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Android FPV lag enhanced by P3 GPS processing...?

Discussion in 'Pro/Adv Discussion' started by n6vmo, Jun 20, 2015.

  1. n6vmo

    Feb 26, 2015
    Likes Received:
    Lompoc, CA.
    I have read some reports of direct correlation between the number of GPS satellites acquired by the P3 and the FPV lag/freeze/stutter issue. My FPV lag/stutter issues happened with FW version 1.1.9, FW 1.1.8 ran great.

    This morning I tried a test using my P3A and a Samsung Tab 4. The P3A, RC and DJi Pilot app are at current released version levels. Google Play services disabled, all other apps stopped. Video down-link bandwidth at 4MbS. Video cleared and cache 'off'.

    I placed the P3A on a table, inside my home. Started everything I as would for any normal flight op.
    The P3A acquired between 11 and 13 GPS satellites. Then I moved the camera gimbal throughout its elevation limits and observed the FPV video results.

    I quickly observed a very noticeable FPV lag/stutter. Placing my hand over the GPS receiver of the P3A, the GPS satellite count went to zero and the FPV lag/stutter all but disappeared. Removing my hand from the P3A, the satellite count went back up over 10 and the FPV lag/stutter returned.

    I can only imagine that the FPV lag/stutter would increace if this test had been performed outdoors and 17 or 18 GPS satellite had been acquired.

    To me, it appears that the P3A processor is overwhelmed processing large amounts of GPS data. I am almost positive that GPS processing take priority over other processes such as FPV video streaming.

    Attached is a video of this mornings test.

  2. Meta4

    Meta4 Moderator
    Staff Member

    Jan 8, 2014
    Likes Received:
    That sounds dubious and is likely to be a coincidence.
    GPS processing is done in the GPS chip and shouldn't have any impact on anything.
    It does the calculations and sends updated positions to the Phantom regardless of the number of sats.
    AmosMoses likes this.
  3. 4wd


    Mar 31, 2014
    Likes Received:
    North York Moors
    I've seen other videos showing the same thing, has to be some correlation.