Fix video not being playable on MacOS when encoded with hevc_videotoolbox

[vmzhivetyev]

Problem

Apple QuickTime player on Mac only supports hvc1. Finder's Quick Look feature also uses QuickTime.

As of now a video encoded using hevc_videotoolbox encoder cannot be played on MacOS without using a 3rd party player.

Solution

Force avc1 (instead of default hev1) tag when encoding a video using MacOS-native hardware encoder.