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16 bit vs 24 bit, any samples that work?
AndyH-ha
post Nov 3 2006, 03:19
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There are real differences between 16 bit and 24 bit files, just as there are real differences between uncompressed and mp3. As with the differences between wav and mp3, 16 bit vs 24 bit is often difficult to identify by listening.

Test signals are one thing, but has anyone found any 24 bit music recording that can be successfully identified via ABX testing against a properly resample to 16 bit version of same?
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cabbagerat
post Mar 3 2008, 16:17
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QUOTE (MLXXX @ Mar 3 2008, 06:35) *
QUOTE (cabbagerat @ Mar 4 2008, 00:23) *

With proper dither, there will be no artifacts other than noise.

If I am not mistaken, that is the question we are trying to resolve, whether the arte[/i]facts that can be heard (even with optimal dither) when test tones are used, set at very low levels, and listened to at a high gain setting, can also be heard by the human ear at realistic listening levels, with music.

Well, if that's the question, then to my mind it's already been resolved for 24bit -> 16bit conversions. Consider our 24bit music samples x[n] and dither signal d[n]. Now, we define e[n], which is the difference between the x[n] and quantize_to_16bits(x[n] + d[n]). Ok? Now, optimal dither would do two things:

1) Make e[n] and x[n] completely uncorrelated, and
2) Reduce the total power of e[n], while still achieving (1), or
3) Reduce the audibility of e[n] while still achieving (1).

From what I understand, for the case of quantization from 24bits (or 32 bits) to 16 bits, the formulation of the jitter signal d[n] to achieve (1) is well understood. The formulation of d[n] to achieve (2) and (3) is a little bit less well understood, but still can be very well approximation with common processes. What (1) means is that there is no distortion at all caused by the quantization process - only the addition of noise.

I think the whole 24 bit/16 bit thing boils down to the hypothesis:
Consumer music and movie soundtracks have sufficient dynamic range, that when listened to at "normal" levels, the noise introduced by optimal dithering and quantizing to 16 bits is audible.
In my opinion, this hypothesis is yet to be resolved conclusively for real world music and movie soundtracks. This has been demonstrated to be true for some classes of test signals.

This post has been edited by cabbagerat: Mar 3 2008, 16:18


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MLXXX
post Mar 4 2008, 16:25
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QUOTE (cabbagerat @ Mar 4 2008, 01:17) *
~ Well, if that's the question, then to my mind it's already been resolved for 24bit -> 16bit conversions. Consider our 24bit music samples x[n] and dither signal d[n]. Now, we define e[n], which is the difference between the x[n] and quantize_to_16bits(x[n] + d[n]). Ok? ~


Er, yes, "ok" after several re-readings!

Expressed non-mathematically, I can understand how a high frequency dither can be used to supplement missing intensity level detail for lower frequency signals; and to mask the remaining low levels of quantisation error.

I've decided that my chances of being able to hear artefacts when playing back real life music in a 16-bit format derived from a higher bit depth source, and using a quiet dither, are likely to be confined to the artefact of the dither noise itself.

Using a 300Hz test tone at -60dB, my AVRs when fed a 24-bit PCM bitstream, play the tone with some background noise, and a small edge of distortion. Substituting a 16-bit PCM undithered version of the test tone, the distortion becomes quite pronounced. Adding triangular dither, the pronounced distortion disappears but dither noise is quite apparent. [It is certainly the lesser of the two evils.]

Minus 60 decibels is a very low signal compared with 0dB, a ratio of 1:1000 in fact. And the dither noise is quite a bit quieter than that.

The noise level of my microphone preamplifier/mixer competes with the dither noise if the gain is set to avoid clipping at 0dB. So to make a recording of music (e.g. a pianoforte) where the dither noise was appreciably greater than other noises, and to include in the recording a passage within a few decibels of 0dB, I would need a new preamplifier. [Fortunately the microphones have very low noise.]

If I were to succeed in this exercise [ABX tested, and dither method acceptable], what would I have proven? Simply that at very high (many would say artificially high) listening levels, dither noise can be audible when listening to a high signal to noise ratio 24-bit stereo recording of music, reduced to 16 bits.

