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Old August 22nd, 2007, 10:47 AM   #1
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Strobing problem

I'm working on my 4th program shot with my 350 and am having a very strange strobing problem on import into FCP.

Look at the attached photo.

This is how the footage looks after import, and for that matter exported back to disc. When playing back on the monitor after export, the strobing is quite noticable on the big screen.

BUT, put the master disc in the machine, and it plays just fine. No strobing whatsoever. Lovely, beautiful video.

But import it into the Mac, (FAM/XDCAM Transfer) and it does not matter if it is on the timeline in FCP, or just the computer playing it in Quicktime Player, the strobing is there.

I've used other footage from this trip in another program, and it looked just fine. I never changed the camera settings in the trip.

I'm shooting 1081/60.

I had thought that perhaps it was a shutter issue, but again, the original plays just fine camera into monitor. But I have this nasty habit of wanting to edit my footage, and that is where the problem comes in. Any and all help is appreciated.
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Old August 22nd, 2007, 01:55 PM   #2
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Looks like a frame rate issue, like a conversion from 50i to 60i. As the original material is clearly OK I suspect either a codec issue or simply the wrong frame rate being set.
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Old August 25th, 2007, 12:58 AM   #3
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Les, tell us your exact path.

The still shown, to me ,looks like each image is a field.

On which display is the strobing happening? Just the computer? How are you monitoring in FCP?

Again, relaying your exact path and exactly on which displays you see this is key.
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Old August 26th, 2007, 01:02 AM   #4
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Some answers

Gentlemen,

Sorry for the delay in response. This particular program was a "non revenue" project. We shot a couple of "revenue" projects in Canada and Alaska, and the program in question above was a recount of our journey for family and friends.

The deadline was today, as there was a big showing at church.

But, of course, I need to solve the problem, as the "real" programs are next.

Shorty after I made the first post on this forum, I tried deinterlacing, and as Nate mentioned, that was the problem. Didn't have time to post my findings as I had a show to get done!

I noticed a slight increase in noise in the picture, but it still looks great to the eye, and the church audience went on and on about the content of the program, so, in there eyes, everything was fine. And I must say, sitting back at viewing distance, rather than my eyeball 3 inches from the screen, I did not notice anything either.

I'll take a look later and try to figure out what the problem was.

The footage was shot at 1080i/60. That is what the camera is set at, and it plays back the discs without any mention of having to change the settings for playback.

The sequence in FCP is also set at 1080i/60 and XDCAM 35, so I am really puzzled.

It's late, so I'll fiddle around later to see if I can figure out what happened. I solved the problem to make my deadline, but of course the "solution" should never have hade to be done in the first place.

Thanks for your suggestions.

Les
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Old August 26th, 2007, 01:24 AM   #5
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Again, though, you're not really telling the needed details.

Are you seeing the strobing when making an SD DVD of the footage? Are you seeing it when monitoring out of FCP?

If you're seeing it making regular DVDs, beware that FCP/Compressor does not make 480i M2Vs correctly from interlaced 1080 without intervention. So that's maybe one thing.

Regardless, it's clear there's a field blending or order issue, but can't say any more until you give more details.
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Old August 26th, 2007, 10:13 AM   #6
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Quote:
Originally Posted by Les Jarrett View Post
The footage was shot at 1080i/60. That is what the camera is set at, and it plays back the discs without any mention of having to change the settings for playback.

The sequence in FCP is also set at 1080i/60 and XDCAM 35, so I am really puzzled.

It's late, so I'll fiddle around later to see if I can figure out what happened. I solved the problem to make my deadline, but of course the "solution" should never have hade to be done in the first place.
The camera has no playback settings to change. It plays back whatever the material was recorded at. In fact, the camera must be set to the same mode as the recorded material to even play it back at all.

TV sets are interlaced which is what you shot. Computer screens are all progressive. If you play back interlaced material on the computer screen, you will get interlace artifacts. That's why it's necessary to have an interlaced display device attached to the computer so you can view the material properly if you are going to shoot interlaced. Or, you can do what you did and de-interlace in post to see it (with lower resolution) on a progressive display without artifacts.

