The 24-bit challenge

Ill do it. Will email.. though I really dont think a simple volume up/volume down is enough error accumlation to really take advantage of the superiority of 24-bit.

xoxo
 
Hold up.

Do you really understand bit depth? I ask merely for information, you understand. I dont claim to know much about it, really.. but I can do math, and I have a working knowledge......

so let me get this str8:

You recorded a sound... as close to unity as you could get. 24/441.

Then you copied it.

Then you dithered this UNPROCESSED sound....(copy A)

Then on a copy.. you TRUNCATED this UNPROCESSESSED sound.(copy B)

then you did a couple volume processes on a 16-bit sound??(c, D, and E)??

I must say, this is a completely non-scientific and useless test, and Ill tell you why.

A and B will be virtually identical. you arent processing the sound.. thus there are NO rounding errors... you basically are testing the difference in sound between truncating and dithering here.... which will be minimal . . . and subjective.

Now, for c, d, and e...
Where do you get the idea that 6db = 1 bit?? If I drop volume be 18db.. Im NOT chopping 3 bits off... Im NOT dithering.. Im NOT truncating... basically Im filling those last 3 bits with ZEROs. Which is MUCH different then chopping the bits.. because when I bring the volume back up... the sample can use those bits again!! they are STILL THERE!!! so your volume changes seem extremely minimal to me... maybe you introduce a little rounding error.. but its only two moves, dude.

maybe Ill do my own test, now that Im so annoyed at people's even-more-shallow-than-my-own understanding of this matter. But not anytime before April ;)

xoox
 
camn,

> I must say, this is a completely non-scientific and useless test ... A and B will be virtually identical. ... you basically are testing the difference in sound between truncating and dithering here. ... which will be minimal . . . and subjective. <

Actually, this is quite scientific. According to a lot of people, the whole point of 24-bit recording in a 16-bit CD world is that after dithering, the result is better than just using 16 bits in the first place.

> Where do you get the idea that 6db = 1 bit?? <

And where did you get the idea that 6 dB. is NOT one bit? :)

> If I drop volume be 18db ... Im filling those last 3 bits with ZEROs. Which is MUCH different then chopping the bits. <

No, it's exactly the same. Since audio programs won't play a 13-bit file, the only recourse is to leave the file at 16 bits but zero out the lower bits. Which is just what I did.

> because when I bring the volume back up... the sample can use those bits again!! they are STILL THERE!!! <

Yes, they are still there, but they're all zeros! To take this to the extreme: Suppose I drop the volume by whatever it takes so only one bit is active, and then raise it back up. What do you think it will sound like? Do you see the point now?

--Ethan
 
I believe that the methodology used to produce the .wav files may be flawed. I do understand the db level = resolution thing, and theoretically this should work, but you really don't know what's going on in the software.

When you lower the volume, SoundForge may be saving those extra bits almost like a "level of undo" and simply replacing them when you then raise the volume. What assurances do you have that you're actually losing resolution? What was the procedure in between the lowering/boosting db level?

Also, I find that a highly dynamic voice, and in some cases, live drums are the most revealing sources for such a test. Acoustic guitar passages without much dynamics don't do much for me.
 
Please let me participate

camn,

> I must say, this is a completely non-scientific and useless test ... A and B will be virtually identical. ... you basically are testing the difference in sound between truncating and dithering here. ... which will be minimal . . . and subjective. <

>Actually, this is quite scientific. According to a lot of people, the whole point of 24-bit recording in a 16-bit CD world is that after dithering, the result is better than just using 16 bits in the first place.

NO, the processing is done at 24 bit -> the processing uses the extra bits... hence the quality difference... and then you go to 16 bit.

> Where do you get the idea that 6db = 1 bit?? <

>And where did you get the idea that 6 dB. is NOT one bit?

You CANNOT say that it's "quite scientific" when you try to dismiss a serious question by a lame joke.


> If I drop volume be 18db ... Im filling those last 3 bits with ZEROs. Which is MUCH different then chopping the bits. <

>No, it's exactly the same. Since audio programs won't play a 13-bit file, the only recourse is to leave the file at 16 bits but zero out the lower bits. Which is just what I did.

> because when I bring the volume back up... the sample can use those bits again!! they are STILL THERE!!! <

>Yes, they are still there, but they're all zeros! To take this to the extreme: Suppose I drop the volume by whatever it takes so only one bit is active, and then raise it back up. What do you think it will sound like? Do you see the point now?


--Ethan

guhlenn
 
Let me comment on this. I don't know the scientific jargon as well as some of you. But I am sort of an audiophile and I can tell you flat out that I can tell the difference between 16 bit A/D's and 24 bit A/D's Is this the same thing? I have several audio burners; some of which have 16 bit A/D's and some have 24 bit A/D's and there is definately a difference and in fact I hear differences between A/D's of different manufacturers even when the bits are the same. I guess I'm gonna find out that this is totally different that recording resolution; :( but I wanted to make the observation and if it is different; will someone please explain to me about A/D and D/A bit rates as opposed to recording word length bit rates. :confused:
 
Dolemite,

> When you lower the volume, SoundForge may be saving those extra bits almost like a "level of undo" and simply replacing them when you then raise the volume. <

Excellent point. But in this case, SoundForge is not doing that. I specifically faded out the very end of each Wave file to hide the noise that became more and more obvious as the bit depth was reduced. So you can't hear the change in that part of the Wave files, but I sure could. Which convinced me that SoundForge was in fact doing what I expected it to.

