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Subject: RE: What Is Dithering?

RE: What Is Dithering?

From: Christopher Woods <christof_at_infinitus.co.uk>
Date: Fri, 17 Nov 2006 03:45:01 -0000

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.

> -----Original Message-----
> From: Rich De Steno [mailto:ironrock_at_verizon.net]
> Sent: 17 November 2006 01:44
> To: rockbox_at_cool.haxx.se
> Subject: What Is Dithering?
>
> The Sound Settings menu has a "dithering" option, yes or no.
> What effect does this have?
>
>
>
Received on 2006-11-17


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