by j7n » Sat May 20, 2017 2:33 pm
If you boost the level extremely, you will reveal noise or other artifacts present in the source audio file (if it is quiet). If the audio file uses full amplitude, and you turn it up further, you get clipping. With amplification by 600%, you throw away about 3 bits. At 100% there is no quality loss.
I have a few quiet test streams, and I see that MPlayer decodes them to low resolution.
MP3 sounds horrible, AC-3 is pretty bad, other formats are tolerable, but not as accurate as they could be due to output limited to 16-bit. The software volume filter is applied prior to reduction of bit depth for output, as it should be. It seems that the internal accuracy of MPlayer and ffmpeg is sacrificed for speed. Where it shows "float" it still sounds worse than in Foobar old versions, for example.