There has been a discussion on the list to remove the "presentation start time is derived from the first append" behavior in favor of simply defining the presentation start time to always begin at 0.[1] This simplifies many issues related to establishing the presentation timeline and the timestampOffset mechanism[2] can be used to handle content that doesn't happen to start at 0.

- Sections 6.1.3 & 6.2.3 should be removed. 
- A 2.x section should be added to indicate that the presentation start time will always be 0 and the timestamp offset mechanism should be used if the source content doesn't start at 0.

[1] http://lists.w3.org/Archives/Public/public-html-media/2012Jul/0080.html
[2] https://www.w3.org/Bugs/Public/show_bug.cgi?id=17004