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#11
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Re: Stereo Dithered Mixer
Isn't PT9 (non-TDM) using the 32-bit floating-point DAE engine from LE/MP?
Doesn't that render discussions of mixer internal dithering moot? I don't mean dithering for output bit rate reduction, just internal workings of the mixer. ...or am I full of it? Larry |
#12
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Re: Stereo Dithered Mixer
Larry, you're correct. "Regular" PT9 (and isn't there a PT9 MP now? ) uses a 32-bit floating-point engine, HD Native uses a 64-bit float engine, and TDM-enabled HD uses a 48-bit fixed-point engine. Since floating-point data can't be dithered by definition, this thread only applies to non-Native HD, which is what the OP appears to be using.
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David J. Finnamore PT 2023.12 Ultimate | Clarett+ 8Pre | macOS 13.6.3 on a MacBook Pro M1 Max PT 2023.12 | Saffire Pro 40 | Win10 latest, HP Z440 64GB |
#13
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Re: Stereo Dithered Mixer
Quote:
You are taking Nika's statement a little out of context in this particular instance. The potential problem that the dithered mixer was created to fix was due to repeated truncations. For example going from a series of 48bit plugs and truncating each time the signal was returned to the 24bit data path and also when the sizes of mixes exceeded a single dsp chip. In fact Nika did some tests himself and said the effect was noticeable (albeit under extreme conditions). Dither gets pretty complicated the more you look into it as in reality it's not really noise but a mathematical statistical construct (a Triangular Probability Density Function). So when you start doing a whole series of truncations it's possible that the statistical probability could be affected. It's also possible some correlations might occur but alternatively constantly summing multiple dither operations could have some audible effect on the level of the noise floor. Anyway, that was a discussion for a decade ago, I'm not sure if anybody is particularly bothered today but in case they are, they can try out the dithered mixer for themselves! G |
#14
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Re: Stereo Dithered Mixer
Thanks! I love learning more about this stuff. I'll have to re-read that chapter and see if I can figure out where I went awry in my understanding.
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David J. Finnamore PT 2023.12 Ultimate | Clarett+ 8Pre | macOS 13.6.3 on a MacBook Pro M1 Max PT 2023.12 | Saffire Pro 40 | Win10 latest, HP Z440 64GB |
#15
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Your understanding isn't wrong under normal conditions but this wasn't a normal condition. The manual application of dither is a one shot use during mastering or, the dither applied during ADC or DAC reconstruction. But in this instance we are talking multiple successive truncation operations and summing the results!
The only part of what you said which was definitely wrong was that dither is noise that has been shaped. TDPF dither is not noise shaped and you would only use noise shaped dither in a final re-quantisation process (usually the final stage of mastering). G |
#16
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Re: Stereo Dithered Mixer
Quote:
BTW, that thread you linked to wasn't about dither but it was fascinating. I wish Lynn Fuston were still active here. I've sat in on his sessions. He really knows his stuff.
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David J. Finnamore PT 2023.12 Ultimate | Clarett+ 8Pre | macOS 13.6.3 on a MacBook Pro M1 Max PT 2023.12 | Saffire Pro 40 | Win10 latest, HP Z440 64GB |
#17
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Re: Stereo Dithered Mixer
You can probably talk to Lynn over on his 3DB forum if you are interested.
Greg
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Intel i7 3930K, Gigabyte GA-X79-UP4 (rev 1.0), 32 GB Corsair Vengeance 1600 ram, EVGA Nvidea GT 720 TI video card, a Samsung 850 Pro (256 GB) OS drive, 2 Samsung 850 Pro's (512 GB) in externally mounted drive bays for session and sample storage, Win 10 Pro, PT Ultimate (Native)2019.10, HD Omni, HD I/O 16x16 . |
#18
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Re: Stereo Dithered Mixer
Yeah, I check in there from time to time.
Mmmm. Well, I see was wrong about one thing: hiss from most sources has a Gaussian distribution probability which doesn't give equal chances to whether an error will be rounded up or down. So there's that. Still, if it's loud enough - well above the level that 24-bit dither would be applied - then the quantization errors will only be correlated to the noise. I think. Could be wrong. But if Gaussian - even pink or brown Gaussian - is loud enough to completely bury any TDPF dither that were added, how is the dither going to do anything?
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David J. Finnamore PT 2023.12 Ultimate | Clarett+ 8Pre | macOS 13.6.3 on a MacBook Pro M1 Max PT 2023.12 | Saffire Pro 40 | Win10 latest, HP Z440 64GB |
#19
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Re: Stereo Dithered Mixer
Quote:
http://duc.avid.com/showthread.php?t=5899 + http://duc.avid.com/showthread.php?t=5549 Quote:
G |
#20
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Re: Stereo Dithered Mixer
That makes sense. I love math, actually. Thanks for the other thread links!
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David J. Finnamore PT 2023.12 Ultimate | Clarett+ 8Pre | macOS 13.6.3 on a MacBook Pro M1 Max PT 2023.12 | Saffire Pro 40 | Win10 latest, HP Z440 64GB |
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