it seems to be seeking on segment boundaries only.
Of course, if I put -ss after the input '-i' I seek accurately but
it's an output parameter now so it takes much longer since it's
decoding all the frames (also doesn't work with multiple input maps).
And according to 'https://trac.ffmpeg.org/wiki/Seeking' input seeking
should be accurate
Is this a bug or I am missing a parameter?
(BTW, I posted this same question in Nov 2016 without a valid answer.
If no one can answer this time, I'll open a bug)