Oddly Muxed MKV won't Play #64
Description
I have an oddly muxed mkv that will not play in the official Jellyfin Android TV app using libass-android v.0.4.0, but will play and render subtitles in vlc, mpv and Jellyfin Android TV when forced to transcode via ffmpeg. When I try to play the mkv, ExoPlayer just remains a black screen. Upon checking the Jellyfin server logs, it seems playback is started but then instantly stops, then starts, then instantly stops. This continues until I back out of ExoPlayer in the client.
I previously tested this same mkv under v0.4.0-alpha01. It would take ~10 seconds to load in ExoPlayer, then Exoplayer would behave as though it was playing with the time bar advancing, but the screen was black without audio, After if I scrubbed forward or backward in the video, video, audio, and ASS subtitles would begin playing fine.
If i remux the mkv, keeping all tracks and fonts, in MKVToolNix, it play just fine on Jellyfin Android TV app using android lib-ass v.0.4.0. Unfortunately due to the contents of the mkv, I cannot upload it to GitHub. However I have provided it directly to the libass-android developers. However below is the results of mkvinfo on the mkv. Font attachments are listed first, so maybe it is an example of #24 ?
+ EBML head
|+ EBML version: 1
|+ EBML read version: 1
|+ Maximum EBML ID length: 4
|+ Maximum EBML size length: 8
|+ Document type: matroska
|+ Document type version: 4
|+ Document type read version: 2
+ Segment: size 764021203
|+ Seek head (subentries will be skipped)
|+ EBML void: size 45
|+ Segment information
| + Timestamp scale: 1000000
| + Multiplexing application: Lavf61.7.100
| + Writing application: HandBrake 1.10.2 2025090600
| + Segment UID: 0x00 0xab 0x5e 0xcd 0xd0 0x95 0x63 0xfd 0x08 0x47 0x18 0xad 0x7a 0x80 0x9c 0xf3
| + Date: 2025-12-06 23:25:08 UTC
| + Duration: 00:23:51.600000000
|+ EBML void: size 23944
|+ Attachments
| + Attached
| + File name: Adobe Arabic.ttf
| + MIME type: application/x-truetype-font
| + File data: size 639064
| + File UID: 10194682767914786793
| + Attached
| + File name: Arial.ttf
| + MIME type: application/x-truetype-font
| + File data: size 1036584
| + File UID: 4983637153085138619
| + Attached
| + File name: Comic Sans MS.ttf
| + MIME type: application/x-truetype-font
| + File data: size 260780
| + File UID: 17160943384340969397
| + Attached
| + File name: NotoSansThai-Bold.ttf
| + MIME type: application/x-truetype-font
| + File data: size 47480
| + File UID: 12236574870431856677
| + Attached
| + File name: Courier New.ttf
| + MIME type: application/x-truetype-font
| + File data: size 709600
| + File UID: 13117264485837572108
| + Attached
| + File name: DejaVu LGC Sans Mono.ttf
| + MIME type: application/x-truetype-font
| + File data: size 335068
| + File UID: 5679076098779715146
| + Attached
| + File name: Tahoma.ttf
| + MIME type: application/x-truetype-font
| + File data: size 310752
| + File UID: 15774701854306210447
| + Attached
| + File name: Times New Roman.ttf
| + MIME type: application/x-truetype-font
| + File data: size 68372
| + File UID: 7330604309854406032
| + Attached
| + File name: trebuc.ttf
| + MIME type: application/x-truetype-font
| + File data: size 254396
| + File UID: 4535829930236771672
| + Attached
| + File name: trebucit.ttf
| + MIME type: application/x-truetype-font
| + File data: size 252224
| + File UID: 13168963940546708504
| + Attached
| + File name: Verdana.ttf
| + MIME type: application/x-truetype-font
| + File data: size 149752
| + File UID: 868186613095368489
|+ Tags
| + Tag
| + Targets
| + Simple
| + Name: ENCODER
| + String: Lavf61.7.100
| + Tag
| + Targets
| + Track UID: 5225109363916210190
| + Simple
| + Name: DURATION
| + String: 00:23:50.012000000
| + Tag
| + Targets
| + Track UID: 8620017840777853092
| + Simple
| + Name: DURATION
| + String: 00:23:50.061000000
| + Tag
| + Targets
| + Track UID: 11415095522679811444
| + Simple
| + Name: DURATION
| + String: 00:23:50.061000000
| + Tag
| + Targets
| + Track UID: 16751839982319122323
| + Simple
| + Name: DURATION
| + String: 00:23:50.010000000
| + Tag
| + Targets
| + Track UID: 8256426983831499691
| + Simple
| + Name: DURATION
| + String: 00:23:50.010000000
| + Tag
| + Targets
| + Track UID: 2839041102447251620
| + Simple
| + Name: DURATION
| + String: 00:23:50.010000000
| + Tag
| + Targets
| + Track UID: 11207325616364365580
| + Simple
| + Name: DURATION
| + String: 00:23:49.990000000
| + Tag
| + Targets
| + Track UID: 7246396533440039254
| + Simple
| + Name: DURATION
| + String: 00:23:49.950000000
| + Tag
| + Targets
| + Track UID: 5988844275834955331
| + Simple
| + Name: DURATION
| + String: 00:23:49.990000000
| + Tag
| + Targets
| + Track UID: 15922255043847189833
| + Simple
| + Name: DURATION
| + String: 00:23:50.030000000
| + Tag
| + Targets
| + Track UID: 15065749791456124078
| + Simple
| + Name: DURATION
| + String: 00:23:50.300000000
| + Tag
| + Targets
| + Track UID: 12529485237601311234
| + Simple
| + Name: DURATION
| + String: 00:23:51.600000000
| + Tag
| + Targets
| + Track UID: 7317159775326770146
| + Simple
| + Name: DURATION
| + String: 00:23:51.600000000
|+ Cluster