[Matroska-devel] requesting "AvgTimePerFrame" or "FieldRate" header field

madshi madshi at gmail.com
Sat Dec 15 15:21:15 CET 2012

Ok, let's make it simple. What I'm suggesting is to simply use the h264
field rate (or "frame rate = field rate / 2") for the new MKV header field.
What is important to note here, though, is that for a stream which is
encoded with telecine flags (repeat_first_field = 1), there might only be
24 encoded frames (field pairs) in the stream, but the h264 field rate will
still say 30000/1001. And this is also what the new MKV header field should
say in this case. Basically make the new MKV header field match exactly how
the h264 field rate works.

Such a solution should be easy enough to implement, no? And that's really
all that is needed for splitters and renderers to work correctly.

Of course if MKV storage works better/easier with "100000... / fieldRate",
then that's just fine for me, too. But the spec should clearly say that the
field should be based on the h264 field rate concept, to avoid any
confusion about how to mux/interpret the new field.

Best regards, Mathias.

2012/12/15 Moritz Bunkus <moritz at bunkus.org>

> Hey,
> > Maybe when you're talking about "deinterlacing", you mean weaving
> separate
> > interlaced fields together?
> Looks like I simply don't have enough knowledge in order to discuss
> this topic properly. And that leads me to doubt that I'll be able to
> implement properly...
> > Something is wrong here. If mkvmerge really sets DefaultDuration to
> > "1000000000 * num_units_in_tick / time_scale" then DefaultDuration would
> be
> > 20ms for both 50i and 25p content.
> You're right, I was wrong in what I wrote earlier. Even for 25p
> content 50/1 is used, and mkvmerge will writes 40ms as is correct for
> DefaultDuration in Matroska for 25p.
> Kind regards,
> mosu
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