Fix the sub2video perf regressions #972

Job	Run time
build_portable_windows / Build Portable FFmpeg (win64)	38m 21s
build_debian / Build FFmpeg (bullseye, amd64)	57m 6s
build_portable_mac / Build Portable FFmpeg (macos-13, x86_64)	50m 14s
build_portable_linux / Build Portable FFmpeg (amd64)	1h 54m 6s
build_debian / Build FFmpeg (bullseye, arm64)	14m 56s
build_portable_mac / Build Portable FFmpeg (macos-14, arm64)	25m 41s
build_portable_windows_clang / Build Portable FFmpeg (CLANG64, win64)	1h 7m 42s
build_portable_linux / Build Portable FFmpeg (arm64)	1h 46m 12s
build_debian / Build FFmpeg (bullseye, armhf)	13m 53s
build_debian / Build FFmpeg (bookworm, amd64)	1h 1m 32s
build_ubuntu / Build FFmpeg (focal, amd64)	57m 29s
build_debian / Build FFmpeg (bookworm, arm64)	14m 40s
build_ubuntu / Build FFmpeg (focal, arm64)	14m 29s
build_debian / Build FFmpeg (bookworm, armhf)	13m 24s
build_ubuntu / Build FFmpeg (focal, armhf)	14m 2s
build_ubuntu / Build FFmpeg (jammy, amd64)	53m 20s
build_ubuntu / Build FFmpeg (jammy, arm64)	15m 18s
build_ubuntu / Build FFmpeg (jammy, armhf)	13m 31s
build_ubuntu / Build FFmpeg (noble, amd64)	1h 5m 54s
build_ubuntu / Build FFmpeg (noble, arm64)	17m 1s
build_ubuntu / Build FFmpeg (noble, armhf)	13m 53s
build_portable_windows / Publish Portable Release	0s
build_portable_mac / Publish Portable Release	0s
build_debian / Publish Release	0s
build_ubuntu / Publish Release	0s
build_portable_windows_clang / Publish Portable Release	0s
build_portable_linux / Publish Portable Release	0s
	14h 2m 44s

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