That is not the narrow result I had assumed. I had assumed that some other artefacts might be audible. But I gather that other artefacts will almost certainly be neutralised, or sufficiently masked, by the dither noise.

This post has been edited by MLXXX: Mar 4 2008, 16:34
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Posts in this topic
- AndyH-ha   16 bit vs 24 bit   Nov 3 2006, 03:19
- - Mike Giacomelli   I'd imagine ABX would be possible if you found...   Nov 3 2006, 03:25
- - pdq   I recall a test here some years back to try to see...   Nov 3 2006, 05:33
- - Aetmos   If the clip is properly dithered, this doesn't...   Nov 3 2006, 06:22
- - cabbagerat   QUOTE (Aetmos @ Nov 2 2006, 21:22) If the...   Nov 3 2006, 07:31
|- - Aetmos   QUOTE Welcome to HA. I see this is your first post...   Nov 3 2006, 16:17
- - AndyH-ha   I agree that a good sample, if it exist in music, ...   Nov 3 2006, 09:36
- - cabbagerat   QUOTE (AndyH-ha @ Nov 3 2006, 00:36)...   Nov 3 2006, 16:25
- - Axon   I suppose it's quite easy to construct a track...   Nov 3 2006, 17:48
- - Axon   Also, how contrived can the listening environment ...   Nov 3 2006, 18:03
- - AndyH-ha   The question isn't whether or not it is possib...   Nov 3 2006, 20:18
- - Axon   Well.. how much dynamic range can you coax out of ...   Nov 3 2006, 20:38
- - AndyH-ha   I'm sorry, that went over my head. What is the...   Nov 3 2006, 21:21
- - outscape   haha nothing.. see 24 bits is purist technology. i...   Nov 3 2006, 22:23
- - greynol   I'd wager that in order to distinguish the dif...   Nov 3 2006, 22:41
- - Axon   OSHA's recommendations for 120db is that it sh...   Nov 4 2006, 01:11
- - AndyH-ha   But are you talking about real music or, effective...   Nov 4 2006, 01:56
- - Axon   My point is that you don't need a "test s...   Nov 4 2006, 02:21
- - AndyH-ha   OK, you need more than the dynamic range of 16 bit...   Nov 4 2006, 04:09
- - Iain   I think the best volume for the test would be ...   Nov 12 2006, 17:14
- - AndyH-ha   Without cryogenic cooling the intrinsic noise of e...   Nov 12 2006, 19:23
- - SebastianG   I think it's a good idea to mention the import...   Nov 13 2006, 13:30
- - AndyH-ha   QUOTE I think it's a good idea to mention the ...   Nov 14 2006, 03:43
|- - SebastianG   QUOTE (AndyH-ha @ Nov 14 2006, 03:43...   Nov 15 2006, 14:16
- - SirChristof   If you have decent equipment and a quiet environme...   Feb 15 2007, 09:40
|- - Kees de Visser   QUOTE (SirChristof @ Feb 15 2007, 09:40) ...   Feb 15 2007, 22:15
- - AndyH-ha   Yes, it is easy to create test tones that demonstr...   Feb 15 2007, 11:52
- - SirChristof   The vast majority of all music most of us have acc...   Feb 15 2007, 20:17
|- - krabapple   QUOTE (SirChristof @ Feb 15 2007, 14:17) ...   Feb 16 2007, 06:07
- - SometimesWarrior   These articles on ff123's website may be of in...   Feb 15 2007, 21:41
- - greynol   QUOTE (SirChristof @ Feb 15 2007, 00:40) ...   Feb 15 2007, 21:48
