[MPlayer-dev-eng] NUT (informal) proposal, based on discussions

[Oded Shimon]

On Wed, Jan 18, 2006 at 01:29:36PM +0100, Michael Niedermayer wrote:
> Hi
> 
> On Wed, Jan 18, 2006 at 01:36:07PM +0200, Oded Shimon wrote:
> > On Wed, Jan 18, 2006 at 03:54:34AM +0100, Michael Niedermayer wrote:
> > > On Tue, Jan 17, 2006 at 09:20:02PM -0500, Rich Felker wrote:
> > > > yes, there are problems we've been discussing on irc too. some of the
> > > > problems have a fix by changing the definition of the back_ptr
> > > > appropriately, but i don't know if they all do. i'm still
> > > > investigating. will let you know when there's an update, unless you
> > > > come up with a brilliant idea first. :)
> > > 
> > > some rule like:
> > > there must be no interval of max_distance in which any stream has a keyframe
> > > but no back ptr anywhere including outside this intervall pointing to any
> > > keyframe of that stream in the interval
> > > 
> > > in our case above both K2 and K15 would need some syncpoints pointing to
> > > them to fullfill this ...
> > 
> > I'm not sure I understand this rule, but I think it comes at relatively 
> > high implementation cost in muxer...
> 
> hmm, lets see
> 1. keep track of the last keyframe of every stream (easy)
> 2. keep track of the keyframe which was the target of the last back_ptr 
>    of every stream (easy)
> 3. if last_keyframe != last_target && current_keyframe - last_target > max_dist
>         write syncpoint; 
>         last_target= last_keyframe= current_keyframe;

I'm still not 100% sure I understand, but if I'm not mistaken, this still 
fails - when writing this syncpoint, it might still point to 'last_target' 
instead of 'last_keyframe' because of dts/pts stuff...

last_target = pts 10
last_keyframe = pts 15
current_keyframe = pts 20

current dts = 13

writing a syncpoint will still point to last_target. Or did I completely 
miss something. (Also don't forget, for your back_ptr method we need to 
buffer several keyframes, not just the last one.)

- ods15