Jerky video after converting from 60 to 30 fps

[Quattro Pete]

Trying to down convert a home video from 60 fps to 30 fps (actually from 59.94 to 29.97 to be exact) because some of the players can't handle 60 fps at 1920x1080. I'm using Handbrake for it. The resulting video is not smooth when panning left/right. I tried playing around with the decomb/deinterlace/detelecine, but no luck. I could have sworn I got it to work correctly in the past, but now just can't remember how. Any pointers?

 

[Kuato]

Our eyes "see" at 60fps. So with any slower speed, the frame change will be noticeable.

 

[Quattro Pete]

Originally Posted By: Kuato
Our eyes "see" at 60fps. So with any slower speed, the frame change will be noticeable.

The thing is, if I shoot the video natively at 30 fps, it is smooth and not jerky. So it's something in my 60>30 frame reduction process that causes this.

 

[Jetronic]

you need interlacing I think?

 

[BRZED]

Converting to less fps results in frames being dropped, which becomes noticeable as jerky motion in shots where the subject or the camera moves. Instead of dropping frames, your movie editor allows you to blend or to morph frames, creating smooth transistions between frames. There is also the possibility that you were using to short a shutter speed like 1/60 sec when recording. While the short shutter speed is okay when playing at 60 fps, it will look jerky in 30 fps. You can remedy that problem with ReelSmart Motion Blur in Final Cut Pro.

 

[BRZED]

Originally Posted By: Kuato
Our eyes "see" at 60fps. So with any slower speed, the frame change will be noticeable.






Our eyes can interpret a much higher frame rate than that. It's just that for all practical purposes when watching a continuous stream of still pictures the images begin blurring together to a fairly smooth motion picture at 18 fps. At 24 fps (standard motion picture) there is barely any flickering noticeable, unless the camera or the subject moves. At 48 fps (HFR, ie The Hobbit and Avatar) the image looks very steady and is not flickering to most people even if the camera or subject moves, and at 60 fps (Showscan) the image is even smoother. Too bad Trumbull's Showscan is dead. It really did look glorious even if not classically cinematic. I just read that Trumbull has developed 4k 3D at 120 fps, which may be used for the Avatar sequels.

 

[Kuato]

Originally Posted By: Quattro Pete
Originally Posted By: Kuato
Our eyes "see" at 60fps. So with any slower speed, the frame change will be noticeable.

The thing is, if I shoot the video natively at 30 fps, it is smooth and not jerky. So it's something in my 60>30 frame reduction process that causes this.



Hmmm sounds like your software in the camera automatically adjusts for it?

 

[BRZED]

In Final Cut Pro, go to Rate Conform. Uncheck Floor (which drops frames when you reduce the frame rate). Use Optical Flow (morphing) for best results. For less critcal use Frame Blending and for images without subject or camera motion Nearest Neighbor may be good enough. To reduce the jerkiness caused by too short a shutter speed, use ReelSmart Motion Blur.


http://www.revisionfx.com/products/rsmb/

 

[BRZED]

Originally Posted By: Kuato
Originally Posted By: Quattro Pete
Originally Posted By: Kuato
Our eyes "see" at 60fps. So with any slower speed, the frame change will be noticeable.

The thing is, if I shoot the video natively at 30 fps, it is smooth and not jerky. So it's something in my 60>30 frame reduction process that causes this.



Hmmm sounds like your software in the camera automatically adjusts for it?


Frame rate and shutter speed are important and can have unintended consequences if chosen on merely a whim without understanding what is involved. With an increasing frame rate the shutter speed should be ever shorter. General rule: set shutter speed to inverse twice the frame rate. For example, at 30 fps, you should have 1/60 sec shutter speed and at 60 fps you should have a 1/120 sec shutter speed. And here lies the problem: if you convert to a lower frame rate, the shutter speed at which you recorded is way too fast for the new lower frame rate. That, potentially combined by simply dropping frames instead of morphing/blending, causes the jerkiness.

 

[Quattro Pete]

It's just a camcorder. There is no way to choose shutter speed.

 

[eljefino]

Was the 59.94 shot interlaced? Is the 29.97? You can get a free program called "mediainfo" to check this all out.

Sometimes the "fields" (half frames in interlaced video) are counted, and sometimes not, so you run into nomenclature problems.

Also beware the top field first/ bottom first flags on interlaced video. Don't muck them up! Progressive scan works better on modern LED/ LCD screens, which otherwise deinterlace internally anyway.

Also consider cutting to 720p/60. This is an ATSC HD spec and most playback doohickeys can handle it.

Finally, what's the bitrate? Over 20 Mbits/sec can cause choking in various bottlenecks.

 

[Quattro Pete]

Originally Posted By: eljefino
Was the 59.94 shot interlaced? Is the 29.97?

All progressive.

Quote:
Also consider cutting to 720p/60. This is an ATSC HD spec and most playback doohickeys can handle it.

Yeah, that's what I have already done, but then I thought I'd get better picture quality if I keep it at 1080 and just cut the frame rate instead.

Quote:

Finally, what's the bitrate? Over 20 Mbits/sec can cause choking in various bottlenecks.

It's way below 20 Mbps.

 

[BRZED]

Originally Posted By: Quattro Pete
It's just a camcorder. There is no way to choose shutter speed.


Regardless of shutter speed, just improper frame rate conversionw ill cause jerkiness. How did you convert from 60 to 30 fps? Handbrake, right? Does it have options for dropping or morphing or blending frames?

 

[Quattro Pete]

Originally Posted By: BRZED
How did you convert from 60 to 30 fps?

Using Handbrake. I selected the target frame rate as 29.97 using H.264 codec. I also experimented with the various filters (detelecine, deinterlace, decomb), but it didn't fix my problem.

I don't see an option for dropping/morphing/blending frames.

Quote:
Regardless of shutter speed, just improper frame rate conversionw ill cause jerkiness.

Yes sir. That is exactly why I started this thread - to figure out what I'm doing wrong in my conversion process.

 

[BRZED]

Handbrake may interpolate well, but it probably can't compensate well or at all for motion. I think you need more capable software with control over how the frame rate conversion is handled. Probably you should ask for advice on a video editing forum.

 

[uc50ic4more]

If I am not mistaken, 59.94 and 29.97 fps are always interlaced. If the final file that was recorded is a progressive scan, it was because of a 3:2 or similar pull-down done in software processing before writing to media. The CCD's would be capturing an interlaced scan, though; and those pull-down artifacts might be contributing, by perhaps being exacerbated in the conversion, to your trouble.

 

[Quattro Pete]

Originally Posted By: uc50ic4more
If I am not mistaken, 59.94 and 29.97 fps are always interlaced.

MediaInfo is reporting the source 59.94 material as progressive.

 

[eljefino]

Way below 20 Mbits/sec is a bit low. 720 vs 1080 is kinda moot if you don't have the bitrate to support it, especially with lots of motion and detail. OTOH I "master" my youtubes at 12 MBits/sec, mostly because of my crummy upload speeds.

Can you upload the 59.94 video to a youtube account then download their processed version? They might have voodoo that you can't do.

 

[Quattro Pete]

IME, you can get pretty decent 1080 quality with as little as 5 Mbps.

Uploading the original to youtube would take me forever on my fairly slow connection. Its a 9 GB file.