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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Re: Y'all missing something important there. posted by macaque on November 16, 2005 at 17:23:49:
Section 2.1 of the page I pointed to way back near the beginning of this thread has example files you can play on your computer soundcard or burn to CD and listen to exaggerated ditherhttp://audio.rightmark.org/lukin/dither/
Starting with a 16/44 “master†the example files are truncated to 8 bits and various dither algorithms are applied
Simple truncation has huge quantization noise modulation – listen for the spitting as the sample fades at the end
Unshaped dither is hissy but the noise isn’t perceptibly modulated by the signal
The best noise shaped dither is not readily audible to me (40+ yr old ears, open back headphones 4’ from computer fan)
With a variety of software such as eac, scilab(does ffts too) you can look at the .wav file, the best sounding noise shaped dither has huge noise, just at freq where I at least can’t hear it
Dither is not masking, quantization is a nonlinear process that does “encode†some signal properties into the added dither – but the math clams you can prevent correlation in 1st and 2nd statistical moments (ave and variance) so the resulting “product†noise isn’t perceptibly modulated by the signal correlation that appears in higher statistical moments
Noise Shaped dither minimizes audibility of inband added noise, having a filter remove the dither noise would be ideal but isn’t the reality with 44.1 data rate
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- Why not just listen, then look… - jcox 20:16:20 11/18/05 (0)
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