24 Bit more about resolution, not dynamics...

Posted: Mon Aug 28, 2006 4:19 pm

While technically it it true that 24bit gives you "more dynamic range", the real benefit is the increased resolution. You have to realize that an audio waveform is constantly passing from positive to negative, very quickly. in these microseconds you get down in the "crevices" near 0 physical amplitude, which is -inf in your DAW. This is where 24 bit helps; it allows you to capture more resolution of the zero-crossing points, and as a result you get more clarity. So the dynamics gained are downward; more resolution as you approach the computer's approximation of -infinity, or zero acoustic energy - which happens all the time, even when listening to a loud sustained sound. So its not just quiet passages that benefit - ALL the passages benefit!!!! They benefit a helluva lot Shocked

Forget about the dynamics gained as something that will allow to put more dynamics into your recordings. That is not the point and is the wrong way to look at it. More accuracy as the wave goes from positive to negative, more info, resolution, whatever you want to call it - that's the point. Hell, after compression (to reduce the dynamic range), 40 or so db is plenty of "dynamic range" in a rock composition, but is not good enough bit resolution. We have two notions going on here, and I hope this will help to start a discussion.

Peace,
Nate

Posted: Mon Aug 28, 2006 5:43 pm

It seems to me like you're saying that 24 bit recording allows you to capture more dynamic range than 16 bit recording.

I'd have to agree with that.

Posted: Mon Aug 28, 2006 6:28 pm

well, yes technically, but...
I am also saying that the benefit of this is the clarity at or around the zero-crossings, not having the ability of juxtaposing "quieter and louder sounds" which is how most people think of dynamic range.

For example take a 24 bit file, and the same file carefully converted to 16 bit. They will have the same "dynamic range", or RMS to Peak. They will sound the same loudness everywhere. They will generate roughly the same "statistics" so to speak. Two average listeners would probably not notice any difference...Where they would differ is that, in fact, the 16bit file is more "grainy" mathematically speaking. Less resolution. Whether it is 16 bit or 24 bit, it does not actually change the musical dynamics. It captures more detail in the voltage change through the time domain.

When you convert to 16 bit, you lose some of the detail, but you retain the dynamics of the composition perceptually. Its like the same picture, but with less pixels per inch. Red is still red, but that spot in the picture where the red shades into some other color...not as smooth if you were to zoom in.

So my point is, the extra dynamic range is a de facto benefit of 24 bit recordings, but is manifested at the micro level (zero-crossings) not the macro level (eg - having a trumpet at -120dB and a snare a 0dB). In this case, you would turn down to hear the snare at reasonable level, and the trumpet would disappear, completely inaudible. So the dynamic range is not really helpful or relevant in that sense. But, the snare hit, as it rips back and forth from positive to negative, will have more detail encoded about those crossing points in 24 bit than it would in 16 bit. THIS increase in resolution to the original sound is why higher bit depths are good. This is the advantage a higher bit depth gives you.

Peace,
Nate

Posted: Mon Aug 28, 2006 6:35 pm

CrackBuddha wrote:

well, yes technically, but...
I am also saying that the benefit of this is the clarity at or around the zero-crossings ...

which is what dynamic range is all about.

Posted: Mon Aug 28, 2006 8:36 pm

well well... seems i've stumbled into something here... personally i've always found the resolution arguement interesting.... and i tend to agree with it... perhaps with a little different view.... electronically we start at an analogue level .. and not withstanding increases in rail voltages over the years we can assume that the max/min that we display haven't changed... the noisefloor of the thing is still at ?? the max swing is still +/- 18V... so in that sense we dont have anymore dynamic range... at the point of conversion we stop time for in all intents and spit out a #which represents the nearist we can come to incrementally... so the resolution arguement then boils down to how many slices do we want to deal with in the verticle plane (amplitude)... the same arguement holds true for sample rate...on the horizontal if you will...

Posted: Mon Aug 28, 2006 9:53 pm

Excellent topic Nate!!

I couldn't agree with you more.

True, the signal to noise ratio is increased significantly, and this is a HUGE benefit during mixing and while applying effects. The true benefit comes from the nature of 24 bit being able to represent a higher quantity of voltage levels resulting in lower quantization errors. It's kind of like Mozart dynamics versus Mahler dynamics - both have PPs and FFs, but for Mozart to have gotten from a P to an F, he would have scored for more instruments whereas Mahler was able to (thanks mostly to musical instrument advances over the course of the 135 years) create P with a full orchestra as well as every dynamic in between it and FFFFFF...

Mozart was stuck with something resembling terraced dynamics and Mahler was free to write for an infinite level of dynamics.

Of course, that doesn't invalidate the beauty that is Mozart (and by analogous extension - CD), it simply shows the more simplistic nature.

In general, it isn't the lower noise floor and greater dynamic range of 24 bit that people hear as more pleasing, it is the greater clarity of dynamics represented within the scope of that range. So, not *DYNAMIC RANGE* per se, but dynamic accuracy.

J.

Posted: Wed Aug 30, 2006 9:45 pm

dementedchord wrote:

the max swing is still +/- 18V...

now that's something I'd like to see - a delta-sigma A/D converter with a 36 v reference. That would add another 3 bits or so of resolution to the current 24 bits. ('course, voltages like that would probably punch right through the silicon)

One of the problems designers face is the ever-lowering maximum voltage levels on silicon. Years ago we'd have 15 v references on A/Ds, then 10, now 5, some probably down to 3.3. The problem is that the system noise floors aren't really changing.

