it seems that "SigmaDelta" is true for natural 8-bit mono files. I mean when a random data is embedded into such a file, SigmaDelta increases.
but the problem is that when we double-embed an already embedded audio file, in most of the cases we observe an increase in SigmaDelta! So how embedded and non-embedded files can be distinguished?
there is a mjor point to which we should pay attention, and that is an embedded file's sigmadelta is lower than 1000 but a non-embedded one is not.
maybe this strategy can be helpful:
1. check SigmaDelta strategy, if Sigmadelta(embedded) <= Sigmadelta(original) then file is not original. 2. if not: check if sigmadelta(original)>1000 then file is original.
3. if none of the aboves: the file should be examined more...but in most cases it's not original.

what's your oppinion??