[Ffmpeg-devel] interlace field order

[Ivan Kalvachev]

2006/2/21, M?ns Rullg?rd <mru at inprovide.com>:
> Dieter <freebsd at sopwith.solgatos.com> writes:
>
> > After googling a bit, I find that:
> >       Mpeg can be either top-field-first or bottom-field-first.
> >       DV is always bottom-field first.
> >
> > When converting mpeg to DV, ffmpeg sometimes outputs the wrong
> > field order.
> >
> > So the question is: how can we detirmine when the field order needs
> > to be corrected?
> >
> > In libavcodec/mpeg12.c mpeg_decode_picture_coding_extension()
> > I turned on the printf for top_field_first.  Some files have
> > top_field_first all 0, some have it all 1, and some have
> > *interesting* changes, like being 1 for awhile, then changing
> > to an alternating pattern, with 1, 2 and 3 samples:
>
> Some form of telecine, most likely.

Yes, when picture_structure is FRAME then top_filed_first and
repeat_first_field are used for telecine.