[Ffmpeg-devel] [Ffmpeg-devel-old] Question about interlaced_frame and top_field_first

[Måns Rullgård]

Luca Abeni <lucabe72 at email.it> writes:

> I am also wondering how such fields are used in libavcodec /
> libavformat.  I mean: if I capture video from a bttv card, the video
> is interlaced but interlaced_frame is never set (and maybe
> top_field_first has the wrong value). What happens if I encode the
> video (for example using mpeg* with the CODEC_FLAG_INTERLACED_DCT
> and CODEC_FLAG_INTERLACED_ME flags set)?  Which kind of problems
> will I see?

Encoding an interlaced video with non-interlaced dct will give
bleeding between the fields.  This is ugly.

Encoding non-interlaced video with interlaced dct, or using the wrong
interlacedness of ME, is inefficient but doesn't introduce any
characteristic artifacts of its own.

Using the wrong field order won't show at all if the video is played
back on a computer display (non-interlaced), but looks terrible (and
may cause headaches) if viewed on an interlaced display like a TV.  It
is equivalent to swapping pairs of progressive frames.

-- 
M?ns Rullg?rd
mru at inprovide.com