[Matroska-devel] Re: MPEG2 in MKV!

spyder spyder at matroska.org
Thu Oct 30 18:29:29 CET 2003


>The third and fourth
> images are combined so that the image sequence looks like this:
>
> [Aa][Bb][Cc][CD][Dd]

Ummm, RFF repeats the first field last ie, in 121 order. not 112. :P

Your output sequence would be:
[Aa] [Bb] [Cc] [CD] [dD]

Check a dvd video decoded without force-film, the 4th and 5th frames are 
combed.

>
>
> There are two ways to handle the pulldown. You can store it like its stored
> in MPEG-2, or you can 'fix' it an remove the pulldown.

Bad idea to remove the pulldown.  MPEG decoders expect constant framerate and 
you can't change the framerate to 24fps becasue you would need to drop some 
frames which would break the encoding scheme of mpeg2.  (ie, removing data 
referenced by other frames)

>
> 1. Store the four frames with timecodes like you are going to store 5
> frames. The fourth frame will have a duration that is twice the duration of
> the other frames.  This should leave space for the decoder to generate the
> extra frame.

Yes.  i agree with this.

> 2.  Forbid pulldown.  When transferring the frames into MKV, you set the
> RFF flag to 0, change the framerate, and space the frames out for what
> actually exists.

NO NO NO NO NO NO

> John pointed out that you shouldn't force people to use progressive, but I
> say you can encourage them.  So, I vote that we have both methods as an
> option in muxing tools.  The default should be option 2, but you could set
> option 1.

See above :P


John



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