24 bit is way beyond what we need from a dynamic range perspective but the resolution brings its benefits.

Posted: Wed Aug 30, 2006 10:48 pm

understood but that's out of context in no way did i talk about +/- 18 v as the reference voltage for theconvertor... what i was observing was more along the lines of general levels that we come from and eventially must return to ... incedently the general discussion was not specific to sig-delta type 1 bit convertors but pcm...

Posted: Thu Aug 31, 2006 12:10 am

The digital geeks like Nika and Bob.K and others ... including the Digi boys themselves ( Dave LB )
have often said that resolution in the way you have used it to describe PCM encoding is incorrect.

they say that 24 bit is not more resolute than 16 bit
it does provide for more dynamic range if required
if the signal is of low dynamic range then the detail of the sound at the given sample rate will remain the same.

I don't want to get into another deep discussion as we have done this so many times in the past.
Try some searches here and look for some of the very, very, old threads from the im and distant past with some og the guys from PSW and Gearslutz when they were mods he at RO.
... and some of the old stuff at Sweetwater Forum

Read some of the Bob K and Lavry notes and white papers and some of the Chip manufacturer white papers etc

Ultimately we will all use a new sytem and DSD could be it ... not yet though.

Posted: Thu Aug 31, 2006 1:18 am

yeah i'm aware of katz and lavery and aldridge to alesser degree ... just not sure why rexamining it from a slightly different perspective is such a bad thing... i always have thought anything worth defending should be worth rexamining...

if the signal is of low dynamic range then the detail of the sound at the given sample rate will remain the same.

am i to understand you to say that as an example a micro volt change at two different levels are not represented in the same way??? seems counterintuitive...

Posted: Thu Aug 31, 2006 7:42 am

Yep, and I've gone on record several times disagreeing with these folks. My feeling is, the burden of proof is on them. They are trying to suggest that something is not how science and basic math (and some not so basic quantum physics) state that it is. Therefore, if they state otherwise, it is on them to back up their statements. This is something they have NOT done. They (both Dan and Nika) never get around to explaining WHY they suggest that higher resolution doesn't mean less errors (rounding/quantization) rather they go and explain why it means better noise floor/SNR.

Sorry, but just because Dan and Nika say it's so doesn't make it so. There's a lot of really simple math involved here. It's not as complicated as either of these gentlemen would have you believe.

In 24 bit or 16 bit 0=0 and granted there are 8 more bits on the "high" end of the binary spectrum of 24 bit, but that certainly does not mean that all of these 1s and 0s only affect the maximum or minimum amplitude of any given signal.

One good analogy is the bit range on digital photography. In 8 bits per color channel (24 bit), there are a certain amount of colors available. In 12 bits per channel (36 bit), there are significantly more colors available. This doesn't make blue any less blue, but if you take a picture in 24 bit of an image which is darn-near blue, you'll probably just get blue. However, in 32 bit, you will get "darn-near blue."

The fact is, with digital ANYTHING, audio, imaging, etc., the more values (in digits) you have, the more resolution between primary values you have.

What they're suggesting is that the ONLY difference between 4 bit audio (think Atari) and 16 bit audio is the SNR. Is this not absurd?

Are they suggesting that you reach a critical mass at some point and that point is clearly 16 bits? So, with 1 bit, 2 bit, 4 bit, and 8 bit audio, each incremental increase gains resolution, but once you hit that magical 16 bit threshold, you no longer gain resolution but only SNR?

No offense to either Dan or Nika, as I respect them greatly, but their arguments border on the insane. To me, it's apparent that they are attempting to put science before logic. Neither can exist without the other.

Sorry...Rant over.

Posted: Thu Aug 31, 2006 8:00 am

Yea? Well... my DAW goes to 25 bit. That's more resolution than 24.

Posted: Thu Aug 31, 2006 8:13 am

corrupted wrote:

Yea? Well... my DAW goes to 25 bit. That's more resolution than 24.

Oh yeah?!?! Well I record everything at 2 bit. It saves hard drive space!

Posted: Thu Aug 31, 2006 8:16 am

Cucco wrote:

corrupted wrote:

Yea? Well... my DAW goes to 25 bit. That's more resolution than 24.

Oh yeah?!?! Well I record everything at 2 bit. It saves hard drive space!

DIZZZAMN! Foo, you workin' fo ATARI up in this piece?

(Sorry to crap up your thread, I had a Spinal Tap moment and I apologize...)

Posted: Thu Aug 31, 2006 8:24 am

corrupted wrote:

Cucco wrote:

corrupted wrote:

Yea? Well... my DAW goes to 25 bit. That's more resolution than 24.

Oh yeah?!?! Well I record everything at 2 bit. It saves hard drive space!

DIZZZAMN! Foo, you workin' fo ATARI up in this piece?

(Sorry to crap up your thread, I had a Spinal Tap moment and I apologize...)

Fo Shizzle DAWG!

Besides, it ain't my thread you're "crapping up" (?) - I'm just here to bitch-slap conventional wisdom.

Cool

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