Multiple subs in mp4 make seeking freeze

Erik Slagter erik at
Mon Jun 13 11:01:38 PDT 2011


> Hi guys,
> I am currently trying to find a nasty problem I have been having with
> gstreamer for ages. Gstreamer is being used in enigma2, a settopbox
> "gui", which uses gstreamer to play any non-transport-stream media. It
> does so by using a playbin2().
> The problem is this: an mp4 file with one (1) subtitle track works like
> a charm. As soon as more are present, problems come. Sometimes the file
> plays until the end, sometimes it freezes. If I select the second
> subtitle track, at least I don't get the subtitles, also sooner or later
> it freezes as well.
> The problem of not getting subs after switching sub track can be worked
> around by seeking to the start of the file and back, as recommended by a
> developer for older versions of gstreamer. Enigma2 uses 0.10.32 though,
> which doesn't seem that old to me?
> But then the freezing is appearing even more. I've done a lot of
> debugging on the enigma2 source code lately and I now can dismiss any
> bugs in that code causing this. It's very simple. Every time I activate
> the second subtitle track ("current-text" = 2), and then do a seek
> (something like this:)
> rv = gst_element_seek_simple(GST_ELEMENT(m_gst_playbin),
> The call doesn't return and the pipeline halts after some time.
> This does *not* happen when subtitle track 1 or no subtitle track is
> selected. The actual seek position doesn't matter, it always freezes.
> Also in the meantime no significant messages are delivered to the app.
> It's just... frozen.
> Is this a known problem, has this been fixed in newer versions? I can't
> find any references to this problem, so I guess not.
> Can somebody try it?
> Here you can find example files: The -x
> part describes how many subtitle tracks are present.
> I also noticed that subtitles of the first subtitle track are delivered,
> even if no subtitle is actually selected, is this is a known problem?
> ("current-text" = -1).
> Thanks for your effort!

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