SMPlayer Support Forum

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Q. How to play YouTube videos at the highest quality and with subtitles

You can play YouTube videos at 1080p or even at 4K resolution with SMPlayer. You only need to make a small change in the SMPlayer configuration. In Preferences -> Network select mpv + youtube-dl in the option Support for video sites. Also be sure mpv is selected as multimedia engine in Preferences -> General.

This modification also makes the YouTube subtitles available in SMPlayer.

Note: Linux users must install youtube-dl.

That enabled 60fps and 1080p however the videos aren't h264 and thus I'm getting no hardware decoding. Is it possible to force h264 only?

That video has a video track at 1080p, 60 fps and h264, however when I try to force mpv to use it, it defaults to the 720p (30 fps) version. I don't know why.