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Video switching between upper and lower fields?
I’m editing video that another company shot on digibeta. It’s a long story, but because of problems with a previous copy of the video I was editing for broadcast, I had to get another copy from the company that made them originally.
I uploaded the video for broadcast, and the broadcaster says that the video seems to alternate between upper and lower fields first, even though I’m rendering in mpeg2 for Upper Field first and I checked every video event and they’re all upper field first.
How is this possible?
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11 Replies
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[Angelo Mike] “I uploaded the video for broadcast, and the broadcaster says that the video seems to alternate between upper and lower fields first, even though I’m rendering in mpeg2 for Upper Field first and I checked every video event and they’re all upper field first.
How is this possible?”
It would be possible if Vegas guessed wrong. You should use a program like MediaInfo or GSpot to check the field order of the clips. If one of them is Lower Field First and Vegas thinks it’s Upper Field First (or visa versa) that would cause this problem. The solution would be to right-click on the event on the timeline that is wrong and change the field order to the correct one.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
I didn’t use either of those programs, but I checked the field order on each event, and they all say Upper Field first.
I’m going back and forth with revisions to the video now with the broadcaster, and they’re not mentioning the field order while we work on other stuff. That could just mean they’re waiting to tell me about that last, though.
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I assume your project is correctly set to Upper Field first? Try turning off resampling on all clips. Which encoder are you using? I think the MPEG-2 DVD settings will encode bottom first…
Lance Bachelder
Writer, Editor, Director
Irvine, California -
[Angelo Mike] “I didn’t use either of those programs, but I checked the field order on each event, and they all say Upper Field first.”
Well… they’re both free and you need to use them if you want to solve this because what Vegas is showing might be wrong and you can’t correct it unless you know for sure.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
It seems like the video passed quality control. Of course, this is subject to revision at any moment, but I’ll download one of those programs if this is still an issue. Thanks.
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Note that all these utilities (MediaInfo, GSPot) read media attributes from the file headers and if Field Order flag is wrong, they won’t help you. Some video file formats do not contain information about field order.
The best way to identify the correct field order (100%) is to use external TV monitor. There are some utilities (like AVISynth scripts or Vegasaur Field Order Analyzer) that can help you to identify the correct field order without such monitors (just using Vegas Preview Window)
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Upon reading this I am interested to know if the problem with the fields actually shows up as something you can visually see when viewing it in a television monitor or is it one of those things that just gets the thumbs down from the broadcaster as not being correct.
What actually happens in the final viewing to flag it as bad.
Roger Bansemer
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I wouldn’t know-I render it for broadcast and then upload it to an ftp site that they test for quality control. I just got word that it worked fine, and I changed nothing about the field order, I don’t really know what happened.
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[Roger Bansemer] “What actually happens in the final viewing to flag it as bad.”
If the field order is incorrect, the video would stutter any time there was movement because it would show the motion as jumping back and forth between the fields that were out of time. The cadence would be something like “one step forward, two steps back” as you see field 2 before field 1 then field 4 before field 3, etc.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
[Angelo Mike] “I just got word that it worked fine, and I changed nothing about the field order, I don’t really know what happened.”
This happens more often than you think. We have had tapes rejected that we didn’t feel there were any problems with and so we simply sent the exact same tape back and they passed. It depends on what engineer gets the tape and I it must have something to do with what mood they’re in that day. Broadcast is not an exact science. 😉
~jr
http://www.johnrofrano.com
http://www.vasst.com
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