[MPlayer-cvslog] CVS: main/DOCS/tech mpcf.txt,1.67,1.68

Michael Niedermayer michaelni at gmx.at
Fri Mar 4 01:44:16 CET 2005


On Friday 04 March 2005 00:23, D Richard Felker III wrote:
> On Thu, Mar 03, 2005 at 11:24:53PM +0100, Michael Niedermayer wrote:
> > > I also thought
> > > that the index entries for a section of the file would be local to
> > > that section of the file, but now it sounds to me like maybe they're
> > > distributed all over the place across all the indices, which would
> > > really be a pain since it would require leaving appropriate space and
> > > seeking back to write indices.
> >
> > yes, thats exactly why i expect to be flamed :)
> yes, i think i will have to flame, peacefully though.
> since the index is nonessential, i don't see why it's worthwhile to
> make it error resilient like this. and the disadvantages are great,

well, the index is needed to find keyframes sometimes, imagine a cd or dvd, a 
video on it which is encoded at a bitrate close to the max the drive can 
deliver and a 10sec / 300frames keyframe distance, thats a quite likely 
scenario IMHO
how do u seek in this without an index?
first problem is that the O(log n) style seeking based on syncpoints will need 
several seeks on the drive, which might be slow
but the real problem is that after u found the right spot timewise u must find 
a keyframe and based on the bitrate and 10sec interval that will need 10sec 
in worst case and 5sec average

this still applies to your proposal if a single index chunk gets damaged and u 
want to seek to its local area

another problem with it is that every chunk would store pointers to all 
previous chunks thats O(n^2) storage, so the number of index chunks would 
need to be small -> their local (unindexed if damaged) area would be large

iam really not happy with my current solution either, its just that i havnt 
found a really better one, i found a few different ones but they suck too in 
one or another way, and it could be that no solution exists to all the 
constraints & goals we are considering


"nothing is evil in the beginning. Even Sauron was not so." -- Elrond

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