Audio Incorrect dB values in audio mixer

I am currently developing a plug-in that includes measuring audio levels, but my results are always ~0.15 dB to high compared to the test signals. For example, I play an audio file with a sinus wave, 1000 Hz at -23 dbFS, but my plug-in shows -22.85 dB. At first I thought the problem is within my code, but then I noticed that the audio mixer meter (set to peak metering) also shows -22.9 and -22.8 dB (rapidly switching), so it has roughly the same offset.

Does someone know why there is this offset and how to avoid it? I know I could just hard-code the 0.15 dB into my plug-in to get the right values, but I am afraid that this offset changes with different systems (OS and hardware).

I use Unity 2019.1.5f1

 

Can perhaps someone from Unity clarify this?

 

Okay, I think I got this myself. The problem seems to be the Vorbis compression format of the audio clip. As soon as I set it to PCM the dB values are correct.