Performance of complex ASS/SSA subtitles has regressed in VLC 4.0

The performance of complex ASS/SSA subtitles has regressed in 4.0. Some subtitles cause lag/freezes in 4.0 yet do not cause problems in 3.0.12. CPU usage is higher in 4.0.

OS: Windows 10 Build 19042
VLC version: vlc-4.0.0-dev-win64-c21bf106
Hardware: Intel i5-10210U, Intel integrated graphics
How to reproduce: open video file, navigate to a segment with complex subtitles
Sample file: test2.mkv. On my system, on VLC 4.0, this file hangs for two seconds when the full-screen subtitles start moving. There is no such problem in 3.0.12.

Logs: https://pastebin.com/raw/eKnRcizJ

Edited Apr 01, 2021 by motbob

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