hlsdemux: issue if target-duration is different than segment-duration

[Loris]

Hi,

It seems that hlsdemux uses the target duration tag to compute when
the next segment should be fetched [0].

This creates an issue when the segment duration is actually lower;
e.g.: most HLS streams from youtube have a target duration of 7 while
each sample is 5.4 sec. The consequence is that sooner or later the
pipeline will block having scheduled the fetching of the next segment
after the previous has already been played [1].

Any reason why the hls demuxer doesn't use the segment duration
instead? It would seem to make more sense, wouldn't it? BTW, this is
what FFMPEG seems to be doing (they don't have the issue) [2].

Thanks,

Loris

[0]: http://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/ext/hls/gsthlsdemux.c#n1171
[1]: http://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/ext/hls/gsthlsdemux.c#n854
[2]: https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/hls.c#L411