other words, is noise_A a special "bad-case", or not?
Could this whole situation be simply from Martin's poor-quality audio card causing some kind of non-linear distortion that makes these results actually audible when normally they are not?
Quote from: 2Bdecided on 09 February, 2009, 11:21:48 AMHere's an interesting question (for the 16-bit version at least): Does any similar (but completely uncorrelated) noise make it sound worse, or is it only dithering+truncation that makes it sound worse? In other words, is noise_A a special "bad-case", or not?Not sure I follow you 100% here, please help me understand, but you make the assumption that noise_A is only... noise?
As far as audible on a good system, I would go as far as claiming that any full time mastering engineer not able to hear the difference between the 24 bit source and the 16 bit on his own setup should probably get another job...