Motion "Strobing"

[Roger Shealy]

Is there a way to help smooth out HD motion in Vegas Pro? Often, even with slow pans and tilts my video has "stuttering" or strobing effects in the detail that are very distracting. Take time 0:09 - 0:12 in the video below (visible in Vimeo and the original as well):

180 Degree Farm on Vimeo

I'm using Vegas 9 in a 1080-60i project (no 30P and I've tried HDV-30P), shooting with a 7D in 1080P, rendering to 720-30P.mp4. The clip in question is slowed down 50%, so its worse than usual, but motion often not silky. I've had the same issue in earlier versions of Vegas shooting XHA1 and other cams and even in 100% speed they often look choppy compared to other footage I commonly see. How can I make things "flow"?

[Gerald Webb]

I would like to hear some input on this as well.
I've shot a bit of 720p 50fps lately hoping to get rid of it, to no avail, its still there.
Is it Vegas? the codec?
there's nothing worse than a nice slow pan that seems to skip.

[Jeff Harper]

The phenomenon is normal. When panning against a busy background like the flowers, greenery the problem will be worse. 30p/24p especially this will happen. If you are not following a moving subject it is the most noticeable.

Shooting in 60fps can help. This is common even in expensive 24fps "hollywood" film cameras. You simply need to shoot accordingly, unfortunately.

Try panning the blue sky with clouds, and you'll see the problem is likely not there. It just depends on what you're shooting and your frame rate.

[Roger Shealy]

Jeff,

I'm aware of strobing of 24P and 30P to a lesser extent, but these are painfully slow movements. If I catch the gist of your thoughts, high detail movement exacerbates the strobing of slower pan rates (make sense as the flowers/branches have to move from frame to frame)?

Have you had any success using motion blur or something like that. I've heard of others in FCP using tools to smooth slow motion, seems this is somewhat similar.

[Ben Lynn]

The solution is to right clip on the clip in the timeline and go to the properties menu. Check the box labeled "Disable resample." The default is set to Smart Resample and that causes the problem.

Don't ask me for the technical reason why that happens, I only know it has to do with frame interlacing and that disabling the resample will pull a clean 30p off the timeline and eliminate the strobing you see.

Unfortunately, you have to uncheck that for every single clip when your going to the web. Or maybe someone knows how to change the default setting to disable it. Tell me if you do because it would save me some time for sure.

[Jeff Harper]

Roger, it's not just how slow the pan is, it is the subject matter. A very busy or detailed background will do it. Even hollywood cinematographers have to set up their shots to avoid this exact same thing. I personnally just accept it and it doesn't bother me, but that is just me.

If you move in closer to the subject (enlarge subject) you will eliminate some of the issue, but bottom line, I believe is you must shoot according to the limitations of the gear. I would never expect the pan of flowers like you did to NOT be jittery. I would expect it. I would move in closer, or shoot a slow zoom in or out of that subject, but not a pan. That is just how I see it.

[Roger Shealy]

Ben,

Thanks for the tip. I'll give it a try and see what happens.

[Jeff Harper]

Ben, if you say that disabling resampling helps, I believe you, but I wouldn't think it would affect this particularl issue by itself. It might help a bit, as it does with slo-mo, but not enough to solve the issue.

I use that setting for slow motion footage, and it helps a tad. This subject of how to shoot in Hi-Def and in 24p and 30p has been beaten to death in many forums. Trying to fix this phenomenon, I believe is fairly hopeless, as the issue lies with the footage.

There is an article somehwhere I can't find right now that covers how to pan properly with this gear. If I run across it I will put up a link for you Roger.

There are extremely expensiive cameras that suffer form this issue. So in a technical sense there is nothing wrong, you are simply shooting beyond the limitations of the camera.

Hi-Def demands more from the shooter and is not as point and shoot as SD was. As beginnersin with HD this is the most important lesson we can take from this situation. As one professional said when HD was introduced, "HD brings back the craft to shooting".

There is a method of fixing slow motiion footage by putting up a second line of the footage on top and then shifting it a frame or so, and lowering the transparency, etc that might help with this issue. Do a search for fixing slow motion footage and you might get some help, but again I don't know if it will help with this panning issue.

[Ben Lynn]

This thread is starting to combine and address a lot of issues that aren't necessarily related to the original post but maybe that's a good thing.

The original problem was purely a technical issue dealing with frame interlacing and resampling, not a film technique issue. Roger is shooting at 60i and he needs it to look good on the web. Right now he's getting ghosting in the image. That's why he needs to disable the resample rates so that the editor pulls a clean thirty frames off the footage instead of blending the sixty frames into thirty (which creates the ghosting effect). Pause the video and you'll see a dual image during the faster moving portions like the chicken. I paused the video at :25 sec and the brown chicken has two eyes. Right after that the white chicken turns it's head and if you pause the video as it turns you'll see two heads. That's the ghosting effect and it's purely a technical adjustment within the editor.

If you shoot 60i or 60p and then slo-mo it to 50%, you can disable the resample and get footage that's totally clean and full frame rate without the strobing. And maybe this is where some confusion is happening. Roger probably should have titled the thread "ghosting" rather than "strobing", but it's all good.

