Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion. Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules. |
|
13th November 2015, 22:05 | #1 | Link | |
Registered User
Join Date: Feb 2002
Location: San Jose, California
Posts: 4,425
|
Practical Effects of Audio Bit Depth?
This is a question triggered by a post in the eac3to thread but further discussion of it would be off-topic there.
Quote:
1111111111111111, means exactly the same thing as 111111111111111100000000 in a digital integer format. A DAC would give exactly the same output with either input. A DAC effectively pads any input bit depth below its bit depth with zeros. I suppose if you understand the ADC very well 16-bit or 24-bit with the 8 LSBs as 0 are different, by a tiny amount. If 24-bit represents 0 to 1, the 16 MSBs represent 0 to 0.99998480 (an error of 0.00152% compared to a 16-bit ADC). However, if you know the ADC used you don't care what the current format is. This means the ADC and DAC both need to use the same bit depth to avoid quantization errors but truncating to 16 bit or using 24 bits with 8 trailing zeros would both give identical and correct output when using the same DAC. The storage bit depth has no effect on the quantization error at all, only the DAC bit depth compared to the ADC bit depth matters. Truncating 24-bit with 8 zeros in the LSBs to 16-bit would not cause any additional error, even thinking mathematically, during audio playback.
__________________
madVR options explained |
|
13th November 2015, 22:40 | #3 | Link |
Retried Guesser
Join Date: Jun 2012
Posts: 1,373
|
No, a DAC adds a small amount of noise, called Dither aka Noise Shaping. More dither is needed for a lower-precision digital format. Increasing "precision" by adding zeros fools the DAC into not adding enough dither, which may result in digital harshness on the output (albeit at a very low level). Decreasing precision by truncating, without dither, has the same problem.
http://www.digido.com/articles-and-d...16-dither.html https://en.wikipedia.org/wiki/Dither#Digital_audio |
14th November 2015, 00:00 | #4 | Link | ||
Registered User
Join Date: Feb 2002
Location: San Jose, California
Posts: 4,425
|
Quote:
I am sure there is no real 24-bit audio where all LSBs are 0, it must be 16-bit padded to 24, but if there was? Quote:
__________________
madVR options explained |
||
23rd November 2015, 13:25 | #5 | Link | ||
Registered User
Join Date: Mar 2006
Posts: 1,049
|
Quote:
Dither and/or Noise Shaping are usually added at post processing stage, dither is sometimes added to improve overall Delta Sigma DAC stability (usually important for 1 bit DS, usually not so important for multibit DS DAC). 16 bit to 24 bit is equal to multiplication by known number and it is fully lossless and reversible - more important is that usually 16 bit data is anyway converted for more bits to perform processing - classical example are lowpass filters where 16 data are multiplied by for example 12 bit coefficient and as such result is 28 bit new sample value. Nowadays 56 and more bits for audio is not unusual especially in IIR filters (which are more common in consumer audio than FIR filters). Quote:
And this is clear operation from mathematical perspective for this - multiplying by integer value ie shifting bits (8 bits give us 256). DAC conversion is something else than quantization error processing (dithering and/or noise shaping). And dither level for TPDF is 2LSB - rectangular dither can be 1LSB but it is insufficient from signal perspective - usually instead TPDF a HP TPDF is used. Last edited by pandy; 23rd November 2015 at 13:33. |
||
14th November 2015, 02:02 | #6 | Link | |
Retried Guesser
Join Date: Jun 2012
Posts: 1,373
|
Quote:
EDIT After re-reading the question, I'm not so sure. I don't know how a given 24-bit DAC will handle 16-bit data. Would have to look at the spec sheet. Last edited by raffriff42; 14th November 2015 at 05:03. |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|