Incorrect duration of ASS subtitles

Important Information

Provide following Information:

• mpv version: git master
• Windows Version: Win11 22H2
• Source of the mpv binary: https://github.com/zhongfly/mpv-winbuild
• If known which version of mpv introduced the problem

Reproduction steps

1. Play videos with the sample subtitle.
2. Seek to 23m50s, continue playing until the end.

Expected behavior

The duration of the sample subtitles is displayed normally, just like vlc.

Actual behavior

The duration of the last subtitle event is incorrect, it always appears on the screen until the end of the video.

https://github.com/mpv-player/mpv/assets/61936050/950ea221-2ec0-4934-8fd4-f6ae222923cc

The problem here is that the last subtitle event in the sample subtitle file has an incorrect duration, and mpv did not process it correctly.

Dialogue: 1,0:23:57.49,0:23:57.45,ed  - jp,,0,0,0,fx,{\an5\\t(0,100,\3c&H000000&)\t(100,200,\3c&HA0FF00&)\t(200,300,\3c&H000000&)\t(300,400,\3c&HA0FF00&)\t(400,500,\3c&H000000&)\t(500,600,\3c&HA0FF00&)\t(600,700,\3c&H000000&)\t(700,800,\3c&HA0FF00&)\t(800,900,\3c&H000000&)\t(900,1000,\3c&HA0FF00&)\t(1000,1100,\3c&H000000&)\t(1100,1200,\3c&HA0FF00&)\t(1200,1300,\3c&H000000&)\t(1300,1400,\3c&HA0FF00&)\t(1400,1500,\3c&H000000&)\t(1500,1600,\3c&HA0FF00&)\t(1600,1700,\3c&H000000&)\t(1700,1800,\3c&HA0FF00&)\t(1800,1900,\3c&H000000&)\t(1900,2000,\3c&HA0FF00&)\t(2000,2100,\3c&H000000&)\t(2100,2200,\3c&HA0FF00&)\t(2200,2300,\3c&H000000&)\t(2300,2400,\3c&HA0FF00&)\t(2400,2500,\3c&H000000&)\t(2500,2600,\3c&HA0FF00&)\t(2600,2700,\3c&H000000&)\t(2700,2800,\3c&HA0FF00&)\t(2800,2900,\3c&H000000&)\t(2900,3000,\3c&HA0FF00&)\t(3000,3100,\3c&H000000&)\t(3100,3200,\3c&HA0FF00&)\t(3200,3300,\3c&H000000&)\t(3300,3400,\3c&HA0FF00&)\t(3400,3500,\3c&H000000&)\t(3500,3600,\3c&HA0FF00&)\t(3600,3700,\3c&H000000&)\t(3700,3800,\3c&HA0FF00&)\t(3800,3900,\3c&H000000&)\t(3900,4000,\3c&HA0FF00&)\t(4000,4100,\3c&H000000&)\t(4100,4200,\3c&HA0FF00&)\t(4200,4300,\3c&H000000&)\t(4300,4400,\3c&HA0FF00&)\t(4400,4500,\3c&H000000&)\t(4500,4600,\3c&HA0FF00&)\t(4600,4700,\3c&H000000&)\t(4700,4800,\3c&HA0FF00&)\t(4800,4900,\3c&H000000&)\t(4900,5000,\3c&HA0FF00&)\t(5000,5100,\3c&H000000&)\t(5100,5200,\3c&HA0FF00&)\t(5200,5300,\3c&H000000&)\t(5300,5400,\3c&HA0FF00&)\t(5400,5500,\3c&H000000&)\t(5500,5600,\3c&HA0FF00&)\t(5600,5700,\3c&H000000&)\bord3\shad2\blur15\be3\pos(820,37)}い

Commit https://github.com/mpv-player/mpv/commit/740b7013ba827ce5a9d48138af5bd2e8f5d54710 introduced handling for subtitles with unknown duration, but it is obvious that this processing method is not correct enough and needs to be fixed.
Maybe we can refer to how it was handled in sd_lavc

Log file

mpv.log

Sample file

[Nekomoe kissaten&VCB-Studio] Mahou Shoujo Site [01][Ma10p_1080p][x265_flac].sc.zip

Start with the supplied ASS sample and the unknown-duration handling introduced in commit 740b7013ba827ce5a9d48138af5bd2e8f5d54710; compare it with the handling referenced in sd_lavc. Reproduce the issue by seeking to 23m50s, then verify that the final subtitle event ends at its intended time instead of remaining visible until the video ends.