Strobing typically occurs when you have only 30, or 24, frames and then try to slow it down. There aren't enough frames so it results in a strobing effect (too much motion within the frame between frames). But that's different than the original problem and not an issue here because Roger's shooting at 60i. Again, he can slo-mo it to 50% without any strobing effects. Strobing will appear if he drops the rate below 50% and the frames have gaps to fill. And even if you slo-mo footage you still need to disable the resample if you want to avoid blended frames. Other strobing situations result when there's too much motion within the frame and that's the area that may or may not be fixable. If you fix the ghosting with the chickens you'll find that it results in a strobing motion because they move through the frame so fast. That can't be corrected, they simply moved too quickly.

Rogers content and technique were all solid and shooting with a "film" technique wouldn't have eliminated the technical issues with the ghosting. A certain amount of strobing, or blur depending on your settings, will be inherent with any footage running at 30p on the web in certain situations. That's where good camera techniques may or may not help to minimize the effects. Certain situations can't be corrected, like too much motion within the frame. But before you address any camera techniques, you have to make sure the technical problems are eliminated first. Otherwise you could waste all your time trying to eliminate the ghosting by making super slow pans, while the whole time all you had to do was click a setting on the clip. Now if you disable the resample and still see strobing, then you need to address the technique aspect of the production. But in this particular video the technique was all solid and it was a technical issue.

You can make fast pans and it can look good. But that depends on the content and the focus within the frame. Each situation is different and one technique doesn't apply to all situations.

Also, you should set up your timeline as a 30p timeline so that you can see what it will look like on the web as you edit.

[Roger Shealy]

Ben,

In Vegas 9 I don't see a 30P option for HD. I see it for HDV, but not HD, so I use HD 60i.

How do you set the timeline to 30P for HD?

[Jeff Harper]

Originally Posted by Ben Lynn

The original problem was purely a technical issue dealing with frame interlacing and resampling, not a film technique issue. Roger is shooting at 60i and he needs it to look good on the web.

Ben, when shooting in HD, the strobing issue always occurs when panning against the type of background he was filming. This absolutely is a filming issue.

Why is the issue not present in the other shots? Because he wasn't panning a detailed background. As I said this has been discussed in many forums, with many people not understanding the issues with shooting HD, even at 60i. It was one of the first things I learned when shooting with the FX1000 two years ago, or whenever it was released.

I did a search last night and this issue comes up often: people wanting to know why their pans are jittery on their new HD cameras. It is the nature of the beast.

We can agree to disagree, I suppose, but if I didn't want strobing of my pans I would simply plan my shots accordingly. The shot of the flowers he executed, ideally should have been a still shot. And if he knows it is going on the web, we know that movement is always much more iffy when playing back in flash anyway.

With a busy background (background with lots of detail) one should at least get a still shot for backup in case the pan shot doesn't work.

I admit I cannot offer a solution to his immediate issue with his current clip, but on the other hand if he shoots appropriately in the future the problem will vanish.

Just my 2 cents.

[Craig Longman]

I was wondering how the disabling of resampling worked here. Looking at a paused slo-mo, it seems like it would be a big help.

Jeff, if you go to the 12s part and pause it, you can clearly see a double image every other frame or so. As you point out, things might well look 'jittery', as in something jumping from point to point, particularly at slower frame rates. And, as you point out, it gets way, way worse when dealing with highly detailed backgrounds.

But I cannot see how that accounts for the double image?

You won't get that shot looking perfect, but I think that strobing effect will be significantly reduced. Now, it's almost as if it goes in and out of focus, and all because of that double image you can see.

[Jeff Harper]

Craig, I don't know the cause of the issue (other than the cameras doing it some pans) , and I can't explain it either.

I'm sure there might be a fix, or sorts, as you say, to lessen the effects. I don't know the technical reason for the problem...and truth be told I don't pay tons of attention to technicalities as I should. I personally just do what I need to to get my subject matter recorded in the best way and get paid.

Even if there is a fix of sorts, I would think it would be easier to shoot differently. When following a subject with a pan the problem is not noticeable because the focus of the viewer is on the subject, not the background and that is what I'm often doing, shooting moving subjects.

Learning a bit about shooting HD has made me a somewhat better shooter than I was, so I believe it is all good in this case. I don't actually shoot in HD now, but tried it for while when I first got an HD camera. The habits I developed shooting events in HD has made my footage much more watchable. Since I'm self-taught, I need all the education I can in proper filming tecnique.

[Jeff Harper]

I have read what the cause of the issue is, but I can't remember what I read. It might be a CMOS related thing...but I'm sure someone will come along here and give us the actual answer.

[Roger Shealy]

I've pulled out the segment in question and run it through various variables; 1080P vs 720P; 15Mbps vs 6 Mbps; 100% vs 50% speed; resampling on and off; and you of course can see impacts of these on Vimeo and download and compare uncompressed.

Strobing Test, 1080P-15Mbps.mp4 on Vimeo

Strobing Test, 1080P-6Mbps.mp4 on Vimeo

Strobing Test; 720P-6Mbps.mp4 on Vimeo