Field order in HC and other MPEG encoders?

[zambelli]

I'm somewhat confused about the way field order is specified for interlaced video in most MPEG-2 encoders. Let's take HC for an example.

When you specify BFF or TFF in HC, are you setting the field order of the input or the output? DVD spec requires interlaced video to be TFF, but most MPEG-2 decoders have no problem with BFF video, so I can't assume that HC (or any other encoder for that matter) always outputs TFF. If the field order of the input is different than of the output, does HC perform a field dominance reversal internally?

The specific scenario, of course, would be encoding DV (BFF) to DVD (TFF).

[Audionut]

As far as i'm aware, HC always outputs progressive, unless you specify interlaced tff, bff.

And I believe that specifing tff, makes HC encode your video as tff interlaced.
ie: your output would be tff interlaced mpeg2.

[Mug Funky]

DVD spec doesn't require TFF. it just "prefers" it...

the TFF/BFF settings in HC et al tell it what the input field order is, and it then flips a bit that tells the decoder the stream is TFF or BFF.

the only difference between the 2 is 1 pixel or 1 field shift, and a DVD player is quite capable of doing that (either by moving the picture up 1, or shifting the fields along by 1).

if the DVD spec prohibited field-order setting, it'd be quite stupid. there'd be so many broken DVDs on the market.

the reason most commercial DVDs are top field first is because the masters are top-field first. the odd one out is miniDV which IMHO has confused the whole industry and buggered up NLEs (and their operators) worldwide - there'd be no confusion about field-order if everything stuck to TFF.

[zambelli]

Thanks for the info, Mug. So it sounds like in the case of DV the best thing to do is either:
1) Select BFF in the MPEG encoder and let the video be encoded BFF.
2) Reverse field dominance via Avisynth and then select TFF in the encoder, producing a more common TFF video.