Once the hls.js timeout fix stopped masking it, the actual segment
request came back with a real 500. Emby's own server log (shared by the
user, not from this app) shows exactly why: ffmpeg's subtitles filter
failing with "Failed to load fontconfig fonts!" inside StartFfMpeg -
a font/fontconfig-cache problem in whatever environment Emby's
transcoder runs in, not anything this app's request could cause.
No code change: this app deliberately forces SubtitleMethod=Encode (see
applyPlaybackOverrides) since it never wires up hls.js's rendition-based
subtitle API - dropping that to dodge the 500 would just bring back the
original "subtitle picked, never shown" bug instead of fixing anything.
Recorded as Round 4 of the player-track-selection saga so this doesn't
get re-investigated from scratch later.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>