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Question about dither


Mayuri
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How exactly is dither applied? I mean, say we have a 24 bit 48khz file, it's resampled to, say 192khz, but my device only supports 16 bit output, and dither is turned on.. Is dither (the noise) added before or after it's downsampled to 16 bit by android? And is there any difference? When is it supposed to be added?

P.s. I've done a lot of reading about dither, and still feel like I only understand 50% of what it actually is..

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  • 2 weeks later...
On 1/15/2021 at 12:38 AM, Mayuri said:

How exactly is dither applied? I mean, say we have a 24 bit 48khz file, it's resampled to, say 192khz, but my device only supports 16 bit output, and dither is turned on.. Is dither (the noise) added before or after it's downsampled to 16 bit by android? And is there any difference? When is it supposed to be added?

If it were added after the last 8 bits had been cut then it wouldn't make sense : damage done and an additional damage heaped on top of that. So the dither-noise is added during the truncation or before it. See the wikipedia article https://en.wikipedia.org/wiki/Dither

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This leads to the dither solution. Rather than predictably rounding up or down in a repeating pattern, it is possible to round up or down in a random pattern. [...] This noise is less offensive to the ear than the determinable distortion that other solutions would produce.

 

Edited by RiedRied
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Let's say, you have a 24 bit audio file, but your audio processing system supports only 16bit output. So it would just compress the output down to 16bit. Unfortunately this resolution change affects audio quality (adds more noise, audio artifacts), so to make the audio sound better in low resolution, additional noise (dither) is applied. Dither tries to neutralize audio artifacts/noise caused by downsampling aka compression.

 

Now if you have a CD quality music file (16 bit), it's very much possible that dither is already added to the file. So enabling dither in Poweramp just adds more noise to the audio file, which can make the audio sound bad. 

 

At least that's how I understand it. You could try reading https://theproaudiofiles.com/dither/

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10 hours ago, Someguyonline said:

Now if you have a CD quality music file (16 bit), it's very much possible that dither is already added to the file. So enabling dither in Poweramp just adds more noise to the audio file, which can make the audio sound bad.

That's correct if you don't do any DSP ( eq, reverb, stereox etc ). But if you do any DSP then Poweramp will calculate with 32 bits and the numbers will change. And these numbers then will not have all zeros in bit 17 to 32. If then Poweramp's output gets truncated to 16 bits when it is transferred to the DAC, then dither will make sense here too. Or looking for a high-res-output-setting that accepts 24 bit or 32 bit.

Edited by RiedRied
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