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Topic: quality loss oft software controlled volume (Read 2531 times) previous topic - next topic
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quality loss oft software controlled volume

What's the theoretical loss of quality if one uses a digital software filter to control the volume (i.e. lowering the volume).

Example:

I'm using a simple software mixer of my operating system with a range of 0% (silence) to 100% (full volume).
The source is a lossless format in 16 bit / 44.1kHz.
What's the loss of quality if the mixer is set to 50% eg.
What do you think is the subjectively perceived loss in such a case? Is it even worth caring about?


Cheers

quality loss oft software controlled volume

Reply #1 –
Worst case, you decrease the signal-to-noise ratio of your playback by the amount you reduce the volume. You lower the program volume and the noise stays at the same level.

Best case is that there is negligible or no effect. If your playback system has 100 dB SNR and your but the signal to noise ratio of your program material or listening environment is 70 dB, you can turn down the digital volume control 15-20 dB before your system performance will measurably affect playback performance.
 

quality loss oft software controlled volume

Reply #2 –
Well...  When you lower the volume (analog or digital) you are "loosing quality" as the quiet sounds and details are pushed below audibility, or pushed down into the noise.  This is natural and you can't avoid it.  The same thing happens if you're listening near the loudspeaker and you walk further away.

If you reduce the volume of a 16-bit file by 50%, the most significant bit will always be zero, and in-effect, you've only got 15 bits.  So yeah it's a lossy process, but the "lost bits" are at very low levels.  (You didn't have fractional-bit information before you lowered the volume, and you don't have any fractional-bit information after lowering the volume...)

Quote
What do you think is the subjectively perceived loss in such a case? Is it even worth caring about?
  No!  You shouldn't worry about it unless you are re-boosting the volume later, and only if you're making big volume changes....  Again, this is the same as analog.  You shouldn't reduce the volume/signal only to re-amplify it later.  (i.e. You shouldn't take a line-level signal, run it through an attenuator and then into a microphone preamp.)