- - SirChristof   Greynol, What I meant to imply by "at low le...   Feb 15 2007, 22:02
- - AndyH-ha   As far as I can see, the ff123 page does not provi...   Feb 16 2007, 08:17
|- - Kees de Visser   At least one of the engineers I've asked seems...   Feb 16 2007, 11:01
- - muaddib   IMO it is better to keep samples much shorter: 10-...   Feb 16 2007, 11:54
- - 2Bdecided   There are a few 24/96 and 24/44.1 files here: http...   Feb 16 2007, 12:07
- - AndyH-ha   Setting aside for the moment whether this donated ...   Feb 16 2007, 12:22
|- - Kees de Visser   QUOTE (AndyH-ha @ Feb 16 2007, 12:22...   Feb 16 2007, 15:10
|- - Kees de Visser   An ABX test to compare 16 and 24 bit dithered audi...   Feb 19 2007, 23:00
- - AndyH-ha   I believe the resampling is more important than th...   Feb 20 2007, 00:30
- - MLXXX   Hi everyone. A year has passed since the previous...   Feb 25 2008, 16:52
- - AndyH-ha   "sounding better" is a subjective evalua...   Feb 26 2008, 00:52
- - MLXXX   I am new to ABXing but I think that for playing 24...   Feb 26 2008, 15:25
- - .halverhahn   Even it is comparing apples with oranges: Do you ...   Feb 26 2008, 17:28
- - digital   Wow: Nov 2nd 2006 to Feb 27th, 2008 and still wai...   Feb 27 2008, 10:37
- - knutinh   Since DVD-A can now be ripped, having 24/96 stereo...   Feb 27 2008, 10:43
|- - Kees de Visser   QUOTE (knutinh @ Feb 27 2008, 10:43) Caut...   Feb 27 2008, 11:51
|- - bubbleguuum   QUOTE (Kees de Visser @ Feb 27 2008, 11:5...   Feb 27 2008, 20:32
|- - MLXXX   QUOTE (volvme+ @ Feb 28 2008, 04:27)...   Feb 28 2008, 10:11
- - GeSomeone   I remember remarks (don't know where) that ind...   Feb 27 2008, 12:10
- - knutinh   I think that the difference between 12 bits and 16...   Feb 27 2008, 15:00
|- - MLXXX   QUOTE (knutinh @ Feb 28 2008, 00:00) I th...   Feb 27 2008, 16:59
- - volvme+   Sorry for interrupting your conversation, but I do...   Feb 27 2008, 19:27
- - MLXXX   AndyH, perhaps you might be kind enough to answer ...   Mar 3 2008, 07:27
- - cabbagerat   QUOTE (MLXXX @ Mar 2 2008, 22:27) Being a...   Mar 3 2008, 10:43
|- - MLXXX   QUOTE (cabbagerat @ Mar 3 2008, 19:43) ~ ...   Mar 3 2008, 13:48
|- - Soap   QUOTE (MLXXX @ Mar 3 2008, 07:48) When I ...   Mar 3 2008, 14:11
|- - MLXXX   Thanks, Soap. I should have been more precise. Wh...   Mar 3 2008, 15:06
- - SebastianG   Hi! I'd like to remind you that there...   Mar 3 2008, 11:02
- - AndyH-ha   I know this isn't the only time I raised the t...   Mar 3 2008, 12:03
- - cabbagerat   QUOTE (SebastianG @ Mar 3 2008, 02:02) I...   Mar 3 2008, 13:25
- - cabbagerat   QUOTE (MLXXX @ Mar 3 2008, 04:48) If I am...   Mar 3 2008, 15:23
|- - MLXXX   QUOTE (cabbagerat @ Mar 4 2008, 00:23) Wi...   Mar 3 2008, 15:35
- - cabbagerat   QUOTE (MLXXX @ Mar 3 2008, 06:35) QUOTE (...   Mar 3 2008, 16:17
|- - MLXXX   QUOTE (cabbagerat @ Mar 4 2008, 01:17) ~ ...   Mar 4 2008, 16:25
- - AndyH-ha   I generally issue this type of challenge when some...   Mar 4 2008, 19:45
