I've seen several papers about the double quantization effect, e.g. (https://www.researchgate.net/publication/225180603_Detecting_Doctored_JPEG_Images_Via_DCT_Coefficient_Analysis?ev=srch_pub).

How reliable is this method? How often can you see periods which are an evidence of image resaving? As far as I understood, there are 3*64 different histograms (3 channels with 64 DCT frequencies each). At which histograms should one look first? On how many histograms on average can one see the effect in a general case? Are there many cases (if at all) where one can see periods even though the image was not resaved in any graphics editing program?

Many questions - any answers are highly appreciated.

Conference Paper Detecting doctored JPEG images via DCT coefficient analysis