Missing first subtitle in some .MKV files since VLC nightly version 3.0.0-20170405-0445

[gonhidi]

Hi,

I am experiencing the following behaviour: since version 3.0.0-20170405-0445 of the macOS VLC nightlies the first encountered subtitle of some .MKV files is not displayed.

Steps to reproduce:

1. Download a VLC nightly starting from version 3.0.0-20170405-0445 (also tested with the latest nightly at the time of writing this, version 3.0.0-20170418-0445)
2. Download the Matroska Test Suite - Wave 1
3. Start playback of test5.mkv

Expected results: three seconds into the video the first subtitle should appear, reading “...the colossus of Rhodes!”.

Actual results: the first subtitle to appear is the second one, five seconds into the video, reading “No!”.

Workaround: once the behaviour is triggered, skip back and the subtitle will be displayed normally.

Observations: Skipping ahead makes the behaviour trigger at a later point (e.g. jumping 40 seconds into test5.mkv, the subtitle at second 41 is not displayed). Changing subtitle tracks (or disabling them and then reenabling them) makes the behaviour reappear. Resetting the VLC profile changes nothing. Not all .MKV files seem to exhibit this behaviour. Limited testing of other containers has not shown the described behaviour.

Operating system: macOS Sierra 10.12.4.

Cheers.

[gonhidi]

It also happens on Windows but apparently not on Ubuntu. I have reported the behaviour in ticket 18245.