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Subject: Re: What Is Dithering?

Re: What Is Dithering?

From: Pieter Bos <bos.pieter_at_gmail.com>
Date: Fri, 17 Nov 2006 13:41:53 +0100

"Pieter Bos" <bos.pieter_at_gmail.com> wrote in message
news:ejk788$e13$1_at_sea.gmane.org...
>
> "Christopher Woods" <christof_at_infinitus.co.uk> wrote in message
> news:007801c709fa$c51ffb70$4001a8c0_at_20hz...
>> 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...
>>
>
> This analogy is more like increasing the time-resolution (sample rate)
> than increasing the bit-depth.
>
> Perhaps a better analogy, speaking in terms of images, is exactly the
> same: dithering. If you have only a limited number of colours, you can
> produce more colours by drawing tiny dots of different colours. Our eyes
> will automatically blend the colours, so we see a colour that is not
> actually there but which is made up of a blend of the other colours. This
> is applied for example in computer screens with a limited number of
> colours and in printers - you can see the dots in every photo in every
> newspaper!
>
> You can try this yourself: Get two different colour pencils and draw lots
> of dots on a piece of paper, alternating between both the colours.Make
> some different areas, some with more dots with one colour, others with
> more dots with the other colour. Make sure to draw the dots close
> together. Now look at it from a distance. You will see different colours!
> You can try making a drawing with this by changing the number of dots.
>
> If you have only one pencil available, just make drawings with dots, but
> change the number of dots in the same area (eg. completely filled, half
> filled...).
>
> In audio, the concept works almost the same. Think of the bit-depth of the
> audio (16 bit...) as the number of available colours. If you want to match
> a value that is not there, you can add some rapidly changing values close
> to the value you want to match to gain a slightly better quality audio and
> a bigger dynamic range. Now, you're performing dithering!
>
> Pieter

Oh, i should add: in the case of an mp3 player it will slightly increase
audio quality, but most likely you will be unable to hear it, unless you
listen to music with quite soft parts (classical music, for example). It'll
probably cost very slightly more battery, so you can safely disable it
unless you can actually hear the quality difference.

Pieter
Received on 2006-11-17


Page was last modified "Jan 10 2012" The Rockbox Crew
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