Topic: 24bit to 16bit

[caymanreview]

if you need a wavelab 5.0 "demo" pm me

[BC]

just FYI:

NEITHER resampling or dithering should cause any changes in the levels or pops/clicks in the recording.
I think something is wrong with the software you are using.

Take care,
Ben

[creekfreak]

something is wrong.....never had this issue before, but then again, never did 24bit before either

[rustoleum]

It sounds like you are simply chopping off 8 bits to move the file from 24 bits to 16... the end result would be a rather harsh recording in some parts since the low-level detail is simply cut off... When dithering, those low-level sounds are preserved by essentially pushing pieces of them into the 16 bit world.  Dither your 24 bit recording (as oppossed to just saving it to a 16 bit file, which it sounds like is what you're doing) and I think all will be better.

[creekfreak]

It sounds like you are simply chopping off 8 bits to move the file from 24 bits to 16... the end result would be a rather harsh recording in some parts since the low-level detail is simply cut off... When dithering, those low-level sounds are preserved by essentially pushing pieces of them into the 16 bit world.  Dither your 24 bit recording (as oppossed to just saving it to a 16 bit file, which it sounds like is what you're doing) and I think all will be better.

I think you nailed the problem, that is exactly what happened.

[sygdwm]

fwiw. tim also told me to run pussy levels w/ 24 bit to leave headroom. crank the the shit out of your levels at 16 bit. i think.

[Tim]

where's that thread?

I think the confusion about where to set 24 bit levels was cleared up a bit.

16bit you need to run hot. 24bit I was always told to run a bit lower...

[Tim]

here's the thread...

http://www.taperssection.com/yabbse/index.php?topic=19485.90

start around page 7 and you'll see the relevant info on levels, posted by folks who are much smarter than I

[willfoy]

But maybe I'm getting the wrong message from the thread, but that is you can lower your levels for greater headroom, but not that you should lower your levels at 24 bit...

At any rate, after spending most of the last 18 months of my taping life in 24bit land, the pops and clicks are probably based on improper dithering. I use WaveLab to do mine, but Goldwave or SoundForge should do the job. CDWave's current incarnation does it as well, but I'm not pleased with the results in current production releases... Perhaps they'll improve over time.

[rustoleum]

Simply put, the digital world allows 6 db of dynamic information per bit.  So, a 16 bit recording allows 96 db of info, while a 24 bit recording allows 144 db.  Sooooo... when folks say you don't need to push the levels in 24 bit recording, this is simply because even if you're peaking out at -18 db you're still capturing 126 db of info which is still a higher resolution than a perfectly set 16 bit recording. 

You should still shoot to set levels perfectly as the more detail in the recording the better, but if it's a question of setting levels higher and potentially clipping the recording vs setting levels conservatively I'd go with a conservative set. 

[creekfreak]

But maybe I'm getting the wrong message from the thread, but that is you can lower your levels for greater headroom, but not that you should lower your levels at 24 bit...

At any rate, after spending most of the last 18 months of my taping life in 24bit land, the pops and clicks are probably based on improper dithering. I use WaveLab to do mine, but Goldwave or SoundForge should do the job. CDWave's current incarnation does it as well, but I'm not pleased with the results in current production releases... Perhaps they'll improve over time.

I think that was my problem, I was just saving the file back to 16bit, not applying any dither, will try that later tonight..

[BC]

Simply put, the digital world allows 6 db of dynamic information per bit.  So, a 16 bit recording allows 96 db of info, while a 24 bit recording allows 144 db.  Sooooo... when folks say you don't need to push the levels in 24 bit recording, this is simply because even if you're peaking out at -18 db you're still capturing 126 db of info which is still a higher resolution than a perfectly set 16 bit recording. 

Just FYI: no piece of recording gear comes even close to the theoretical 144 dB dynamic range of 24 bit PCM audio. For example I think the V3 is spec'd around 113 dB. But even with this, if your levels peak at -17dB (113-17=96) at 24 bit, you are  getting the same resolution as recording at 16 bit hitting 0. High resolution digital rocks!!!   

[dklein]

Vocab time:

Resampling = changing the sample rate (96 kHz to 44.1 kHz)
Dither = changing the bit depth (24-bit to 16-bit)

I'm having a hard time following what you're using to try to accomplish whatever it is you're doing.

Since we're trying to be precise, dither does not = changing the bit depth
Changing the bit depth is just that.  Others call it word length reduction or whatever.  It is simply throwing away the least significant bits, kind of like rounding off numbers.  You see 13.345679 on the calculator and you say 13.3 (except for that little rounding rule we use).  Same thing but in binary.

Dither is a mathematical technique used to capture detail that would not normally be captured at the reduced word length.  When you truncate from 24 to 16 bits, you're basically chopping off the last 8 bits.  On their own, these are only used to capture the very quietest sounds.  During a peak, they capture the finest info about the event, like the last decimal place in the number example above.  You can't chop the 8 bits on the other end of the 24 bit word because they cover all of the musical peaks so you chop the fine detail.

Dither involves adding some noise to raise those little bits up to the point where they will have an effect within the 16 most significant digits of the 24 bit recording.  Then you chop off the last 8 and you have some of that detail you wouldn't have had without the dither.  Noise shaping is about how you choose to apply the dither (out of scope!)

That's the theory on it.  With respect to levels, I try for peaks around -6 to leave room for the unexpected.  There's absolutely no point in going over.

Simply put, the digital world allows 6 db of dynamic information per bit.  So, a 16 bit recording allows 96 db of info, while a 24 bit recording allows 144 db.  Sooooo... when folks say you don't need to push the levels in 24 bit recording, this is simply because even if you're peaking out at -18 db you're still capturing 126 db of info which is still a higher resolution than a perfectly set 16 bit recording. 

True, but 24 bit recording benefits aren't limited to the additional dynamic range in the sense that you can record louder sounds or anything like that.  It's more like using a fine grain film or a higher image density in a digital photo.  You get a more detailed account of each sampling event.

That said, I have yet to prove its worth to myself.  I've been recording in 24 bit for over a year and just kind of do it on faith.  I can do 24 bit playback but I'm not sure that live shows are really the way to showcase the sonic capabilities of 24 bit.  Right now I can only playback 24 bit through an emagic A62 - I really don't know how good the d>a is.  Got something else coming soon but I guess I need to take a show and run A/B on the 16 and 24 bit through the same d>a.  hmmm...maybe I'll get on that.
<edited for spelling>

[Electric Cowgirl]

Creek-- Didn't see what software you are using, but here's some info just for the hell of it. 

If you are using Wavelabs open the masters window (view->specialized windows->masters section) apply the dither then click render in the mastering window.  This will give you a new file that is 16bit, and allow you to keep your 24bit master with one click.  Just in case you or anyone reading didn't know

[creekfreak]

thanks Becky, just got wave lab (thanks caymanreview!!!), will be trying it out soon