Re: [PATCH v2 04/10] media: imx: interweave only for sequential input/interlaced output fields

[khalasa@piap.pl (Krzysztof Hałasa)]

Steve Longerbeam <steve_longerbeam@mentor.com> writes:

> One final note, it is incorrect to assign 'seq-tb' to a PAL signal according
> to this new understanding. Because according to various sites (for example
> [1]), both standard definition NTSC and PAL are bottom field dominant,
> so 'seq-tb' is not correct for PAL.

Actually this isn't the case:

- real PAL (= analog) is (was) interlaced, so you could choose any
  "dominant field" and it would work fine (stuff originating as film
  movies being an exception).

- the general idea at these times was that NTSC-style digital video was
  bottom-first while PAL-style was top-first.

- for example, most (practically all?) commercial TV-style interlaced
  PAL DVDs were top-first (movies were usually progressive).

- standard TV (DVB 576i) uses (used) top-first as well.

- this seems to be confirmed by e.g. ITU-R REC-BR.469-7-2002 (annex 1).
  Hovewer, this suggests that field 1 is the top one and 2 is bottom
  (and not first and second in terms of time).

- if field 1 = top and 2 = bottom indeed, then we're back at BT.656 and
  my original idea that the SAV/EAV codes show straigh the so called
  odd/even lines and not some magic, standard-dependent lines of first
  and second fields. This needs to be verified.
  I think the ADV7180 forces the SAV/EAV codes (one can't set them
  depending od PAL/NTSC etc), so we could assume it does it right.

- a notable exception to PAL = top first rule was DV and similar stuff
  (the casette camcorder things, including Digital8, miniDV, and
  probably derivatives). DV (including PAL) used bottom-first
  universally.

I think we should stick to default PAL=TB, NTSC=BT rule, though the user
should be able to override it (if working with e.g. PAL DV camcorder
connected with an analog cable - not very probable, I guess).
-- 
Krzysztof Halasa

Industrial Research Institute for Automation and Measurements PIAP
Al. Jerozolimskie 202, 02-486 Warsaw, Poland