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Mason wrote: Wed Jan 10, 2024 2:28 pm We probably can't hear the dither noise at all, but we all hear differences between the 24-bit varieties in Ditherbox. Or having it on in a 24-bit mode vs having it bypassed.

Then there's some major truncation distortion happening for some reason, or it's doing something else to the bits greater than the LSB.

I'd be curious what sort of audio it would produce if you ran one bounce with dither, one bounce without dither, and then did a polarity inversion and summed them to get the difference signal.

Mason wrote: Wed Jan 10, 2024 2:28 pm

Nate Dort wrote: Wed Jan 10, 2024 1:50 pm For a 24 bit word, that's -144 dB. I call BS on people who claim they can actually hear that.

We probably can't hear the dither noise at all, but we all hear differences between the 24-bit varieties in Ditherbox. Or having it on in a 24-bit mode vs having it bypassed.

This is subtle stuff for sure—I hope I didn't come off all YouTube-style like "This One MISTAKE is RUINING your MIXES," I just thought it was good info—but it's no more made-up than hearing differences between Big Muff/Rat variants or something.

I've never understood how the inherent noise floor in the recording, which is almost definitely higher than -96dB in 16bit and absolutely higher than the -144dB in 24, isn't enough noise to provide for that last single bit of dithering. I guess if you were fading it out to a true digital silence you might get a few samples at the end that were truncated to a incomplete bit value or however the scientists that lie about vaccines explain Steely Dan. I almost definitely misunderstand the entire problem and hate Steely Dan. I've never noticed a difference from the days when placing dither as the last thing on your master bus was a thing and now where I never ever think about it. Also, if it is a thing that is so important, why wouldn't a DAW just do it for you at render? NASA is a lie Mr. ProTools!

Dither nerd here (I have a thesis student writing her own dither in C++ as I write this - she is in conversation with Chris from Airwindows and he has been super duper generous with his time).

A couple of raw statements, then an attempt at a non-technical explanation.

When downsampling, you absolutely need to dither. Not doing so will result in truncation distortion and quantising errors.

Your DAW _does_ dither for you automatically. When you export (and downsampling involves exporting), you will always - well nearly always - be dithering. Unless you turn dithering off that is.

Dither will be set to ON, most likely triangular probability density function (tpdf) dither, by default in your DAW. In most DAWs, the dither settings are available under the export settings. If you are not tragically obsessed with this sort of stuff, your eyes have probably just glazed over these settings as you exported. This is an appropriate response.

This is why no one talks about dither much any more, because it is baked in and you can ignore it.

Or you could not.

Here is an experiment that everyone can try. Get a high-res file of a track with some good dynamic range. I like to use a 96/24 render of Dire Straits' "Ride Across the River", but most things will do. Do it to Shellac. Import the track into your DAW. Then export it at 44.1/16, and with _no_ dither. (You might need to do a quick google search to find out how to turn off your DAW's built in dithering function if it is not somewhere obvious at export).

Now give it a listen at a nice loud volume. Sounds like crap right?

There are two things at work making it sound like crap:

1) Truncation distortion at the loud parts.

2) Quantising errors at the quiet parts and transient tails (which are really just other quiet parts).

(1) is happening because the loss of dynamic range resulting from the move from 24 to 16 is cutting off the peaks. There is no dither to smooth things out, so you can hear the clipping.

(2) is happening because the rounding errors are far enough above the noise floor that we can hear them.

By way of an analogy to help explain (2) a little more, think of digital images or a digital display or a digital movie file. It is when the image is at its most simple - the sky, someone's skin, water on a lake, and so on, that we start to notice the limitations of the digital render. You can see the wobbly parts. As it is with digital images, so it is with digital sound.

A full explanation of how dithering fixes (1) and (2) involves a bit of a deep-dive into Word Length, and Least Significant Bits. I'll spare everyone unless you want the gory details. Think of it as adding stuff so that the weird digital things happen beyond the range of human hearing.

Here is a second experiment that everyone can try. Do again as above - but this time add a dither plugin as the very last plugin on your master buss. It is important that you have done both of the following - (a) downsampled from high-res to 44.1/16, and (b) turned your DAW's in-built dither OFF. You need to turn off your DAW's in-built dither so that you can hear the result of the plugin dither that you have added at the end of your master buss. Otherwise you would be adding one dither on top of another dither, which is just perverse.

Once you have done this, you can start exporting the downsampled file repeatedly, each time with a different dither (Chris from Airwindows makes many), and compare the results with each other, as well as with exports dithered by your DAW's built-in dither. If you use Ableton, you will have the option (under "Dither options" in the export pop-up window) between rectangular and triangular dither (as well as some others).

Then report back here! You might be surprised just how different some of the exports sound from each other.

If you really are surprised and can hear the difference, then you are pretty much fucked because now you will start worrying about dithering.

: )

Kniferide wrote: Wed Jan 10, 2024 4:15 pm Also, if [dither] is a thing that is so important, why wouldn't a DAW just do it for you at render?

Reaper doesn't default to dither On with rendering, but rendering doesn't necessarily mean changing bit rate/resolution (as I already noted I try to keep a project consistent from start to finish) and why add noise (albeit probably harmless noise) if you don't need to.

At this point I only bounce down to 16/44.1 if I'm doing throwaway shit like practice recordings to keep the files as small as possible for email/dropbox. I check the dither box On just because it's there but for those recordings I wouldn't care much either way. If there were to be a run of pressed CDs I'd let a real mastering engineer do that conversion, as there are additional QA steps in the process as well.

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That was helpful. I ma try some stuff this weekend.

penningtron wrote: Thu Jan 11, 2024 8:08 am

Kniferide wrote: Wed Jan 10, 2024 4:15 pm Also, if [dither] is a thing that is so important, why wouldn't a DAW just do it for you at render?

Reaper doesn't default to dither On with rendering, but rendering doesn't necessarily mean changing bit rate/resolution (as I already noted I try to keep a project consistent from start to finish) and why add noise (albeit probably harmless noise) if you don't need to.

At this point I only bounce down to 16/44.1 if I'm doing throwaway shit like practice recordings to keep the files as small as possible for email/dropbox. I check the dither box On just because it's there but for those recordings I wouldn't care much either way. If there were to be a run of pressed CDs I'd let a real mastering engineer do that conversion, as there are additional QA steps in the process as well.

Reaper is not default on?? I write this scandalised….

Reaper has a box in addition to dither called Noise Shape, which I don't think I've ever used..

penningtron wrote: Thu Jan 11, 2024 4:46 pm Reaper has a box in addition to dither called Noise Shape, which I don't think I've ever used..

Noise-shaping transforms the dither from random to non-random. As to which is best/preferable, this depends on the program material. A contemporary Ministry track will have different needs than will a string quartet for example. With the former it is very unlikely that anyone would be be able to tell the difference between different noise shaping algorithms, whereas the with the latter one would most likely if listening carefully. Give them a go!

Signed up for a ‘one plugin a year’ Airwindows script to give tapedither a try for outboard stuff.

The only plugin I’ve used was Reainsert so excited to see how this works, except I will be working an insane schedule at work for a couple months, so I won’t make much progress for a while.

Solid! I've not used Tapedither so am super curious : )