Difference between field order A & B?

[ThaRealest]

I'm using TMPG and when I encode a project file, I can select either field order A or B...what is the difference between these two?

[wmansir]

With interlaced material the screen is devided up into even and odd lines. Instead of the whole picture updated at 30fps you have 1/2 of the picture updated at 60fps. So the even lines get updated, an then the odd lines. or visa versa. The field order setting tells the encoder which set of lines (called a field) to update first.

So how do you know what to set it at? First, f your source is not interlaced it doesn't matter. For interlaced sources, pick one field order, then double click on deinterlace in the box below. This should open a new window. From the drop down box pick any deinterlace menthod, then click and hold the right scroll arrow to play the video. If you picked the correct field order the video should play normally. If you picked the wrong field order the video will be very jumpy.

see here http://www.lukesvideo.com/interlacing.html for more details.