Fixes ticket 9086.
Since early 2021, some of YouTube's VP9 encodes have non-monotonous DTS.
This makes ffmpeg fatally fail when trying to copy or encode the V9 video.
ffmpeg already includes functionality to correct this, however it was
disabled without explanation for VP9 stream copies in
2e6636
in.com/raw/GWkrCu5w
>From 0eb57f3746008dc04d86690d97caa1b579d3e215 Mon Sep 17 00:00:00 2001
From: Danny Wu
Date: Wed, 12 May 2021 08:51:13 -0400
Subject: [PATCH] fftools/ffmpeg: Restore DTS correction for VP9 copies
Fixes ticket 9086.
Since early 2021, some of YouTube's VP9 encodes have no
