Diagnose a subtitle switch with an HLS fixture
Use a known cue and a deliberate silent interval to distinguish subtitle delivery from what the player renders.
A player lists Spanish subtitles, but after switching from English the viewer still sees English—or nothing at all. A playlist can advertise both languages without proving either one rendered. JoesProxy’s Multilingual Captions fixture gives the player identifiable WebVTT cues and a known gap, so you can tell a missed switch from intentional silence.
Start a stream with a known answer
- Connect your test player and check it can load a known title before changing its source. In fixture profiles, look for Multilingual Captions (
multilingual-text-vod-v1). Use static VOD for this comparison so seeking returns you to the same cue. If the profile isn’t available, don’t substitute a different stream and expect these timings. - Select the profile and start the fixture through the reviewed start flow. Check fixture status. Load its playlist in your test player, or use a narrowly scoped fixture redirect for your app’s test stream. Verify that the player requested the fixture’s master playlist; a running server alone isn’t playback.
- In the player’s subtitle menu, select ordinary English, not English SDH or forced-only. Play through 3.5–5.5 seconds and note the visible language and cue identifier. The fixture’s CUE-002 spans a segment boundary. Use the player’s media time, not wall-clock time.
- Switch to ordinary Spanish, seek back, and play through that same interval. Compare the visible cue with the English run. Then play through 8–12 seconds: the fixture deliberately has no cues there. Silence in that interval is not a failure.
Read the result
| What happened | What it tells you |
|---|---|
| The master playlist advertises Spanish, but the player doesn’t list it. | The option was declared. Check the player’s language and track-role handling; display labels may be localized. |
| Spanish text segments were requested, but the English cue remained visible. | Requests may include prefetch. Record the selected track and visible cue at the same media time; a successful transfer doesn’t prove selection or rendering. |
| The cue changed to Spanish at the known interval, then disappeared during the gap. | The player showed the expected result for this switch and interval. It doesn’t establish that every subtitle role works. |
Restore ordinary playback
Turn regular subtitles off and note any forced-track preference separately. Remove the test redirect if you created one, stop the fixture, and reopen the original title. Verify a fresh request to its ordinary source. For rewind or audio-switch failures instead, use the live DVR investigation.