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Question for phantom-Videomakers: jerky 4K footage

Discussion in 'Pro/Adv Discussion' started by fabbio, Jan 20, 2016.

  1. fabbio

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    Dears,
    I don't know if someone already solved this problem, but sometimes I have jerky/stuttering 4K footage from my P3P as if some frames were not recorded at all.
    Problems are right into the original file taken from the bird, so naturally also in the relative Apple ProRes 422 converted ones.

    Stuttering happens in a unpredictable way, apparently random (even if somewhere I read about a possible connection with the complexity of the image in a particular moment).

    My conditions, also in order to rule out possible variables from the equation:
    • shooting 4K, NTSC, 30fps, LOG, MOV format, no ND filters (but stuttering happens also in low light conditions)
    • usually in long landscape pans scenes
    • branded memory cards, personally checked for 160 Mb/s writing and reading (whilst P3 records at 40Mb/s though)
    • viewing/editing in a appropriate machine ("new" Mac Pro, 2xD700 graphic, files on SSDbased RAID0), displaying on NEC 4K monitor + 4K TV via HDMI
    • tried to smooth things out in my NLE (Final Cut Pro X), but no success so far :(:
      • time-extending the affected clips with "optical flow" method
      • motion and shutter stabilization, even with everything maxed up
    I still have to try to (possibly??) reduce bitrate switching to PAL 24 FPS and/or record in MP4.

    Bottom line:
    • any way to PREVENT my P3P to record jerky footage? (and, yes, still recording in 4K ;)
    • any way to FIX affected clips?
    Counting on you guys ! :cool:

    Thanks in advance

    Cheers
    fabbio
     
  2. Cale262

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    I've been reading about others having the same issue when panning with OSMO but only when using Final Cut Pro X...
     
  3. fabbio

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    Unfortunately we are talking about not edited clips right out the card :cry:
     
  4. bobomet

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    I don't know enough about your camera movements, but always shoot video with VERY slow moves.
    Check the forum for post about camera settings for video, focusing on dampening your yaw and gimbal movements.
    Slow and smooth movements almost always yield smooth output.
     
  5. bobomet

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  6. fabbio

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    Thanks bobomet,
    this happens also with very slow movements but, still, it appears to be "random"

    I'm genuinely convincing myself that this is a P3P's camera problem: when a scene is extremely complex and you're panning, then it's not able to catch and save all that "info" in the SD card.
    However, don't have any answers yet :angry::angry:
     
  7. fabbio

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    Oh ... and that's an example. Since the very beginning of it ...



    Hope you guys enjoy Rammstein ! :cool:
     
  8. Cale262

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    Good video... and yes I do like Rammstein ;)
     
  9. WetDog

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    This seems to show up with dramatic changes in frame to frame information. Like panning at 4K / 30 fps. That puts an enormous strain on a camera / buffer / card write system that is really pretty marginal. I've seen in in my videos and just accept it as a limitation of the craft. I have lenses that cost more than the entire Phantom so I'm pretty careful to temper my enthusiasm. That said, for the cost and capability, it's pretty amazing.

    All cameras are compromises. An Arri Alexa probably would not have that problem but you would need a $20,000 UAV to get it airborne. You just have to know your equipment and shoot accordingly. If your scene needs rapid panning, you probably aren't interested in minute detail and you can shoot at 1080 / 60 or even 720 and get perfectly acceptable images. If you need 4K detail and rapid panning, go rent an Arri or whatnot (or even a GoPro, they do a bit better).

    The one addition I've not seen for the Phantom is a high quality camera (better than the Inspires). It can be done, just would cost a bunch of money. Hopefully, as time goes by, the electronics for this will get cheap enough to trickle down. Meanwhile, enjoy what you can do today.
     
  10. sbarton

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    What SD card do you have is it a high speed U3? Also 4k is limited to 30fps so if you are panning or moving quickly you could get blur or stutter.
     
  11. m0j0

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    I will say first there is noting wrong with your cam. The cameras on the phantoms have fixed apertures. Which means you can't control the light by closing the aperture. Truthfully the proper way to control light for fixed aperture cameras, like the one on the Phantom, is with an ND filter. Without an ND filter you have to use the shutter speed setting to control light and that will result in choppy video because you have to set it very high to reduce the light.

    Simple Answer:
    Shutter settings for your cam should be 2X the framerate. If you are shooting 30fps the proper setting for the shutter is 60; 24 fps = shutter 50, 60 fps = shutter 120 Without ND filters in regular light you would have nothing but completely overexposed video using the correct shutter speed. So to fix your issue get some ND filters. If you cant do that right away shoot when there is less light and at higher framerates to minimize the stuttery look.

    From an article:
    Why Shutter Speed Matters With DSLR Video

    To achieve a film look (which has just enough motion blur between frames to look natural without being “smeary”) you need to follow the 180 degree rule which, simply put, says that your shutter speed should be double the frame rate. This is one of those times when I want to say “don’t worry about what it means, just go with it” as the technical explanation is quite…well…technical. Tyler Ginter did a really good job explaining the technical side of this on his blog post 180 Degree Shutter – Learn It, Live It, Love It.

    While I am not going to try to explain the whole 180 degree shutter concept, I will instead just jump into what it really means to you and your video.

    Since we already know that when we are shooting stills with action, a slow shutter speed will have motion blur and a fast shutter speed will freeze action. When we translate this concept to video, a slow shutter speed will create a smeared look to the video. If the shutter is too fast there isn’t enough motion blur to smoothly transition from frame to frame causing a stuttering or staccato effect. If you have ever looked at something moving with a CRT monitor behind it you will know what this stuttering can look like. Sometimes, this can be used for creative effect like in the opening of Saving Private Ryan.


