First encountered subtitle not displayed in some .MKV files
The first encountered subtitle of some .MKV files is not displayed.
System: macOS Sierra 10.12.4
Steps to reproduce:
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Download a macOS VLC nightly starting from version 3.0.0-!20170405-0445 (revision 2.2.0-git-12020-gc6ed150a; previous version 3.0.0-!20170404-0445-git / revision 2.2.0-git-12009-g6fc45a5b worked; also tested with the latest nightly at the time of writing this, version 3.0.0-!20170421-0445-git / revision 2.2.0-git-12282-g1e9030d2).
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Download the test5.mkv file of the Matroska Test Suite.[1]
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Run the downloaded VLC and start test5.mkv playback.
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 subtitles will be displayed normally.
Observations:
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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 re-enabling them) makes the behaviour reappear. Resetting the VLC profile changes nothing.
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Not all .MKV files seem to exhibit this behaviour. The subtitle type does not seem to determine whether it happens or not (the example file uses subst subtitles; some files with ssa subtitles show it but others don't).
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The behaviour is also reproducible with Windows nightlies of the same time frame (tested on a Windows 7 x86-64 VirtualBox guest, macOS host).
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The behaviour is not reproducible on an Ubuntu 16.04 x86-64 VirtualBox guest when played with the current snap build (revision 2.2.0-git-11793-g508452ae).
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Extremely limited testing of other containers has not shown the described behaviour.
[1] Matroska Test Suite - Wave 1: https://www.matroska.org/downloads/test_w1.html