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32bit output into 24bit capable soundcard. How bitdepth is converted i
amiti
post Feb 6 2013, 18:10
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When streaming an audio data of 32bit to a 24bit capable soundcard via ASIO, how does the hardware/drivers handle it? Are the excess bits truncated or dithered?

(I use ESI Juli@ souncard)
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amiti
post Feb 12 2013, 14:28
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QUOTE (saratoga @ Feb 12 2013, 05:57) *
QUOTE (amiti @ Feb 11 2013, 20:57) *
Thanks for all the help and information.

QUOTE (IgorC @ Feb 6 2013, 20:03) *
http://en.wikipedia.org/wiki/Digital-to-analog_converter

QUOTE
Noise is ultimately limited by the thermal noise generated by passive components such as resistors. For audio applications and in room temperatures, such noise is usually a little less than 1 μV (microvolt) of white noise. This limits performance to less than 20~21 bits even in 24-bit DACs.


Theoretically then , would it be best to dither audio stream to 20-21 bits , depending on the noise floor of the specific audio hardware?


If you are limited by thermal noise, adding more noise doesn't do anything except make the signal more noisy.


If thermal noise of hardware masks low level data from , let's say, the 21th bit and higher, digital dither could add noise at 20th bit and rescue some micro-detail before it is masked and lost. Isn't this correct?

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Arnold B. Kruege...
post Feb 12 2013, 15:41
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QUOTE (amiti @ Feb 12 2013, 08:28) *
QUOTE (saratoga @ Feb 12 2013, 05:57) *
QUOTE (amiti @ Feb 11 2013, 20:57) *
Thanks for all the help and information.

QUOTE (IgorC @ Feb 6 2013, 20:03) *
http://en.wikipedia.org/wiki/Digital-to-analog_converter

QUOTE
Noise is ultimately limited by the thermal noise generated by passive components such as resistors. For audio applications and in room temperatures, such noise is usually a little less than 1 μV (microvolt) of white noise. This limits performance to less than 20~21 bits even in 24-bit DACs.


Theoretically then , would it be best to dither audio stream to 20-21 bits , depending on the noise floor of the specific audio hardware?


If you are limited by thermal noise, adding more noise doesn't do anything except make the signal more noisy.


If thermal noise of hardware masks low level data from , let's say, the 21th bit and higher, digital dither could add noise at 20th bit and rescue some micro-detail before it is masked and lost. Isn't this correct?



This is a moot conversation because AFAIK there are no real-world recordings with a noise floor that is even 16 bits down. Typical is around 12 bits, and SOTA is 14 bits.

Thermal and acoustical noise do a fine job of dithering, they just need to be a bit (figuratively) larger than optimally shaped TPDF dither.

The worst case program material for bit reduction is digital black. You always scale your dither to deal with just that. IOW about 1 LSB at the reduced word length.

There is a line of thought that goes like this - I've got 24 bit data but I'm worried that it is going to be converted to 16 bits without dither so I'll add the right amount of dither to cover that eventuality. This may sound stupid but in the real world it does no harm because the noise floor of the program material is always even worse than that!
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Posts in this topic
- amiti   32bit output into 24bit capable soundcard. How bitdepth is converted i   Feb 6 2013, 18:10
- - IgorC   http://en.wikipedia.org/wiki/Digital-to-analog_con...   Feb 6 2013, 19:03
|- - db1989   QUOTE (IgorC @ Feb 6 2013, 18:03) http://...   Feb 6 2013, 19:07
|- - pdq   QUOTE (db1989 @ Feb 6 2013, 13:07) QUOTE ...   Feb 6 2013, 19:57
- - pdq   Do you know if the 32 bit data is integer or float...   Feb 6 2013, 19:03
- - benski   >> 8   Feb 6 2013, 19:29
- - db1989   QUOTE (pdq @ Feb 6 2013, 18:57) I think t...   Feb 6 2013, 20:22
- - DVDdoug   I suppose the details are up to the programmer, bu...   Feb 6 2013, 21:02
|- - pdq   QUOTE (DVDdoug @ Feb 6 2013, 15:02) With ...   Feb 6 2013, 21:43
|- - DVDdoug   QUOTE (pdq @ Feb 6 2013, 12:43) QUOTE (DV...   Feb 6 2013, 23:53
- - phofman   QUOTE (amiti @ Feb 6 2013, 19:10) When st...   Feb 6 2013, 23:16
- - Arnold B. Krueger   QUOTE (amiti @ Feb 6 2013, 12:10) When st...   Feb 7 2013, 12:18
- - 2Bdecided   See related thread... http://www.hydrogenaudio.org...   Feb 7 2013, 13:00
- - nu774   Simple right shift results in tiny negative DC off...   Feb 7 2013, 13:25
- - amiti   Thanks for all the help and information. QUOTE (I...   Feb 12 2013, 02:57
|- - saratoga   QUOTE (amiti @ Feb 11 2013, 20:57) Thanks...   Feb 12 2013, 04:57
- - phofman   I guess that is why dither is recommended for deci...   Feb 12 2013, 10:16
- - amiti   QUOTE (saratoga @ Feb 12 2013, 05:57) QUO...   Feb 12 2013, 14:28
|- - Arnold B. Krueger   QUOTE (amiti @ Feb 12 2013, 08:28) QUOTE ...   Feb 12 2013, 15:41
- - pdq   I'm afraid that you are completely missing the...   Feb 12 2013, 15:34


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