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Subject: Re: What Is Dithering?

Re: What Is Dithering?

From: Manuel Dejonghe <manuel_at_dejonghe.de>
Date: Fri, 17 Nov 2006 14:35:13 +0100

On 11/17/06, Christopher Woods <christof_at_infinitus.co.uk> wrote:
> In a nutshell, dithering is A Good Thing, as it minimises error in resampled
> or down/upconverted signals, it's used a lot for waveform analysis (and
> audio work, particularly where high quality is sought), I know that
> dithering is definitely one of the things on my to-do-checklist whenever I'm
> doing audio editing in the 24- or 32-bit digital domain when I do my final
> master mixdown for CD audio publishing (which is 16bit). A lot of recording
> studios do all their work at 24- or even 32-bit (but 32bit is fairly
> overkill, 24 is fine) and only at the very last stage do they downconvert
> the final mix to 16-bit, as keeping your audio signals at as high a bitdepth
> as possible will preserve data which is more easily lost through multiple
> generations of signal processing or edits.
>
> In the context of your device, I guess it could be applied like so: if you
> have, say, 24bit audio but your device can only output 16bit due to hardware
> constraints, the firmware will (have to) resample the audio realtime, and
> dithering can improve slightly on the quality. All to do with Nyquist
> frequencies, signal aliasing... It's messy stuff.
>
> And I'm doing a degree on all this! I still don't fully get it, it's bloody
> complicated. I guess a comparable analogy (best I can think of right now)
> would be if you take a large image, and resize it to a smaller size - if you
> have your settings to just go with each pixel's nearest neighbour when you
> shrink the image, you'll get uneven lines, jaggedy edges and it'll look a
> bit poor... Whereas if you set your image program to do bicubic or bilinear
> resizing, it looks at the pixels, their relationship to the ones next to
> them, and 'redraws' the image in a sense, blurring together areas for want
> of a better description, to produce a more aesthetically-pleasing result -
> lines look smoother, colours blend and gradient better...
>
> The Wikipedia article on it is pretty informative:
> http://en.wikipedia.org/wiki/Dithering.

Gee, fine reading, thanks for that one.
I always thought I'd knew what it was, but your "nutshell" put it in
right shapes.

~lImbus
Received on 2006-11-17


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