Crash on ASS files with embedded [Fonts] section (regression in v0.41.0)

[bruuhim]

Description

MPV crashes (segfault/closes immediately) when loading an ASS subtitle file that contains embedded fonts via the [Fonts] section. The crash happens on file load, before any video plays.

The embedded fonts are valid TrueType files (confirmed by decoding the base64 and validating with fonttools). Removing the entire [Fonts] section from the ASS file resolves the crash completely.

Steps to Reproduce

1. Load any ASS file with embedded fonts in the [Fonts] section (multiple font entries, 7+ fonts)
2. Run: mpv --sub-file=file.ass video.mp4
3. MPV crashes immediately on load

Regression

• CRASHES: v0.41.0-718-g1d82932cc (built Jun 4 2026) - Windows 11
• WORKS: v0.40.0-460-g748260893 (built Nov 17 2025) - Windows 11

This is a regression - the same file works on v0.40.0 but crashes on v0.41.0.

Environment

• OS: Windows 11
• MPV: v0.41.0-718-g1d82932cc (built Jun 4 2026)
• libplacebo: v7.365.0
• FFmpeg: N-124795-gc27a3b12e
• GPU: OpenGL (vo=gpu, gpu-api=opengl)

Investigation

The ASS file has 8 embedded fonts (all valid TrueType, confirmed by decoding Aegisub's base64 encoding and validating with fonttools). Re-encoding the fonts cleanly (removing duplicates, proper line-wrapping) did NOT fix the crash. This rules out font corruption - it is a libass parsing/handling regression.

Workaround

Strip the [Fonts] section from the ASS file (subtitles work without embedded fonts if system fonts are available).

[Headcrabed]

Create issue by using template, don't do such.

[arch1t3cht]

I cannot reproduce the crash with your instructions. Please upload a concrete reproducing sample file.

[bruuhim]

UPDATE: Resolved — shinchiro build-specific issue, not an mpv bug.

Tested with the official GitHub Actions build (v0.41.0-dev-gc75b8d2cc) — no crash. The crash only occurs with the shinchiro Windows build. See #18190 for details.

[bruuhim]

Resolved - this is a shinchiro build-specific issue, not an mpv regression. The official GitHub Actions build works fine. See #18190 for details.