On Wed, Feb 20, 2008 at 05:23:14AM +0100, Michael Niedermayer wrote:
Hi
When we designed the pts->dts reorder algorithm we considered arbitrary frame reorderings, but there was something we missed, that are mixes of frame and field pictures, like:
i1 p2 P3 p4 P5 p7 P8 (lower case is a field, upper is a frame) PTS 2 3 4 6 7 9 10 DTS 0 1 2 4 5 7 8
As you can see no reordering of PTS can result in the DTS values.
I'm confused by this example. As there are no B frames, dts==pts is just fine.
The reason why this fails is (if my brain still works at 5:30am) that frame pictures contain 2 fields and thus would have to be counted like 2 besides that they would really need 2 pts.
Presumably interlaced video is always fixed-fieldrate, and the device presenting it knows the time interval between fields. This is why I never saw storing an explicit timestamp for the second field as important..
I suspect some solution based on dummy 0byte packets with the missing pts after each frame might solve this, but i must think more about this ...
Sounds ugly. I'd like to see a lot more motivation of a need before anything like this is considered.. Rich