> On Sep 1, 2015, at 11:36 , Kevin Marks <kevinma...@gmail.com> wrote:
> > I suppose the browser could generate this data the first time it reads 
> > through the video. It would use a lot less memory. Though that sounds like 
> > a problem for the browsers to solve, not the standard.
> There is no *generation* on the browser side; these tables are part of the 
> file format.
> Well, when it imports stream-oriented media it has to construct these in 
> memory, but they can be saved out again. I know that in theory this made its 
> way into the mp4 format, but I'm not sure how much of it is real.

Two different questions:
a) do the QuickTime movie file format and the MP4 format contain these tables?  
b) if I open another format, what happens?

For case (a), the situation may be more nuanced if Movie Fragments are in use 
(you then get the tables for each fragment of the movie, though they are easily 
coalesced as they arrive).

For case (b), classic QuickTime used to ‘convert to movie’ in memory, building 
the tables.  The situation is more nuanced on more recent engines.

I think the point of the discussion is that one cannot dismiss trick modes such 
as reverse play as being unimplementable. 

David Singer
Manager, Software Standards, Apple Inc.

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