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why is camcorder panning jerky when viewed on the internet?

1459 Views 13 Replies Latest reply: Nov 4, 2012 11:40 AM by Steve Fermor RSS
Steve Fermor Level 1 Level 1 (35 points)
Currently Being Moderated
Oct 27, 2012 10:40 AM

Hello everyone,

 

I'm UK based, and therefore using the PAL system, which operates at 25 fps. When I film with my HD camcorder, always at 1080, and use an iMovie 09 project set to 25 fps, and burn a DVD, panning is perfectly smooth.

I know that anything for the web or computer screens needs to be 30 fps, so when I import footage for such a project, for example to go on YouTube, I set iMovie to 30 fps and export my movie to HD.264, frame reordering off, and auto for data rate and key frames. On these movies, if anything such as a car drives across the camera view, it's fine. However, if I pan across a stationary car, the movement is jerky.

My camera is a PAL model.

 

Have I set everything up correctly and jerky panning is just how the internet is, or am I missing something?

 

And here's something really odd. If I play a PAL 25 fps DVD on my computer, it plays perfectly even though that refreshes at 30 fps. I don't understand that at all!

  • AppleMan1958 Level 7 Level 7 (27,335 points)

    Do your web stuff at 25 fps and that should cure it. The web can handle 25 fps just fine.

  • Karsten Schlüter Level 7 Level 7 (29,465 points)

    Steve Fermor wrote:

    … my HD camcorder, always at 1080, …  However, if I pan across a stationary car, the movement is jerky.

    you're using 1080i (interlaced), right?

     

    could be a 'field order problem' ...

    do you import straight from cam, using iMovie Import from cam feature?

     

    plus, try AppleMans advice first ...

    in all these conversion processes, the correct field-order can get lost.

    on the web, all material is progressive.

    if the de-interlacer 'swaps' even and un-even fields, stutter occur on horizontal movements.

  • betaneptune Level 1 Level 1 (0 points)
    On these movies, if anything such as a car drives across the camera view, it's fine. However, if I pan across a stationary car, the movement is jerky.

    When a car drives "across the camera view", you're tracking it. So it's really not moving relative to the frame, which is probably why the movement is not jerky. But it appears that any panning in your movie is jerky. Watch the background as you follow a moving car.

     

    And here's something really odd. If I play a PAL 25 fps DVD on my computer, it plays perfectly even though that refreshes at 30 fps. I don't understand that at all!

     

    The monitor does not refresh 30 fps. As far as I know, you don't have to worry about frame rates on computer monitors.

     

    AEF

  • John Cogdell Level 5 Level 5 (4,595 points)

    Hi Steve,

     

    This article may help, regarding "What is the Difference between NTSC and PAL":

     

    http://www.wisegeek.com/what-is-the-difference-between-ntsc-and-pal.htm

     

    Googling on the topic PAL v NTSC will bring up many other useful links, for example:

     

    http://en.wikipedia.org/wiki/PAL

     

    http://www.michaeldvd.com.au/articles/palvsntsc/palvsntsc.asp

     

    http://toolkit.curiousworks.com.au/knowledgebase/understanding-video-formats/pal -vs-ntsc

     

    Some of the above is a little hard to digest, but may provide a better understanding of the different frame rates and resolutions. The best idea is to stick with the same frame rate throughout your shooting, editing and exporting steps. If your camcorder records at 25 frames per second (fps) - the PAL standard - then choose this when starting a new project in iMovie.

     

    Most digital still cameras and mobile (cell) phones (such as the iPhone) record video at 30 fps (the NTSC standard). Again, if starting a project with video shot with one of these devices, choose the NTSC 30 fps option in iMovie. If burning a DVD from this project, stay with NTSC 30 fps (iDVD provides a choice when setting up the DVD authoring). Correspondingly, choose PAL 25 fps if burning a PAL project.

     

    Problems arise when frame rates are mixed in an iMovie project. I've noticed jerky playback when including 30 fps video in a project set as 25 fps. My understanding is that iMovie is deleting 5 frames every second, so the natural outcome is jerkiness in playback. For this reason I try to maintain separate projects when working with differences in frame rates. For my iPhone, which normally records at 30 fps, I now use a 3rd party app called FILMic Pro (or FILMic Pro 2), available on the App Store. This app has options for different frame rates; being in Australia, which uses PAL, I choose the 25 fps option. It works great and allows me to use my iPhone footage in my PAL 25 fps projects, with no jerkiness!

