testsrc

Forced subtitles that aren't the default track

edge/mkv-forced-not-default-subs.mkvMatroskaEdge case

Matroska with forced subtitles, the kind that translate signs and foreign dialogue, not marked as the default track.

How it should play

[sign reads: EXIT]

What a broken player shows

An illustration of the symptom, not a frame from the file.

What goes wrong

Forced subtitles should show anyway; many players show none.

The file

Container
Matroska, 6.021 s
Size
5.5 MB
Video
H.264, 1920x1080, 30 fps
Audio
AAC, stereo, 48,000 Hz
Expected
plays correctly in any player

How it was verified

Built by the testsrc generator (gen v0.2) and verified with FFmpeg 7.1.5-0+deb13u1 and GStreamer 1.26.2 in snapshot 2026-11-02, before it was published: the file has the property this page describes, and decoding it gives the expected result.

With a token: the file, how exactly it was built, the full fact sheet, and the expected result the checker judges a player against.

Use it

# the public facts
curl https://testsrc.com/v1/cases/edge/mkv-forced-not-default-subs.mkv

# the full fact sheet and the file, with your token
curl -H "Authorization: Bearer $TESTSRC_TOKEN" \
  https://testsrc.com/v1/cases/edge/mkv-forced-not-default-subs.mkv/facts
curl -H "Authorization: Bearer $TESTSRC_TOKEN" -o mkv-forced-not-default-subs.mkv \
  https://testsrc.com/v1/files/edge/mkv-forced-not-default-subs.mkv

# play it through your player and check what it showed
testsrc run --player libvlc edge/mkv-forced-not-default-subs.mkv

See the API reference for tokens, quotas and snapshots.

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More on subtitles

2 more cases on this with a token.