Right now, US HD broadcasts are 720P or 1080i. So you need a monitor capable of displaying both modes.

-gb-
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Old August 26th, 2007, 12:08 PM   #7
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Interlace problem

Greg,

The problem is, the interlace/strobing problem was glaring on playback into a real, not computer, monitor.

Currently I don't have any way to check the footage i've edited other than to dump it back into the camera and play it back on the monitor.

That is actually where I discovered the problem.

Not an ideal situation, I agree, but small producers have to build the system in stages, sometimes.

If this was my old analog system, it would have been disovered at once.

I'm going to try to replicate the problem. I was careful to set the sequience at 1080i/60, and when I noticed the problem, that is where I first looked. It was 1080i/60.

Thanks all for your comments.

Les
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Old September 6th, 2007, 12:38 AM   #8
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Narrowing it down

Gentlemen,

OK, here's what seems to be happening.

In a nutshell, the clips are importing at 29.97. The problem is, they were shot in 59.94i.

In XDCAM transfer, the frame rate clearly says 59.94i.

I've attached several screen shots so you can see what I am looking at for yourselves, hopefully it will be helpful.

As you can see, I'm importing everything at 29.97.

What about export?

I took a clip, and just to be sure, in Compresor, I converted it to 59.94i.

Dropped it into my FCP sequence that I have pictured. Tried to export to the camera. Got, "assertion failure: valid media time scale".

The camera is set at FAM, 60I, HQ. Just to be sure there, I tried exporting back to the disc that the the original files are on. The originals are at 59.94, and I tried to export back that way.

The camera is only accepting clips at 29.97. 59.94 gets the assertion failure.

This one has really got me stumped. It's late and my brain may be dead, but I just can't figure this one out? Should not clips shot at 59.94 import at that rate? It would seem I've changed something in FCP, but I don't know what. Any thoughts?
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Strobing problem-picture-15.png   Strobing problem-picture-16.png  

Strobing problem-picture-17.png  
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Old September 6th, 2007, 02:27 AM   #9
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Les,

29.97 and 59.94i are two ways of saying the same thing. They both mean 29.97 frame rate, interlaced.

The problem lies in that when you change the editing timebase in the FCP sequence settings to 59.94, FCP is thinking 59.94 FRAMES per second. 59.94i means 59.94 FIELDS per second. Get it? You've overthought the process and made your own sequence that is wrong. This is also why you're seeing a red render bar above your footage in the timeline. Fix this, and you'll be able to play your clips without rendering.

59.94 frames per second is a valid framerate for 720p material ONLY, that's why it exists as an option in FCP.

Below is a shot of what you sequence settings need to look like: (by the way, FCP has XDCAM HD sequence presets for every mode the camera shoots. All I did was load the sequence preset to get the settings below)
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Strobing problem-fcp.jpg  
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Old September 6th, 2007, 02:34 AM   #10
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Chasing my tail!

Nate,

Thanks for your reply. Yes, I've overthought it, as the settings you show are what I used to begin with, on the church program that started the thread.

It's really puzzling. A clip looks beautiful playing from the camera, then has this interlace problem upon editing. If I de-interlace, it looks fine on my HD monitor. Of course that is not really the solution to the problem, although most of my customers won't notice. Some of them are upset that I've phased out VHS!

But I'm looking to the future, and want to get this workflow right.

The thing is, my prior XDCAM HD programs don't have this problem, I'd have noticed it right away. I can't for the life of me figure out what is going on.

Off to bed. Too many hours staring at the screen!

Thanks again,

Les
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Old September 6th, 2007, 10:31 AM   #11
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Problem Solved

At last found the cause of the problem.

Was looking in the filters, and each and every clip has a filter enabled for "shift fields" +1.

The mystery is why this is, as I did not set a filter for this. Is there a global setting that I somehow enabled?

Anyway, take away the shift fields, and the train goes by normally!

Thanks all for your thoughtful remarks.

Les
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