level matching when comparing lossy to lossless Options

[krabapple]

I probably should have had this settled in my mind long ago, but -- how necessary is it to level match when you are comparing a lossless track, to its mp3 counterpart?

By way of investigation, I compared foobar2k's reported replaygain and track peak values for the same track encoded (LAME 3.98) as V2 (195kbps VBR) and at 320 kbps CBR

lossless:
Track gain -1.08
Track Peak 0.938171

195kbps VBR:
+0.11
0.954459

320kbps CBR:
+.10
0.934477

The track peak differences are negligable, but whence comes the >1db difference in RPG gain of lossless vs. lossy? Does this mean that one should level match according to those RPG values when doing an ABX?

This post has been edited by krabapple: Feb 7 2013, 19:42

[Garf]

If they're encoded from the same source I see no reason to level match, *if* the encoder is not intentionally changing the volume. I understand LAME does this at least in some ABR modes to lower the amount of clipping.

1dB of ReplayGain difference between lossy and lossless is surprising. The ReplayGain calculation isn't perfect of course, but that's more than I'd have expected. Are you sure the same ReplayGain *algorithm* was used in both cases? (original ReplayGain vs R128?)