Proper audio resampling should not be identifiable. Of course, the OS mixer probably doesn't do proper (CPU expensive) resampling.
But a quality audio player should account for this and do it's own.
But a quality audio player should account for this and do it's own.
It is an incredible resource to see the quality of the resampling algorithms used by the actual production software likely used in any digital audio workflow.
You will see that while the best are indeed almost 100% transparent, many are not.
your software is among the best, but not pitch black best :)
There is also https://src.hydrogenaudio.org/ (with no IP based restrictions, AFAIK).