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-   -   Automatic dithering in PT 12.5? (http://duc.avid.com/showthread.php?t=396381)

jglunt2112 01-15-2018 10:42 PM

Automatic dithering in PT 12.5?
 
I normally record 88.2 and 24 bit in Pro Tools 12.5. I've been using Pro Tools for almost 6 years in a project studio, so while I'm far from an expert, I'm not a newbie either. A few weeks ago I was told by someone who is truly a Pro Tools expert that I don't need to dither when bouncing down from 88.2/24 to 44.1/16--that essentially Pro Tools does it automatically. Yet when I looked it up in the Pro Tools 12 reference manual, it said that I should dither (if I remember correctly; unfortunately, I'm not at a computer that has the manual). In fact, I believe it recommended dithering even if you weren't going to change sample rate and bit depth. Can anyone tell me exactly what's up with dithering? I understand there might be varying opinions out there, but does anyone actually know for sure? Thanks.

YYR123 01-15-2018 10:55 PM

Automatic dithering in PT 12.5?
 
Dither, when you change bit depth.

There is no other contrary opinion

Tell the guy who suggests you don’t need to do it, you won’t and do it anyway

Emi 01-15-2018 11:32 PM

Re: Automatic dithering in PT 12.5?
 
Dither is just added noise. IMO if you have a hardware inserted, like an analog compressor, on your main bus you can perfectly skip dithering. The inherent noise of an analog device can act like a dither. But I repeat, this is my opinion.

YYR123 01-15-2018 11:38 PM

Automatic dithering in PT 12.5?
 
It will take a smarter mind than mine to explain it but....

When you truncate the song the zeros in the silence add up to noise when the song is truncated (shrunk in bit depth), and not like a pleasing noise...like a hardware compressor

So dither moves that noise (idk how but it does) over to the inaudible zone for human hearing.


I read the Sonnox Limiter manual once or twice, about the matter.

But like I said I don’t really understand it, but that’s why is supposed to happen and the benefits of it

wwittman 01-15-2018 11:45 PM

Re: Automatic dithering in PT 12.5?
 
and while we are at it, 88.2's entire raison d'ętre (that it's "simple math to go to 44.1") is nonsense.

BScout 01-15-2018 11:45 PM

Re: Automatic dithering in PT 12.5?
 
Dither on bit depth changes downward (truncation.) Pro Tools auto-dithers in some instances (consolidating clips, for instance) but not bounce downs. Dither for the target bit rate by creating a master fader and throwing your dither plugin on that.

Don't need to dither if going up bit depth. Don't need to dither on sample rate changes (dithering before a SRC would just have the SRC applied to the dither which is a pointless exercise -- if the SRC is doing something special, it would have to have the dither built-in anyway because it'd need to be applied at a different stage in the processing and not the input file.)

Dithering going from 32 floating point to fixed point is pretty much pointless because of the audio level we're talking about and the fact it isn't pure truncation. But you can do it in that case if you wish. But pointless.

The one case it is obvious is going 24 fixed to 16 fixed. (your situation) so you should apply it if bouncing. If doing a clip consolidation or export clips as files, Pro Tools is already doing the dither (but not on a bounce down.) The matrix of applied dithers is in the user manual.

chrismeraz 01-16-2018 04:02 AM

Re: Automatic dithering in PT 12.5?
 
Pro Tools does apply dither automatically in some very specific situations that you don't need to worry about, such as after processing through upsampling plugins but before sending the audio to the Master Fader at the Session bit-depth. This is probably the source of your friend's confusion. You DO need to apply it (in some situations) when you bounce your files, because Pro Tools cannot guess what kind of dither you want or whether you want it at all, it depends on what you will do next with the file.

Fortunately, dither truly is one of the simplest decisions we have to make in our daily work. Unfortunately, there is still misinformation out there, much the same way some people believe the Earth might be flat...

Basic Principles:

1. Dither is 100% mandatory when converting audio to a lower bit-depth, if you wish to maintain the highest degree of quality technically possible from your source.

2. Dither is useless for any other situation.

3. No operation (other than bit-rate reduction) shall ever be done after applying dither. No level changes, no fades, no mastering, no converting to mp3 after dither has been applied.

If you have any doubts, please visit this link and see the video at the bottom of the page. The discussion on dither starts at 11:39, but honestly the whole video is incredibly important.

jglunt2112 01-16-2018 08:31 AM

Re: Automatic dithering in PT 12.5?
 
Thanks to each of you who responded. Special thanks to chrismeraz for the link to that video. My question was answered.
Jim

Rich Breen 01-16-2018 09:38 AM

Re: Automatic dithering in PT 12.5?
 
Quote:

Originally Posted by jglunt2112 (Post 2469244)
..Can anyone tell me exactly what's up with dithering? I understand there might be varying opinions out there...

Really no need for "opinions", it's well studied in plenty of areas other than audio. Dither must be applied on bit-reduction operations. The only room for opinion/preference is in whether you prefer unweighted dither or one of the dozens of weighting schemes out there.

There is often confusion between BTD and Export; Pro Tools *will* apply dither when *exporting* a file to a lower bit depth, Pro Tools *will not* apply dither on a BTD, so the user must handle any required dither for if targeting a bit depth lower than the session depth.

Quote:

Dither is just added noise. IMO if you have a hardware inserted, like an analog compressor, on your main bus you can perfectly skip dithering...
Hardware self-noise is not sufficiently randomized nor predictable enough to be relied upon for dithering. For a real understanding of dither, Vanderkooy and Lip****z's 1987 paper is definitive - still available at the AES: "Dither in digital audio. J. Audio Eng. Soc. 35, 966-975."

jglunt2112 01-16-2018 11:24 AM

Re: Automatic dithering in PT 12.5?
 
Thank you, Rich, especially for being specific about BTD & export as it relates to dithering.
Jim


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