     
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  12. m0j0

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    Yep and 24fps on the highest setting. Still I am willing to bet that his shutter is set really high which will absolutely make the video stutter.
     
  13. fabbio

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    Thank you all, Dears

    @WetDog: it seems you're confirming what I heard about ... not having an ARRI :)) It's just a matter of scene complexity. Do you think reducing frame rate from 30 to 24 fps could in some way limit this phenomenon to occur given the less amount of data per second to be processed? BTW: interesting your suggestion to shoot panning scenes in 1080p, however it will require a lot more planning. GoPro? Before my P3, I had an heavily customized hex F550-like with a GoPro 4 black (who decided to commit suicide, by the way) and I had the same problem, sometimes, in the very same scene types. At that time, I did't optimized gain and yaw for filming though, so it was partially my fault (I was always too fast)

    @sbarton: I don't have it with me now, but I've personally checked sustained transfer speeds of 20MB/s, so it's like 160Mb/s or maybe something less but surely far faster than the P3P's 40Mb/s max transfer rate. So I'd exclude memory cards from equation

    @m0j0: many thanks, I'll try to stick with this rule from now on. There is a big "but" though: I had stuttering also in dark panning scenes (but still with high complexity, as you can see from the 2nd scene of my video). So, according to logic, at that precise moment my shutter was working with slow times (it was dark), thus my stuttering wasn't induced by shutter high speeds at all ! :pensive: But please correct me if I'm wrong

    Now: is there a way to somehow correct the "affected" clips other than the ones I've already tried ? Please, don't even name trash bin ! ;)

    Cheers
    fabbio
     
  14. TheRealNick

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    @fabbio sweet video! I could see it but maybe only because I was really looking for it. Right around 2:40-2:45 there is a good example, I played it a few times to make sure it was at the same spot. I don't think filters would help with that although that bike wheel video made me put some filters in my Amazon cart! Was that in original footage or perhaps an artifact from editing? I am not sure how to fix it given what you already tried...did you try the memory card that came with it?

    Here is a flight I had recently for comparison with stock memory card no filters...I can not edit yet...old computer...

     
    #14 TheRealNick, Jan 22, 2016
    Last edited: Jan 22, 2016
    fabbio likes this.
  15. With The Birds

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    As said above 4k at 60mbs is a big ask, something has to give. The dji zenmuse does 2.4 Gbps in 4k raw. Gives an indication of how lossy the compression must be at 60mbs.

    Complex scene moving past the lens neans a lot of pixels changing values in a given time interval, something has to give.

    Apparently the hardware is capable of a comfortable 240mbs.

    Im not big on conspiracy theories but i do get auspicious occasionally. Might it be DJI delibearely throttled down so they can charge more for a higher end camera that is nothing nore at their end than a software uodate? Or did they enter an agreement with whoever designed and manufactured the camera for them to limit the bitrate to maintain market differentiation?

    If your interested there is a petition seeking upped bitrate.
    DJI: 100Mbp/s bit rate for the Phantom 3 Professional

    My samsung phone does 4k at 48mbs and looks only slightly worse than the phantom (24fps).
     
  16. WetDog

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    I doubt this is a consipiracy. It's just that DJI is trying to cram a whole lot of a bunch of things in a small, cheap package. Something has to give. This will get better as 4K video and support chips ramp up over time but for now, I think you just have to realize the limitations of your gear and work with it.

    Fabbio: 24 fps is going to give you more blur and maybe push the video transfer subsystem a bit less - you just have to test it. It's actually an easy test and IF IT EVER STOPS RAINING I'm tempted to try it myself:

    Bring the Phantom up a comfortable distance in a safe spot. Contact the relevant authorities, your spouse, your dog and make sure your battery is fully charged...

    1) Start a 4K / 24 fps - do a very slow pan, then an intermediate and a faster pan
    2) Switch to 4K / 30 fps and repeat
    3) Switch to 2.7 / 30 - and you get the idea.

    You could use Autopilot to make a script to keep your pan speeds consistent (extra credit).

    This is how pros do it. They will spend days playing with gear to make sure that they can get the shot the way the director wants it. That's why there is so much pro gear and it is so expensive. Yes, they make it look easy - pros usually do that.
     
  17. fabbio

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    Hi there,

    @WithThe Birds: I'm prone to agree with you ... maybe even signing the petition :cool:

    @WetDog: thanks, that's the best approach we could use. Unfortunately here in Singapore rains every day in this season, besides I caught some nasty virus that is giving me fever and cough (... I suppose whilst filming my video above hahaha:tongueclosed: ) but I do want to test some combinations ! I'll update you guys as soon as I'll be able to fly, but I do hope 4K 24fps will work (fingers crossed)

    Have a great we !

    fabbio
     
  18. With The Birds

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    The chip in the p3p is capable or 240mbs.
     
  19. m0j0

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    To answer your questions about the video remember that filming at a lower framerate calls for slow pans. If there are going to be faster movements and you don't want the "filmic look" go with a higher framerate.


    Phantom 3 Pro / iPad Air 2
     
  20. WetDog

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    It's more than just that chip, however. I don't think it's very clear why the bitrate is so slow. IIRC, the Inspires have that same bitrate. If DJI was capable of pushing more data through the system, you'd think they would give the Inspire's a boost over the Phantoms.