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Banding on video

Discussion in 'Pro/Adv Discussion' started by DAVEJF, Dec 20, 2015.

  1. DAVEJF

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    First proper flight (IE not in my garden) and I managed to lose sight of my P3a and had a nasty feeling in the pit of my stomach that I had just seen the last of it disappearing beyond the trees. Fortunately, RTH brought it back safely. Anyway, this flight raised two queries that you folks might be able to help with.
    Firstly, the RTH missed the home point by a good 8-10m, is that typical accuracy to expect? If so, that's fine but worth bearing in mind when picking takeoff point.
    The second query relates to the video quality. There is some 'banding' that occurs, which is most noticeable when the P3 is moving (see video link). It isn't too bad but not ideal. Is this usual?

    SkyPixel

    Thanks in advance.
     
  2. Viral

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    8-10 m is fairly close to what you can expect from rth. I would have claimed more like 5-8m from my exp, but close. Keep that in mind when marking an rth spot. However, I wouldn't actually use the rth feature to land my p3 on its own unless absolutely necessary. Use it to bring you bird back to your general location so that you can re establish RC and visual control over her. Then cancel rth and take control manually again.

    As to the banding... That doesn't look normal. Did the footage look like that coming out of the craft? That almost looks like heavy compression from upload to the site. What see your camera settings?
     
  3. DAVEJF

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    Hiya,
    Thanks for the feedback.
    Yes I noticed the banding in fpv during the flight, in fact it was more noticeable then. I haven't changed the camera settings from those preset when it arrived.
    They are as follows: ImageUploadedByPhantomPilots - DJI Phantom Forum1450621303.986740.jpg
    ImageUploadedByPhantomPilots - DJI Phantom Forum1450621323.142799.jpg
     
  4. Oso

    Oso

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    The banding looks to me like prop shadows when you are facing the sun, but I didn't get to watch the entire video. It just kept buffering so I closed it.
     
  5. DAVEJF

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    Hi, I don't think it can be that, as they are horizontal bands scrolling vertically down the entire screen and appeared both when facing the sun and with back to it.
    Thanks for the input tho'
     
  6. WetDog

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    The 'banding' seems to occur when the scene brightness changes rapidly. You are on auto exposure - the camera is going through some wild gyrations to keep everything exposed correctly. Switch to manual exposure and don't rotate into the sun....

    The video seems horribly compressed. Somewhere along the workflow you got into a bad setting. That can also make banding appear worse. Typically banding is due to trying to push the sensor too far - any digital sensor will band if you crank on it hard enough and the Phantom camera, while 'pretty good' is not immune to this at all.
     
  7. DAVEJF

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    'The video seems horribly compressed. Somewhere along the workflow you got into a bad setting. That can also make banding appear worse.'
    Hi wetdog, At the risk of showing my ignorance of such matters, what do you mean by your comment in quotes above?
     
  8. alokbhargava

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    If home point was set accurately with multiple satellites locked and the landing area is free of obstacles, it should land within 10' - 15' of the home point radius. That's my experience. I in fact got much closer. But you get your bird back safely is most important.
     
  9. 480sparky

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    The banding issue might simply be due to the horrible compression.

    Does it show up in the original file? Have you tried another editor?
     
  10. WetDog

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    If you look at the video, the grass in particular has very little definition. It looks like a green carpet. Likewise, the trail. Much of the fine detail is obscured. The Phantom camera is much better than that.

    But there are a couple of steps in between getting the video off the bird and onto the web. You download it to your computer, perhaps edit it then prepare to upload it to the website, in your case 'SkyPixel'. If you look at the file sizes of the video coming off the Phantom, you will see them in the gigabyte range. Should look fantastic on a good monitor. But trying to upload several gigabytes of info to the Internet is often impractical, so the video is compressed. That is, the larger files are made into smaller files. If you are not careful, you can really mess up the image on compression settings. Oft times, you have little control over it - SkyPixel may decide how much bandwidth and disk space they want to allocate to you and that might entail signficant reduction in video quality. In fact, it looks like the video was compressed so it would look OK on a smallish cell phone.

    When you compress the file, you can also exacerbate any flaws in the original video. My guess is that the original issue with the banding is that the camera is trying to adjust the exposure as you rotate into the sun and that when compressed it looks worse that it typically would.

    Look at your original video (from the drone). Does it have the same issues?

    Take another video, this time keep the lens away from the sun. Does it help?
     
  11. DAVEJF

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    The video is what was captured directly to my iphone6 in dji Go. The original footage shows the banding and I was aware of it during the flight when looking at the fpv on my phone. I used the dji go app to create the movie, so haven't yet downloaded it to a PC. I will do that and see if it looks any better. Many thanks for your help
     
  12. 480sparky

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    It's a (very!) low-resoution file that's stored on your phone. The real video is on the micro SD card that's in the bird.
     
  13. DAVEJF

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    Ok, crisis over! The video looks absolutely fine on my laptop reading directly from the micro SD card.
    Thanks guys, your help is really appreciated.
     
    bluer101 and Oso like this.
  14. Dirby

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    i had simelar lines in two video i sent the video to DJI and they told me to send it back to them.
    they will have it in the morning.
     
  15. bluer101

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    I get the same scrolling bands when using the cached video directly in the Go app. None is present in the files directly from the micro sd card from the bird.

    I mentioned this in other threads too. I think it's the way the go app is caching the video within. There is some radio interference with the transmission that would not be present directly off the SD card.

    I wish that I could use the video cached with the internal movie maker to make quick movies. The same thing happens when you lose range or low signal. It will make the cashed video break up to which is really unusable to make a movie within the app.
     
  16. DAVEJF

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    Yes, it is a bit naff. I guess it's ok if you quickly want to create and send a vid. Via Twitter or whatever and aren't too bothered about the quality.