AntcuFaalb said:
russs15 said:
I remember back in 2006 when I first read the post at the link above, my head exploded!!!
All this time later, I still have no idea what it means!!!
However, as long as other people understand it, that is all that matters.
(The following uses PAL for any figures and examples.)
TV displays work in an interesting way. They use interlacing to display frames.*
Instead of showing one frame 25 times per second, they show one-half of a frame 50 times per second. Each one-half of a frame is called a field.
Now, each field is composed of every other line in a frame. So the even field contains lines: 0, 2, 4, 6, 8, ... and the odd field contains lines: 1, 3, 5, 7, 9, .... (This is the reason why separating fields results in a half-resolution image.)
There are two ways to order your fields for transmission and/or recording. You can send the even field first (a.k.a., top field first or TFF) or you can send the odd field first (a.k.a., bottom field first or BFF).
DVDs standardized on sending the even field first, so every DVD is TFF. However, TV (or just UK TV or maybe just ITV) broadcasts send the odd field first, so they're BFF.
Your DVD recorder probably assumes that its input is TFF, but your source is BFF, so your recording has the even field where the odd field should be and vice versa. This results in a combing pattern that appears to be very similar to the interlacing we all know and love.
Please let me know if you'd like me to explain further!
* The reason for using interlacing is to reduce the bandwidth needed for over-the-air transmission. Remember bunny ears?!
