Mpeg2 Codec

I shoot HDV which is compressed with the mpeg2 codec. It works fine. I am, however, under the impression that there are several "manufacturers" of such codecs and each differs some. It seems, I think, that a manufacturer has the option of including a de-blocking filter. Since de-blocking filters are only used after decoding, their presence or absence does not affect the decoding process.

Can anyone tell me exactly which mpeg2 manufacturer/version after effects uses?

Even at scale 1600 where every pixel is clearly visible, I do not see any identifiable compression caused blockiness in my footage. I'm thinking the after effects codec does employ a de-blocking filter.

Thanks