Dither confusion

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Re: Dither confusion

Post by RichardT »

MOF wrote:Hugh and CS70, is the 64bit value something that has to be set in Cubase?
I thought floating and fixed point values were something set by the program coders.
I have Logic X , I know of no setting other than ticking 24bit to replace the standard 16bit rate.

Yes in Cubase, it’s possible to choose whether the audio engine works at 32 or 64 bit float.
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Re: Dither confusion

Post by CS70 »

I stand corrected. Fun. Guess it may help a little with performance and RAM usage.
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Re: Dither confusion

Post by MOF »

Yes in Cubase, it’s possible to choose whether the audio engine works at 32 or 64 bit float.

I presume that’s on the PC to match the plugins, all modern Macs run at 64bit and support for 32bit was dropped a while ago.
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Re: Dither confusion

Post by RichardT »

MOF wrote:
Yes in Cubase, it’s possible to choose whether the audio engine works at 32 or 64 bit float.

I presume that’s on the PC to match the plugins, all modern Macs run at 64bit and support for 32bit was dropped a while ago.

No, that’s something different - 32 bit addressing. Cubase is a 64 bit app on all platforms in that sense and only supports plugins with 64 bit addressing. The 32 / 64 bit choice in Cubase is about the word length of the data.
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Re: Dither confusion

Post by merlyn »

These are a couple of points I have found make dither more understandable :

- Hardware is 24 bit

When you hear playback from your speakers the digital audio has been truncated.

- Dither is part of PCM audio

Dither turns a non-linear system into a linear system with a small amount of noise. Quantisation error is correlated with the signal -- that means it is distortion which means in its raw state PCM is non-linear. Adding dither gets rid of quantisation distortion making the system linear at the price of a small amount of noise.

With 16 bit recording dither was added before the A/D process. With 24 bit that is unnecessary because the noise from analogue electronics serves as dither.

A question I've seen more than once is from people who want to use hardware effects as inserts in their DAW. A track goes out through the D/A, through the hardware, and back in through the A/D. Should that be dithered on the way out? Yes.

For an application like this, where dither might be used more than once on the same audio, it's recommended to use triangular dither.

For the final dither it's recommended to use noise shaped dither.

The question is then -- what do you want a 24 bit file for? If this is to be given to e.g. a mastering engineer then you could export at 64 bit float and you wouldn't need dither.
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Re: Dither confusion

Post by worshiptuned »

RichardT wrote:That’s the recording bit depth? As soon as you apply gain changes or any processing to that channel, though, the signal is going to be at 32 or 64 bit float, irrespective of the recording bit depth.

yes but then, after this real time processing at 32bit float or 64bit float the file is recorded at the set recording bit depth. Then for the dithering you have to consider the recording bit depth
from Cubase manual
see the paragraph Bit Depth

source:
https://steinberg.help/cubase_pro/v10/e ... log_r.html
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Re: Dither confusion

Post by worshiptuned »

CS70 wrote:Guess it may help a little with performance and RAM usage.

Greg Ondo of Steinberg explains at 48:55 that the 64 bit float processing precision is intended for recording at 32bit integer, some Steinberg soundcards have this option, I think also others as Merging Anubis. He says he made a blind test and there is a better audio quality (subjective)

https://www.youtube.com/watch?v=RFXBscdP5nQ
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Re: Dither confusion

Post by RichardT »

worshiptuned wrote:
RichardT wrote:That’s the recording bit depth? As soon as you apply gain changes or any processing to that channel, though, the signal is going to be at 32 or 64 bit float, irrespective of the recording bit depth.

yes but then, after this real time processing at 32bit float or 64bit float the file is recorded at the set recording bit depth. Then for the dithering you have to consider the recording bit depth
from Cubase manual
see the paragraph Bit Depth

source:
https://steinberg.help/cubase_pro/v10/e ... log_r.html

Yes, and if you add processing to the recorded track after you’ve recorded it, it will be back at 32 bit or 64 bit float!
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Re: Dither confusion

Post by worshiptuned »

RichardT wrote:
worshiptuned wrote:
RichardT wrote:That’s the recording bit depth? As soon as you apply gain changes or any processing to that channel, though, the signal is going to be at 32 or 64 bit float, irrespective of the recording bit depth.

yes but then, after this real time processing at 32bit float or 64bit float the file is recorded at the set recording bit depth. Then for the dithering you have to consider the recording bit depth
from Cubase manual
see the paragraph Bit Depth

source:
https://steinberg.help/cubase_pro/v10/e ... log_r.html

Yes, and if you add processing to the recorded track after you’ve recorded it, it will be back at 32 bit or 64 bit float!

Yes thanks, you are right, it's confusing.
This is why they suggest in order to keep the best audio quality and avoid clipping, to set the recording bit depth also to 32 bit float, when recording with effects.
Then in Cubase is the bit depth to consider when dithering, whenever some processing is applied, 32 bit float or 64 bit float, even if there is a different recording bit depth? :think:
The Elf said differently :!::?:
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Re: Dither confusion

Post by Hugh Robjohns »

All DAWs process internally at either 32-bit floating point or (more recently) 64-bit floating point.

Any sources that you process internally (even if that's just a volume change) will grow in wordlength to one of those formats, and any tracks that you bounce or re-record internally will normally (and sensibly) be stored at one of those formats too.

However, the physical outputs (and inputs) are normally in a 24 bit fixed point format (or 16 bit for some legacy applications).

And any word-length reduction always requires dithering to prevent quantisation distortion.

The mantissa in a 32-bit float format is 24 bits so, in theory, any internal processing should already involve dithering to maintain the 24 bit mantissa accurately. That being the case, if you get your gain structure right that mantissa can be passed directly to a 24-bit fixed point output without further redithering.

The same is not the case with 64-bit floating point which has a larger mantissa.

If in doubt, redither at 24 bit anyway... at worst you'll raise the digital noise floor by a few dB (but it will still be below the actual noise floor of your D-A converter), and it will guarantee nothing nasty happens during fades.
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Re: Dither confusion

Post by worshiptuned »

Hugh Robjohns wrote: The mantissa in a 32-bit float format is 24 bits so, in theory, any internal processing should already involve dithering to maintain the 24 bit mantissa accurately. That being the case, if you get your gain structure right that mantissa can be passed directly to a 24-bit fixed point output without further redithering.

The same is not the case with 64-bit floating point which has a larger mantissa.

If in doubt, redither at 24 bit anyway... at worst you'll raise the digital noise floor by a few dB (but it will still be below the actual noise floor of your D-A converter), and it will guarantee nothing nasty happens during fades.

I appreciate! Now is much clearer!!! :thumbup:
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Re: Dither confusion

Post by CS70 »

worshiptuned wrote:He says he made a blind test and there is a better audio quality (subjective)

I guess... :)

Using double vs float simply changes the size of the unavoidable approximation errors present in every real-numbers numerical calculation made with a digital computer. Assuming that the mixing engine (as it must) uses numerically stable and good algorithms, even with single precision these errors will be very small. With double precision they will be even smaller... which in turn may make an occasional difference to what gets rounded to integers for D/A conversion, ultimately leading to a difference in sound, especially for minute details. So it may be that someone can perceive a difference. I am pretty sure I wouldn't perceive any. :D
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