Field order

Nounours18200 · Post by **Nounours18200** » Sat Oct 28, 2006 2:12 am

We all know that we should use Upper Field First for analog video, Lower Field First for most DV camcorders.

But I regularly use an external device, an Hauppauge WinTV-250 PVR to record TV programs on my PC hard drive, and then I work on the file with UVS.

In that case, the original TV source was analog (external antenna), but the file has obviously been digitalized by the Hauppauge device.

Should I use "Upper Field First" or "Lower Field First" when working on it in UVS ?

Tks

mww1962 · Post by **mww1962** » Sat Oct 28, 2006 6:58 pm

Hi there:

I don't know what the actual technical answer is to this, but here is what I found.
I am just starting to get into this fun video stuff and bought an ADS Pyro A/V Link which outputs DV to firwire. My sources are all analog plugged into the ADS.

I captured the same one hour video using three different programs, Windows Movie Maker, Premiere Elements (bundled with the ADS....) and the TBYB VS10+.

On first thought you would think that Lower field first would be fine since a digital rendition of the source is being provided to the computer, but this does not seem to be the case as there were tons of dropped frames in the first five minutes using lower field.
Switching to Upper field during capture produced the best results, although I still ended up with 100 or so dropped frames over the length. Two spots glitchy on the old video I guess. PE captured the best copy, VS acceptable, and WMM lots of glitches.

Hope that provides some insight to get you going.

Cheers, Mike.

jchunter · Post by **jchunter** » Sat Oct 28, 2006 8:00 pm

although I still ended up with 100 or so dropped frames over the length.

You should have NO dropped frames during capture. Something is seriously wrong with your setup, your computer, or your capture properties.

As for field order, when the source video is analog, almost always, the top (even numbered) scan line was recorded first in the analog stream. The odd lines were recorded 1/60 sec later.

Users have reported that digital camcorders convert field order to lower field first but this has always confused me because it seems that it must either (1) display the later video lines earlier (jitter) or (2) interchange the even and odd lines (shimmer) but both require a significant amount of buffering in the camcorder or capture box...

Seems to me that converting field order would require more memory and real-time processing resources in the camcorder and would not produce good results.

As a practical matter, when I change the field order from upper to lower (or vice versa) in the computer, where a complete GOP could be memory resident, the results show a distinct, measureable loss of resolution and other artifacts such as jaggies, etc.

The only advice that I can offer is to preserve original field order if possible.

GuyL · Post by **GuyL** » Sat Oct 28, 2006 8:18 pm

I second John's comments. For years I captured analog video and you most definitely want to keep the source's field order throughout your entire project.

mww1962 · Post by **mww1962** » Sat Oct 28, 2006 8:37 pm

Quote:
although I still ended up with 100 or so dropped frames over the length.

"You should have NO dropped frames during capture. Something is seriously wrong with your setup, your computer, or your capture properties."

Well, nothing seriously wrong that I can think of. The same location on the video seems to drop for all programs, so I suspect source fade on the tape...it is nearly 20 years old on a VHS.

As far as the computer goes, well I am comp tech for the most part and as far as possible addressed all issues when I bought the new unit a few months ago. Short for:
Windows XP Media Centre, 1GB DDR2, 2nd hard drive - 7200 SATA2, indexing turned off, 7300GT NVidia PCIe card, firewire adapter ...nothing else major that I can think of to improve....I will really verify when I do a transfer from Laserdisc.
Any further thoughts welcome

Mike.

Nounours18200 · Post by **Nounours18200** » Sun Oct 29, 2006 7:35 am

The only advice that I can offer is to preserve original field order if possible.

I fully agree, so I suppose that an analog TV video, even if digitalized through an external device such as an Hauppauge WinTV-PVR-250, should be processed with UVS using the "Upper Field First" setting , OK ?

But regarding the digital camcorders, how to be sure that they deliver a file with "lower field first" ? is there an utility program that could check the file to confirm that the file is coded in this way ? or should we always use lower field first...

Thanks

sjj1805 · Post by **sjj1805** » Sun Oct 29, 2006 11:59 am

The Hauppauge TV cards are Analogue and are Upper field First.

Nounours18200 · Post by **Nounours18200** » Sun Oct 29, 2006 2:31 pm

Tks, this is what I thought...

GuyL · Post by **GuyL** » Sun Oct 29, 2006 2:37 pm

Nounours18200 wrote:
is there an utility program that could check the file to confirm that the file is coded in this way ? or should we always use lower field first...

Thanks

http://www.avlandesign.com/dl_GSpot.htm

Nounours18200 · Post by **Nounours18200** » Sun Oct 29, 2006 6:32 pm

thanks GuyL

jchunter · Post by **jchunter** » Sun Oct 29, 2006 7:17 pm

Guy,
I just downloaded GSpot and it doesn't immediately show the field order property. Is there some way to configure it to show?

Nounours18200 · Post by **Nounours18200** » Sun Oct 29, 2006 8:25 pm

good question...

GuyL · Post by **GuyL** » Sun Oct 29, 2006 11:35 pm

jchunter wrote:Guy,
I just downloaded GSpot and it doesn't immediately show the field order property. Is there some way to configure it to show?

No, it should display automatically. TFF = Top Field First and BFF is Bottom Field First. If you hover your mouse over the acronyms it will tell you what they are.

jchunter · Post by **jchunter** » Mon Oct 30, 2006 12:10 am

Guy,
I downloaded version 2.21 and, while my eyes aren't as good as they used to be, I can't see the words "TFF" or "BFF" or Frame on my Divx or Xvid or H264/ACV videos. Although every other property is reported correctly.

What field does your copy display field order on?

It will not report information on mpeg files at all, either standard or high def. It displays only "n.a." - not available.

Post by **Ken Berry** » Mon Oct 30, 2006 12:19 am

Thanks for the GSpot link to the upgrade version -- I have been using version 2.21 for a couple of years now, and it did not show the Field Order (though that was not why I was using it anyway -- only for checking the codecs on my computer).

I have now used version 2.60 beta 2 though I am not sure I will install it. Curiously enough, it shows all my DV Type 2 captures from my Canon mini DV camcorder as being TFF (Upper Field First), when I know they are -- as they would be from the Canon -- Lower Field First or BFF in GSpot parlance. Yet the DVD-compliant mpeg-2s I made from those same DV clips are (correctly) shown as Lower Field First. What is more, those mpeg-2s play perfectly both in my computer and on burned DVDs played in a stand-alone player on an analogue TV. So there seems to be something strange, and probably wrong, about the GSpot readings in this case. (I tested it on a number of different DV captures made at different times and stored in different folders and drives on my computer.)

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