Another interlacing question...

[cradix]

This seems very backwards to a newbie like me:

I capture some video from my PVR using my ATI card and VirtualDub, I then take that AVI and encode it in TMPGEnc.

If I click on "Setting" before encoding and change the "Encode mode" to Non-interlace it looks great on my television, but not on my computer using PowerDVD (I see the interlaced frames). Likewise, if I set it to Interlace, it's great on my computer, but very choppy on the tele.

What gives? Shouldn't televisions handle the interlacing just fine? I think what's happening is that the AVI is already interlaced, so in TMPGEnc, it doesn't work to interlace it again (and thus choppy when played on the tele). Even still, though, shouldn't PowerDVD handle the interlaced frames on a CVD!?

It just seems like I'm missing a step somewhere. Thank you for your help as always.

-- Matt

[banjazzer]

If you choose the wrong field order, interlaced will look very bad.

[cradix]

If you choose the wrong field order, interlaced will look very bad.

You know, I've heard this before, but I guess I've never honestly tried a formal test. I just did and found out, that using Field Order B makes things choppy on the TV, but Field Order A works great!

Is the different field order a matter of different TV's or different parts of the world?

So when I've been encoding in "non-interlace" mode, is that what "progressive" is? Would a DVD player that does not support progressive scanning not play a non-interlaced MPG?

-- Matt

[banjazzer]

I'm not sure of the technical reasons, but I think it is related only to the source material and the encoding procedure, and not at all related to the way it is displayed.

Progressive means non-interlaced. So far as I know all DVD players play progressive and interlaced DVDs.

Time now for some super technical answers... 8)

[BJ_M]

field order et.al.

What are fields

NTSC video is broken into FRAMES which are delivered at 29.97 frames per second (25 for PAL). However, each frame is broken into two interlaced FIELDS. For many purposes, it is best to actually consider video to be 59.94 fields per second (50 for PAL). This is because each field is drawn sequentially, as follows:





The whole frame is composed of an active area of 720x480 (720x 576 PAL). Each field is ½ the vertical resolution of the full frame, or 720x240 (720x 288 PAL). The first field, A, is drawn on the screen from top to bottom. The BLANKING INTERVAL turn the electron beam off so it is invisible while the beam retraces to the top of the screen, then the second field, B, is drawn on the screen from top to bottom. Field A of the next frame is drawn, followed by field B, etc. Thus fields A and B represent different slices of the picture stacked together, but also have a time differential of 1/60th of a second. When you export a single frame of video as a graphic file, you will often see a comb edge to moving objects. This is the difference of position between the scan of the two interlaced fields. NOTE: You can remove this effect using the PhotoShop Filter/Video/Deinterlace filter.

What field rendering?
Many 3D video transitions and animation programs can use field renderingas opposed to the more basic frame rendering. This renders the field with a 1/60th sec time differential as is normal in video, resulting in smoother motion.

What is field order? What are reversed fields?
Different video formats and different video codecs treat either the top or bottom fields as the first field. You must know which setting is proper to use, or you will get reversed fields. DV formats ALWAYS use field 1 dominance -- LOWER FIELD FIRST!


If you mistakenly render your video the wrong way , you will see what reversed fields are. Moving object will seem to jitter. Thats because instead of playing the fields in the proper temporal order (1,2,3,4,5,6,7,8,9,10) you will be taking two steps forward and one back (2,1,4,3,6,5,8,7,10,9).

[cradix]

Extremely informative post, BJ_M! Thanks a bunch!

-- Matt

[banjazzer]

So now you know! It's because you are playing your movies in a field, instead of in the house like the rest of us. 8)

[BJ_M]

judging by the way people drive -- i would say that now days they may be watching them more in thier SUV's than at home ..