Question about subs sync

[colpoz]

Hi all!

Firstly, excuse me for my bad english..

I'm trying to find the better way to get a perfect .mkv compared to the original film in blu-ray... and when I say perfect I do mean PERFECT!!

I have a question about sync of subs.
I've tried to compare the PGS subs extracted from mkv created using makemkv and other ones extracted using eac3to.
Analyzing the singles subtitles through BDSup2sub, I've noticed that there are (almost always) differences in the "timings" (I'm referring to the start time and the end time of subs visualization).

For example, the following are the starting time of the first 3 subs extracted from Pirates of the Caribbean BR using MakeMKV:

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#> 1 (00:00:27.578)
#> 2 (00:00:42.634)
#> 3 (00:00:45.721)

and instead the following were extracted using eac3to:

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#> 1 (00:00:27.569)
#> 2 (00:00:42.626)
#> 3 (00:00:45.712)

As you seen, there is a constant 8-9 ms gap.
This gap is visible when playing mkv frame-by-frame, the MakeMKV subs appears one frame later than eac3to subs.

I know that it is a very small difference.. but which one is more correct?

ps. I've also noticed that eac3to timing appears to be an exact multiple of one frame lenght (at 23,796fps one frame is 41,7083ms long):

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00:00:27.569 = 27569ms, and 27569 / 41,7083 = 660,995 --> ~661th frame

while MakeMKV timigs are not exact multiples.