Similar to 4c9c4fe8, but for durations. This fixes #7151, where
the report duration and bitrate on a mpegts stream is wildly off
due to the dvb_teletext stream's timings.
Signed-off-by: Aman Gupta <aman@tmm1.net>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>