• Adobe After Effects

  Rendering for DVD and using Fields

  Posted by Mark Whitney on March 8, 2007 at 2:34 am

  Hey folks,

  I’m using AE7 to convert some older material that is in D1 (720 X 486), Lower Field First format into mpeg2-DVD for subsequent authoring. I set the source AVI footage interpretation to LFF, Preserve Edges, etc. and create a new D1 comp from it. I then create a new DV rez (720 X 480) comp and bring the D1 sized one into that and simply center. I’m cropping the top & bottom 3 rows to clean up some time code garbage and the like at top & bottom, and this preserves field order and pixel size.

  I’m confused though whether I actually need set field rendering to match for my output module settings when choosing the MPEG2-DVD format and using the MainConcept codec as it’s panel also gives a field order tab.

  Thanks,

  Mark

  Mark Whitney replied 19 years, 2 months ago 2 Members · 4 Replies
• 4 Replies

• 

  Filip Vandueren

  March 8, 2007 at 3:53 am

  DVDs / MPEG2 streams can be both upper or lowerfield, as long as the right flag is set in the metadata.

  So if you want fields, you should choose either setting in the outputmodule, and stick to it when encoding.
  I Don’t know MainConcept, but it should be able to choose the fieldorder.

  In AfterEffects, I would choose upperfield first,
  because when trimming 3 scanlines from a lowerfield clip,
  the 4th line (even) becomes an odd line (line nr 1).

  If you would use LowerField (even), the First line would have to contain motion from the second field in time,
  so it would actually have to obtain it’s information from the odd lines by interpolation and vice versa

  Hope that makes sense 8-/ It’s hard to explain.

  Anyway, in theory you would get less interpolation…

  You could also NOT interpret as interlaced, NOT render as interlaced, and you would still wind up with a file that looks UPPERfield.
  Bar compression artefacts, this might be the cleanest solution (and fastest render).
  But it’s a bit dangerous: a nudge of 1pixel down would reverse the field order.
• 

  Mark Whitney

  March 8, 2007 at 8:20 pm

  I think that’s part of the confusion: Is a FIELD also 1 Pixel in height, or is it 1/2 pixel?

  Mark
• 

  Filip Vandueren

  March 8, 2007 at 9:14 pm

  A field is half of the lines in your frame,
  the odd lines and the even lines form respectively the upper and the lower field,

  every line is indeed 1 pixel high,
  and a field theoretically has the height of your comp/2
• 

  Mark Whitney

  March 9, 2007 at 4:01 am

  Ah. OK. So even though fields are referred to as “lines”, as far as AE is concerned they end up 1 pixel in height.

  Thanks. That clears the confusion.

  M.

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