- dts was not set earlier, although for WebM, we could assume that
dts is the same as pts.
- Calculate block duration with the difference with the next block
if duration is not encoded, even if track default_duration is set.
- Use track default_duration as a duration estimate for the last
block.
- This also removes opus duration computation from encoded data.
Issues #67, #68
Change-Id: Icaa2769dcb2a89269ae014f44ad6a9262770aed2
KongQun Yang