     

    For web delivery (such as YouTube, Vimeo or Facebook etc), just submit your video in whatever frame rate you've used throughout your editing process (as suggested by AppleMan1958 earlier in this thread).

     

    Hope all this helps in some way Steve. I'm no expert in this area, having just a basic knowledge of these things, so trust I haven't got anything wrong!

     

    John

    MacBook Pro (15-inch Late 2008), OS X Mountain Lion (10.8.2), Sony HDR-SR7 & DCR-TRV20E
  • Karsten Schlüter Level 7 Level 7 (29,465 points)

    Steve Fermor wrote:

    …  it does give me the option to deinterlace the source video under the size settings - should I be doing this? …

    well, best practice is not to record in interlaced

     

    the stuttering I'm noticing in your pans is - imho!! - based upon a 'not so well performed' 25>>30fps conversion. And not a wrong field-order - that would create a more 'shiver-like' panning, a much faster stutter. Yours 'hesitates' quite here and then, which - best to my knowledge - is that 25/30 conversion problem.

     

    plus, we all lie talking of 30fps - it is 29.97fps. now, do the math to create a smooth conversion to 'stretch out' 25 frames onto a 29.97-timeline ... ....

     

    I would stay in 25 on your side and look, what YT creates (I guess, they keep 25 too)

     

     

    Steve Fermor wrote:

    … To see the problem in action, take a look at one of my videos here: http://www.youtube.com/watch?v=diByNZGSa9Q

    woooonderful cars - you make me jealous!

    what a joy to see and drive (?) such pieces of art!

  • Cosme422 Level 1 Level 1 (0 points)

    You can record interlaced at 25fps all day with field renders in the basement it doesn't matter. Your render out to YouTube will re-encode your video to what you need for youtube (which yes it's progressive, no interlace fields)  I can see from your youbute video that the problem is in your render. Not sure what you are doing to render this video but the bit rate seems high in my first guess.  For YouTube I render with H264 and preferably AAC audio. If you render at 30fps, the program will duplicate frames to make up the difference. That should make your panning even smoother.  That's how I would render at 30fps (no fields) which is the same as progresive. And then after uploaded, youtube re-encodes it. I give them H264 it works great.

  • John Cogdell Level 5 Level 5 (4,595 points)

    Thanks Steve - that all makes sense. I usually try to avoid panning, unless I'm shooting a wedding video, where it's mostly unavoidable. That also applies to zooming, although with weddings it's generally necessary in order to change the framing from time to time so you can move from close-up to a wider angle without losing continuity (or vice versa). This particularly applies to the reception where you may be focussing on a close-up of a speaker and need to zoom out and pan across to the wedding party to get their reaction to the speaker's comments. At times like these, it would be great to have a multi-cam setup!

     

    A visually pleasing approach with video is to frame your shots so that you intersperse between wide angle, medium shots and close-ups. Not always easy to apply though! For example, at a kid's birthday party you could start with a wide angle of a group at the party table, then show a medium shot of the birthday child with one or two guests, then finish the sequence with a close-up of the birthday boy or girl (or reverse this process so that you gradually reveal more information, much like zooming out). Quick cutting between these types of shots is generally better than continuously running the camera whilst panning and zooming. It also helps to eliminate any jerky movement in the video.

     

    Your situation is a bit different, as you need to follow the movement of the vehicles, so panning is unavoidable of course.

     

    Good luck with your testing Steve. Look forward to hearing how things "pan" out for you!

     

    John

     

    PS Sorry about carrying on a bit about technique, just thought it might be helpful.

    MacBook Pro (15-inch Late 2008), OS X Mountain Lion (10.8.2), Sony HDR-SR7 & DCR-TRV20E
  • betaneptune Level 1 Level 1 (0 points)

    Well, I can tell you from personal experience that if you can avoid changing frame rates, avoid it! I've been working with transferred Super 8 footage originally shot at 18fps. I had no choice but to convert it. So I tried 24. Certain things break in iMovie when you change frame rates: the keywords function no longer behaves in a rational, useful manner, for example. And transitions don't preview smoothly. The help pages even warn about performance problems when changing frame rates.

     

    Only change frame rates when you have a good reason. As others have said, you don't need to change frame rates for playback on computers or websites.

     

    Additionally, I have a new frame-rate-change problem! I'll be posting that soon. But first I need to prepare some useful test samples to post.

     

    AEF

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