[MEncoder-users] Interlaced DV: some questions

[Levente Novák]

Now that MEncoder is going to be raw DV-safe, I would like to ask some
experts in the matter: how to encode an interlaced content to get a DV
file correctly interlaced?

Some questions:

1. Are '-ovc lavc -lavcopts vcodec=dvvideo' encodes interlaced by
   default, or should I add 'ilme:ildct' also to lavcopts?

2. Interlaced DV is bottom-first, how to best specify it (BTW is it on
   by defalut or not?): by adding 'top=0' to lavcopts or 
   with '-vf phase=t' if the grabbing card gets it top-first? Do these
   parameters really make the video become bottom-first if it was
   captured top-first?

3. Is there a possibility to get bottom-first already at the grabbing
   phase (e.g. with appropriate bttv module parameters before launching
   MEncoder or within MEncoder by passing some switches to '-tv')?

Last time I experimented a little with Corey's DV patch applied (without
it, no DV grab using lavf was ever possible). It seems that my bt878
card is always capturing top-first, thus field order must be inverted to
get a smooth motion on playback. But irrespectively of whether '-vf
phase=t' or '-lavcopts vcodec=dvvideo:top=0' are specified, the
resulting video is more or less jerky when viewed back with 'mplayer -vo
gl -vf tfields=3'. I know that MPlayer is not supposed to honor
'tfields' but it does so, at least when '-vo gl' is used. Or should I
use something else to check whether the interlacing is done properly?

Levente