Fix ffmpeg warnings as of 3.4.1#1

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cosmin wants to merge 2 commits intoFastSociety:masterfrom

cosmin:fix-ffmpeg-3.4-warnings

Commits on Jun 9, 2017

updated references to work with ffmpeg 3.3
cosmin
committed

Commits on Feb 3, 2018

fix all warnings under ffmpeg 3.4.1 by moving away from deprecated APIs to more modern alternatives
cosmin
committed