- - MLXXX   I've a added a 24-bit 48KHz original, and 16-b...   Mar 10 2008, 16:00
- - Pio2001   Hello, In september, I did an ABX between a 96 kHz...   Nov 26 2008, 22:25
|- - Canar   QUOTE (Pio2001 @ Nov 26 2008, 13:25) Voxe...   Nov 27 2008, 00:27
||- - Dynamic   QUOTE (Canar @ Nov 27 2008, 00:27) QUOTE ...   Nov 27 2008, 05:27
|- - Kees de Visser   QUOTE (Pio2001 @ Nov 26 2008, 22:25) I go...   Nov 27 2008, 10:32
- - Pio2001   Thank you for the precisions about dither. This is...   Nov 27 2008, 19:48
- - Canar   I fully recognize that, and want to thank you agai...   Nov 27 2008, 21:18
- - solive   QUOTE (AndyH-ha @ Nov 2 2006, 18:19)...   Jan 5 2009, 01:28
- - greynol   http://www.hydrogenaudio.org/forums/index....showt...   Jan 5 2009, 01:38
|- - Martin Kantola   Greetings, found your forum recently, so here...   Jan 21 2009, 22:04
|- - Kees de Visser   QUOTE (Martin Kantola @ Jan 21 2009, 22:0...   Jan 22 2009, 07:37
- - 2Bdecided   I can't ABX it. I agree it's a perfectly g...   Jan 22 2009, 13:45
- - AndyH-ha   I m going to see if I can borrow a fast connectio...   Jan 22 2009, 22:12
|- - Martin Kantola   QUOTE (AndyH-ha @ Jan 22 2009, 16:12...   Jan 23 2009, 05:01
|- - Ron Jones   QUOTE (Martin Kantola @ Jan 22 2009, 20:0...   Jan 23 2009, 05:58
||- - Martin Kantola   QUOTE (Ron Jones @ Jan 22 2009, 23:58) As...   Jan 23 2009, 06:23
|- - 2Bdecided   QUOTE (Martin Kantola @ Jan 23 2009, 04:0...   Jan 23 2009, 11:47
|- - Martin Kantola   QUOTE (2Bdecided @ Jan 23 2009, 05:47) I ...   Jan 23 2009, 16:11
- - Axon   18/32 - there's a harshness in the left channe...   Jan 23 2009, 07:56
- - 2Bdecided   Found it... http://www.gearslutz.com/board/so-muc...   Jan 23 2009, 16:30
|- - Martin Kantola   QUOTE (2Bdecided @ Jan 23 2009, 10:30) My...   Jan 23 2009, 18:41
|- - krabapple   QUOTE (2Bdecided @ Jan 23 2009, 10:30) Fo...   Jan 24 2009, 01:01
|- - Martin Kantola   QUOTE (krabapple @ Jan 23 2009, 19:01) Bu...   Jan 24 2009, 03:11
|- - krabapple   QUOTE (Martin Kantola @ Jan 23 2009, 21:1...   Jan 25 2009, 00:08
||- - Martin Kantola   QUOTE (krabapple @ Jan 24 2009, 18:08) An...   Jan 25 2009, 00:28
|- - MLXXX   QUOTE (Martin Kantola @ Jan 24 2009, 12:1...   Jan 27 2009, 10:16
|- - krabapple   QUOTE (MLXXX @ Jan 27 2009, 04:16) The ef...   Jan 27 2009, 18:57
|- - MLXXX   QUOTE (krabapple @ Jan 28 2009, 03:57) Is...   Jan 28 2009, 14:14
- - 2Bdecided   Here you go... http://rapidshare.de/files/4332135...   Jan 23 2009, 17:25
|- - Martin Kantola   QUOTE (2Bdecided @ Jan 23 2009, 11:25) He...   Jan 24 2009, 07:13
- - 2Bdecided   Thank you Martin. Putting noise in the last 8 bit...   Jan 24 2009, 21:09
- - 2Bdecided   Remember those stats are only true for the situati...   Jan 25 2009, 17:38
|- - Martin Kantola   Thanks for the info David, I'm completely new ...   Jan 25 2009, 17:59
- - AndyH-ha   This was asked more than once but there was no res...   Jan 29 2009, 11:05
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