[MPlayer-dev-eng] NUT cleanup

[Oded Shimon]

On Mon, Sep 05, 2005 at 09:39:12PM -0400, Rich Felker wrote:
> On Mon, Sep 05, 2005 at 03:28:25PM +0200, Michael Niedermayer wrote:
> > Hi
> > 
> > On Mon, Sep 05, 2005 at 12:47:49AM -0400, Rich Felker wrote:
> > > An additional topic: after talking on #mplayerdev today, several of us
> > > realized that the current interleaving requirement is rather stupid.
> > > Right now it says that pts must be monotone for packets with pts==dts.
> > > A much cleaner requirement would be that dts be monotone for all
> > > packets (across all streams). This is also a slightly stricter
> > > condition in the presence of high decode_delay, meaning that it makes
> > > error detection from bad pts slightly more robust.
> > 
> > hmm, i thought that monotone dts where what the spec required, its what
> > it should be and how its implemented in lavf, so id say thats a "typo"
> > in the spec, feel free to fix it
> 
> Actually after talking with uau on #mplayerdev, I'm concerned that
> muxing with monotone dts and our current definition of dts may be
> nonsense when applied in some cases with dts!=pts... :(
> 
> Consider the example where we have (I know, very stupid, but he
> insists...) a subtitle codec with I/P/B frames, and the following
> timestamps:
> 
> I0 P2 B1 [period with no subs] I100 P102 B101 P104 B103 ...
> 
> Now, the dts sequence for these frames becomes:
> 
> I0 P2 B1 [period with no subs] I100 P102 B101 P104 B103 ...
> -1  0  1                          2  100  101  102  103
> 
> i.e. the subtitle that's supposed to appear at pts of 100 gets muxed
> at dts of 2, and won't be seen when it's actually time to show it.
> Also it's not useful whatsoever to have the packet available at time
> 2, as far as I can tell.
> 
> Granted this case is pathological and stupid, but do we need to treat
> it in some way?

I think the requirement should stay the same, but the dts calculation 
should be changed in some way.
It sounds to me like the dts of I100 is '99'. If you can fix the dts
calculation to do that, I believe all will be well in the world... I have 
no idea if this is possible though.

- ods15