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What video delay does a functioning light bridge have

Discussion in 'Pro/Adv Discussion' started by Jase, Aug 6, 2015.

  1. Jase

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    Hi

    I have a P3P running an Android device. The video is working fine and not breaking up or anything. The problem I have is if I put my hand in front of the camera and make a movement, open or shut it etc... the picture on the DJI app is delayed by about 0.5s when I tested with a stop watch. This is with all the advice from this forum on turning as much as possible off, clearing the cache, restricting data in the backround, flight mode on, all the recommended stuff on the DJI app etc..... The only thing I havent done yet is roll back the Google Play Store to the previous version.

    This is a problem for me as with my P2 and 5.8 vtx I could create some amazing videos for my clients flying accurate FPV and now with this delay I battle when close to objects or trying to do super smooth video in following straight lines or accurate rudder control when orbiting subjects.

    What delay should there be with a perfect setup using this light bridge system? Please check because I have had 2 people tell me their setup has no lag but when I tell them to show me hand test it does have lag.

    Thanks for any help
    Cheers
    Jason
     
  2. RoyVa

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    Jason any time you are doing video and it's being transmitted via Lightbridge or wifi there is going to be some lag. It's not much but what the camera sees and then has to transmit takes a little lag to rebroadcast if that makes sense. Even realtime broadcasting from TV stations and their remotes has a little lag. Just the nature of airwaves having to transmit signals.
     
  3. Dome

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    There's no way to avoid lag... It is related to many factor on the tx side and on rx side. Lightbridge is averaged to 200-250ms. That's a good result on a digital radio system.
     
  4. Jase

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    Hi RoyVa

    I'm trying to get a comparison to lets say the 5.8ghz system. I flew that FPV with no issues and now it feels like it reacts ages after I put an input in. I'm sure the 5.8 had lag or latency as well but in micro seconds. The Lightbridge is basically half a second delay, surely that cant be acceptable. With all the nice features of the DJI app I would rather go back to 5.8 or 1.2ghz if I cant get a feel of real time when I'm flying FPV. Are you saying this is not possible?

    Thanks
    Jason
     
  5. Jase

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    Thanks Dome

    That's the information I needed but didn't want to hear :confused: I have been hoping that I might find a solution but if that's it then I will have to try make another plan. The lowest video transmission you can select on the DJI pilot app is 4mbps, if DJI allowed for a lower resolution on their app would that help? Lets say 1mbps?

    5.8 and 2.4 are not as clear as Lightbridge but were perfectly good enough to see and fly in real time. Maybe DJI could make a plan for us and allow a selection of a lower transmission quality to have a more real time for low and close FPV

    Thanks Jason
     
  6. Dome

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    The lagging is a direct function of the bandwidth of the signal. The frequency band isn't responsible, but you can't operate a video tx/rx system on bands below 900mhz due to high bandwidth requirements. If you need 0 lag you need analog tx system.
    On the other hand lowering resolution and than sample video time and than packets to tx, you can have better results, but not less than 100-150ms (I haven't tested this)
     
    Bret Lucas likes this.
  7. Jase

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    Thanks again, appreciate your help
     
  8. tcope

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    I don't think 1/2 second lag should affect obtaining video.... it's quite low. Jump to 1:06.

     
    louforgiveno likes this.
  9. louforgiveno

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    Yup latency as high as .500ms is acceptable....I'd say mine is about 300-350ms.....not mad at all
     
  10. Jase

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    Hi tcope.

    Half a second delay if you flying high with nothing around and doing very basic aerial video is not a problem. If you doing low level FPV between rows of trees or orbiting closely around objects and trying to keep it smooth and perfectly framed then half a second is like a life time. It makes a massive difference. Imagine driving your car and your eyes are only giving you the information of whats happening on the road half a second later. The analogue vtx is much better for that application, even with a lower quality video link being transmitted I could give my clients some stunning professional video. Don't get me wrong I think the P3P is a fantastic machine but wish they had left the 5.8 vtx system in there.

    Cheers
    Jason
     
  11. Dome

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    uhh ... half second delay to me seems really high for P3 ... I never faced this lag, using ios devices (ipad air and 6+) i get ~250ms (on 3 different P3, on ground few feet away).