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contrary explainations for video field!

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Shawn Hyper
contrary explainations for video field!
on Aug 14, 2012 at 3:57:28 am

Recently, we have encounted a rendering problem of jagged edge. And I have searched the net for relevent infos. Guess what I have found?

http://support.apple.com/kb/TA26010?viewlocale=en_US

The link above is Apple's official explaination for field. It's obvious that figure 3 is not correct, it should be flipped over right-to-left.
And the most important thing is that Apple says in FCP Field 2 is the upper field!!!

Then check this link below:
http://www.dvmp.co.uk/digital-video.htm

It's obvious that Field 1 in fact is the upper field!!!

Terrible!!!


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Shane Ross
Re: contrary explainations for video field!
on Aug 14, 2012 at 4:29:14 am

Depends on the resolution. SD and HD are different when it comes to field order. In SD, Upper is odd. in HD, lower is odd. WHY? Who knows why. Stupid engineers. They like to call 30fps at 1080i...1080i60, but 720p60 is 60 frames per second.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Rafael Amador
Re: contrary explainations for video field!
on Aug 14, 2012 at 6:03:41 am

[Shawn Hyper] "The link above is Apple's official explaination for field. It's obvious that figure 3 is not correct, it should be flipped over right-to-left."
You are right.

The fact is that Apple is messing things by bringing that graphic here.
That's the representation of a SD ANALOG signal where the UPPER (always ODD lines) field end up with half line and the LOWER (always EVEN lines) field start with half line.

In NTSC analog each field has 262,5 lines (525/2). The line 263 (half) is the last of the first field and the first (half line) of the second field.
In PAL analog each field has 312,5 lines (625/2).

In an analog signal DOESN"T EXIST FIELD ORDER or FIELD DOMINANCE. Frame always start with the UPPER (ODD) field because the natural way to scan a picture is by starting with a full horizontal line, no with half. This the way cameras scan and monitors display. In any Analog segmented format (1"B, Betacam, VHS), the first field from any frame is the Upper.

[Shane Ross] "Depends on the resolution. SD and HD are different when it comes to field order. In SD, Upper is odd. in HD, lower is odd. WHY? "
No really, Shane.
Upper and Odd (or Lower and Even) means the same in SD and HD.
rafael

http://www.nagavideo.com


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Shane Ross
Re: contrary explainations for video field!
on Aug 14, 2012 at 6:11:56 am

[Rafael Amador] "No really, Shane.
Upper and Odd (or Lower and Even) means the same in SD and HD."


I heard different. But I haven't had to deal with interlaced for...well, a VERY long time. So i could be wrong.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Shawn Hyper
Re: contrary explainations for video field!
on Aug 15, 2012 at 4:09:05 am

Thanks for all the replys.

It seems obvious that Apple, at least the author who wrote those words, makes a mistake as for the explaination.


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Andrew Rendell
Re: contrary explainations for video field!
on Aug 14, 2012 at 6:44:08 am

TBH there is so much duff gen in the internet that I religiously stick to the internationally agreed official terms, i.e., always refer to field 1 and field 2, NEVER to upper/lower, top/bottom or odd/even, because those unofficial terms are so often misunderstood.

Even odd/even lines is misleading because the official way of numbering lines, and therefore what you will find on proper test gear, is sequential by scanning order (so the lines number down field 1 and then down field 2), not by position on the screen.

In the UK, where I am, HD broadcast is 1080i50 so these things do come up from time to time.


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Bouke Vahl
Re: contrary explainations for video field!
on Aug 14, 2012 at 9:53:27 am

in SD, all codecs are UPPER, except DV, that is lower.
Except Avid DV, that is upper. (good choice back then to be able to mix codecs, but a bit confusing)

Bouke

http://www.videotoolshed.com/
smart tools for video pros


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