Field Order / Frame based.

[Trav]

Hello again folks.
I don't post in here for almost 3 months, then I put up 2 within two hours.

Ok, I Use my Marvel G200 just for editing home videos and putting em out onto VHS tape for friends and Family.
I've always been pleased with the results I've had, so never really delved into the depths of MSpro.

I've always just kept to using Frame based, but from what I've read, I'd be better off using field order A/B if i'm putting it out to tape.
Problem is, I haven't a clue about it.
What's the difference?
What does My Marvel Capture in?
Can it be changed?

Could someone enlighten me.

Thanks.

Trav

[Aryko]

Hi Trav,

The Marvel uses Field B; if you switch out of Frame-based, make sure you choose B instead of A.

The difference is that Field-based video will look much better on a regular television set, while frame-based will look much better on a computer monitor.

There are a bunch of places in MSP where you can set your preference for field-based or frame-based video; if you're just outputting to tape, I'd suggest you switch them all to field order b, especially in the create video dialogue box.

You might be getting some field "jagging" problems with scenes of lots of motion, when you create frame-based videos from field-based sources.

- Aryko

[Trav]

Hi Aryko,

Thanks for the Info.
I've got an ongoing project in MSpro at the moment, which has been set as frame based.
Can I just change it to field order B without affecting what I've already done, or should I just leave this one be!

Trav

[Aryko]

Switching from frame-based to field order b shouldn't cause a problem, just make sure to select the properties of each of your source clips and make sure they're set to field order b in there as well (you'll also have the option to de-interlace there - good if your video has lots of motion).

- Aryko

[Grigory]

Hi,

Field order specifies the sequence of rendering effects that are time-dependent:
1. Frame based, or No fields make an editor to use each full frame as single image. This result in 25/30 fps changes of picture when you apply NEW effect. For example, moving text will have 25/30 phases of motion per second. Such motion is not very smooth
2. Field based rendering. A frame is separated in two field images, and the time-dependent effect is applied to them in 1/50 or 1/60 sec steps. So, moving text will have 50/60 phases of motion per second, which gives smooth motion.

However, the editor MUST know which of two fields represent an image was shot earlier than another field. This field must also be displayed earlier, and the effect on it must have earlier phase. These earlier/later words are named field order.
If you choose incorrect order for a moving text, the phases of its motion, being originally as 1,2,3,4 will be shown on screen in 2,1,4,3 order and produce very bad flicker.

The editor does not change the order of fields in original frames. It also cannot alter the field order if you set No fields or frame-based processing. Anyway, the codec takes antire frame and make field extraction in an order that is "soldered" in the codec. So, if you apply simple static filter, you will see no difference between the frame based and field based rendering. For a static filter, you even can use incorrect field order succesfully.
However, if you force the editor to recompress everything with reverse field order option, and set processing to Field order A, you will get a movie with incorrect arrangement of fields inside a frame, which result in flickering upon normal playback on TV.

Conclusion:
1.Always make rendering with field order B.
2.If you already have movies, rndered with no fields, they are always good for field order B rendering, if they are played correctly on TV screen

Note, you can see the field order problems only on TV, because PC monitor is always used to display full frames. You just cannot see what field should be displayed first, because both of them are displayed on PC monitor alsways simultaneously

Grigory