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Into which bit should noise be added in order to dither 32bit file to
amiti
post Oct 6 2012, 22:54
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When adding noise to audio data in order to dither it into lower bit depth, should the noise be added to higher bit than the desired outcome bit depth? For example when 24bit data is meant to be dithered into 16 bit , the white noise should be added between the 17th to the 24th bits of the original file?

I saw this plugin for foobar : foo_dsp_noise. With this plugin foobar can add TPDF noise up into the 24th bit but not higher. Does this mean it is usable only for dithering to 16bit and not to 24bit output?

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2Bdecided
post Oct 8 2012, 17:39
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You add as many bits of dither as you are removing bits from the signal. So 16>8, 24>16 and 32>24 all require dither noise added to the 8LSBs, because you are chopping 8-bits off. 32>8 would require 24-bits of dither!

If you add an 8-bit pseudo random number generator, you'll get flat rectangular dither. Add two (or add one then subtract another) and you'll get flat triangular dither (which, because you're adding two 8-bit numbers, will often fill the 9 LSBs).

Of course by adding a number to the 8 LSBs, you may change the value of any or all bits. Just like adding 1 to 899 changes all the decimal numbers, even though it is a single digit.

Cheers,
David.

This post has been edited by 2Bdecided: Oct 8 2012, 17:40
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krabapple
post Oct 27 2012, 20:26
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QUOTE (2Bdecided @ Oct 8 2012, 12:39) *
You add as many bits of dither as you are removing bits from the signal. So 16>8, 24>16 and 32>24 all require dither noise added to the 8LSBs, because you are chopping 8-bits off. 32>8 would require 24-bits of dither!


Is truncation from 32 to 24 bits generally thought to be audible?

This post has been edited by krabapple: Oct 27 2012, 20:27
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