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Old 12 October 2016, 11:34   #30
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Join Date: Nov 2007
Location: Lyon / France
Age: 45
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Originally Posted by pandy71 View Post
Explain me how 6+8 can give more than 14 in terms of DAC accuracy if you have only 8 bit accuracy at best.
I already explained.
Two 8-bit samples give 65536 combinations. Not all of them are useful but we can get 14bit and more.

Originally Posted by pandy71 View Post
It must very clever trick behind it - explain me this please - i believe lot of people can be interested to understand how it works - also it is a bit contradictory to my knowledge about real life circuits (not simple adding and subtracting in CPU register) as real DAC may have very complex non linearity distortions characteristic that require also nonlinear pre-correction.
The 8+6 that is made isn't simple 8+6 (unless no calibration file is found).
The input is a 16-bit sample. The output is two 8-bit samples, both fetched from a table. You can call that nonlinear pre-correction if you want.
I can't really tell the theory behind this, only that it works fine.

Originally Posted by pandy71 View Post
So once again asking for knowledge - please share knowledge - my engineer knowledge says:
16 bit sample must fit in 14 bits, this produce unavoidable quantization error (2 bits), such error must be processed somehow - worst case scenario is truncation but this lead in unavoidable way to harmonics distortions which are highly correlated with signal so they can be easily perceived - to avoid this type distortion you need to de-correlate quantization distortions and usually it is done by adding TPDF dither (at least 2LSB) to signal before re-quantization, noiseshaping can be used instead or together with dither to improve perceived SNR and perceived system dynamics.
With normal volume levels you don't hear any quantization at all, as the quantization error is weak - 2bit in a 16bit sample is very quiet - and i suspect most of it will be filtered out by the hardware (after all this is just high frequencies).

Have you heard an Amiga playing 14bit ?
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