> Also, I find that a highly dynamic voice, and in some cases, live drums are the most revealing sources for such a test. Acoustic guitar passages without much dynamics don't do much for me. <

Okay, I'll use those for the next test. :)

--Ethan
 
guhlenn,

> NO, the processing is done at 24 bit -> the processing uses the extra bits... hence the quality difference... and then you go to 16 bit. <

I'm not sure what you are saying here. All I did was reduce the bit depth of the files. There was no other processing.

> You CANNOT say that it's "quite scientific" when you try to dismiss a serious question by a lame joke. <

Not a lame joke at all. It is a fact that each bit represents 6 dB. of dynamic range. How is the test unscientific? The point is to see how many people can hear the difference between various bit depths in a totally blind test. Does this test not do that? Please listen to the files yourself and send me an email with your answers.

--Ethan
 
Bob,

> I can tell the difference between 16 bit A/D's and 24 bit A/D's Is this the same thing? <

Can you tell the difference using only the 24-bit A/D when one file is recorded at 24 bits and another is at 16 bits? If not, then the real issue is the quality of the two different A/D convertors, not the bit depth itself.

--Ethan
 
Ethan,

I've found that in wavelab when I process dynamic changes, it maintains the lost resolution while you're working, such that if you crank the level back up, it sounds identical to the source. I verified this by cutting a 16bit file by 90db, "applying" the processing (e.g. creating a new temp wave file), and then increasing the gain by 90db and applying the processing (creating another new temp file). It should have sounded like "ckejrkadslfkjadsflkajfdfasdrer" but it sounded like the original. The key was to actually *save* the file after each application. I'm not sure how soundforge works, but I figured I'd bring this to your attention just in case. Sorry to interrupt!

Slackmaster 2000
 
...

I think what Camn was pointing at is that you have to do the recording (i.e. the AD conversion) using 16bit and 24bit. Whatever sound file you get after dithering or truncating the 24bit file has to be compared to the file recorded at 16bit ...

I don't know poo about this topic but it's quite interesting to get into. If my above paragraph is nonsense, feel free to call me an idiot.
 
Another point I'd like to make. The actual usable range of a 16bit system will not be a perfect 96db. However, you can (or you better be able to) get a perfect 96db when recording at 16bit using 24bit converters, because the converters are still working at 24bit. So comparing this test to testing seperate 16 and 24bit converters isn't exactly correct.......HOWEVER, I agree with Ethan that you can't compare two different sets of converters, because you suddenly introduce too many uncontrollable variables.

Slackmaster 2000
 
This is a very interesting thread and for the most part I have enjoyed reading it.... BUT...

Can you all quote each other with the proper method..

All im seeing is sentences starting with this ">"...

Fucking Annoying...

I don't know who is saying what..... OK well I do, but It's given me a headache trying to seperate each person..
 
I have a side question here, it just popped into my head.

What does a 24 bit soundcard do when it plays a 16 bit CD or a .wav file? Do the cards have dual converters and automatically sort the incoming digital infomation to the proper converter? Or does the 24 bit card resample the 16 bit data into the 24 bit format? When your monitoring your PC during mixdown are you listening to a 24 bit mix or a 16 bit mix? Or does the cards allow you to hear a 16 bit dithered signal whatyouhearwhatyouget mix so that the CD will playback exactly what you mixed?


Peace,
Dennis
 
Why is this even an issue? The advantages to 24bit and the increase in SNR is pretty obvious to anyone who uses 24bit. This isnt an esoteric theoretical issue. Just use your ears.

Why wouldnt you use 24bit? Harddrives are dirt cheap now so storage isnt that big of an issue. Why even worry about it?

If you want a real test listen to reverb created in 16 vs 24bit. THEN you will really hear the difference.
 
Slack,

> I've found that in wavelab when I process dynamic changes, it maintains the lost resolution while you're working <

SoundForge doesn't seem to do that, because the lower resolution was very audible as the last chord faded out. Of course, I faded the files on my web site before that point!

> The actual usable range of a 16bit system will not be a perfect 96db. <

Agreed, but how many studios have an ambient noise floor even close to that?

--Ethan
 
VOX,

> Can you all quote each other with the proper method.. <

I agree. I go out of my way to address each person by name. In newsgroups this is less of a problem because you can see the thread order. But here, all the replies are stacked one after the other in the order they were posted, not the order of conversation.

--Ethan
 
Tex,

> This isnt an esoteric theoretical issue. Just use your ears. <

Okay, so please do that and let me know which file is which!

> Why wouldnt you use 24bit? Harddrives are dirt cheap now so storage isnt that big of an issue. Why even worry about it? <

Hard drives are indeed cheap, but throughput is still not unlimited. If someone can get only 12 tracks at 24 bits they could probably get 18 tracks at 16 bits.

> If you want a real test listen to reverb created in 16 vs 24bit. THEN you will really hear the difference. <

Yes, others have suggested this too. That test will be next.

--Ethan
 
Ethan Winer said:
I specifically faded out the very end of each Wave file to hide the noise that became more and more obvious as the bit depth was reduced. So you can't hear the change in that part of the Wave files, but I sure could. Which convinced me that SoundForge was in fact doing what I expected it to.
Click to expand...

SoundForge doesn't seem to do that, because the lower resolution was very audible as the last chord faded out. Of course, I faded the files on my web site before that point!
Click to expand...

Well, then you're already masking the difference! What good is resolution without dynamics?

> Also, I find that a highly dynamic voice, and in some cases, live drums are the most revealing sources for such a test. Acoustic guitar passages without much dynamics don't do much for me. <

Okay, I'll use those for the next test. ;)
Click to expand...

I look forward to hearing it! I think the differences would become more apparent.


I found this test, done be Keyboard Magazine, to be interesting at least:

http://archive.keyboardonline.com/features/bitwars/bitwars.shtml

I surprised myself and identified the original bitrate of 4/5 of the clips.
 
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