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Old 12 October 2016, 10:56   #29
pandy71
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Join Date: Jun 2010
Location: PL
Posts: 1,546
Quote:
Originally Posted by meynaf View Post
I maintain that you can get slightly more than 14 bit with Paula (with real Paula ; not in emulators which are really limited to 14 bit).
Explain me how 6+8 can give more than 14 in terms of DAC accuracy if you
have only 8 bit accuracy at best.

Quote:
Originally Posted by meynaf View Post
Remember that we use two 8-bit DAC for playing single 16-bit sample. If we could shift the volume 8 positions we would get full 16 bit. But we can only shift 6 bits (volume 64 vs volume 1). So in theory this is 14 bit, but the output is nonlinear so we have more combinations than just 16384 ; by reordering them cleverly we get over 14bit accuracy.
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.

Quote:
Originally Posted by meynaf View Post
A good 14-bit routine plays 16-bit samples, not 14-bit samples.
Sure i'm not electronics engineer but i've seen the code and you have not.
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.

Quote:
Originally Posted by paul1981 View Post
16-bit 44.1 kHz - 24-bit 192 KHz is crap, semi-modern D/A converters do a good job of covering this up...a very good job. It's trickery though.
Are you able to provide explanation for this? I'm really surprised to read that 24-bit 192 KHz is crap.

Quote:
Originally Posted by paul1981 View Post
1-bit DAC, are you talking about sdm? Paula doesn't perform any tricks to give a perceived enhanced output, so in this respect it will not sound as good as a CD player even, but the extra bit depth of 14-bit over 8 is very welcome indeed. Cd's were going to be 8-bit originally, heaven forbid...
1 bit is extreme example to illustrate that number of bits may not be so important.
Everything is more complex and trust me - 8 bit may be better than 16 if proper signal processing is applied to it.

Quote:
Originally Posted by paul1981 View Post
Sub-nyquist? I think we're all talking about 44.1 KHz here, which Paula will happily run at in 30KHz screen modes.
Well... Paula may run with increased sample rates but nominal system specification can be considered as sub-Nyquist DAC - to run Paula with increased sample rate you need to increase horizontal frequency rate, not sure if someone tried to do this in software on OCS/ICS (in theory this is possible in similar fashion as fake 60Hz modes only more difficult), so practically increased horizontal frequency require ECS/AGA or you need to start using audio DAC in non-DMA mode (so involve or CPU or/and Copper).

Last edited by pandy71; 12 October 2016 at 11:08.
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