Segment starts on the seek timeline are derived from EXTINF durations,
so the first keyframe of the target segment can have a slightly lower
DTS than the snapped seek position, in which case the packet discard
loop would skip it and resume playback one segment late. Make sure we
start at the very beginning of the stream in this case.
Signed-off-by: Kacper Michajłow <kasper93@gmail.com>
848fb754dd