Lag between FPV and actual position in the sky of the P2v+

[Dartmoor Dave]

There is a discussion on the fpv thread from a guy asking about lag between fpv and the actual flight position and view and also on a good phantom to go for to use with goggles as he was thinking of buying both. He has received some info on best camera/phantom and goggles but next to nothing on any possible lag between fpv and the phantom particularly for the P2v+, apart from a brief comment from me about there being no discernible difference in lag whether the phantom is a couple of metres away from home or a few hundred metres away. I'd checked that by synching the videos at the start of a flight from fpv on vision app and the camera video in a composite videos and the pair remained in sync for the whole flight.

See
http://youtu.be/tx2goZRycRU


Someone on the fpv thread suggested asking the question about lag on this forum as it was a lot more active than the fpv and that he might get a response.
So here goes, let's see if any expert on this forum has done some work on the lag question and can enlighten the rest of us.

 

[happydays]

Re: Lag between FPV and actual position in the sky of the P2

viewtopic.php?f=27&t=31098

About four posts down.

 

[Dartmoor Dave]

Re: Lag between FPV and actual position in the sky of the P2

Yep Happydays thanks for pointing that out. Glanced down but just didn't notice that Messiry had taken the advice about asking on this thread, hadn't been on the dark stuff either, too early in the day.

Better twice than not at all though. If the Admins want to merge the two then please go ahead.

 

[rstekeur]

Re: Lag between FPV and actual position in the sky of the P2

I've been flying FPV for going on 2 years. I have little time flying with a monitor, almost all my flight time is with using goggles. I just got my PV2+ and am having a difficult time getting used to flying with a phone. I find it very distracting and I don't feel secure flying this $1300 quad streaming video via a WiFi to my cell phone. I'm not saying it isn't good or is unreliable, I'm just very nervous taking my eyes off the quad to look at the phone. I expected there to be a lag in the WiFi video, and I'm glad to see from your youtube video that there really isn't much detectable lag. I think part of the problem is even with a sun shield the phone is not the easiest to see in the daytime. Anyone have any advice on overcoming my phone phobia? I love the quad it's fly's great. I've got a Phantom 1 that I have a immersion 600mw 5.8 vtx on I fly all the time.

 

[CityZen]

Re: Lag between FPV and actual position in the sky of the P2

To pin the delay down better, you need to show 3 things:
1) Phone/tablet view
2) FPV monitor view
3) camera showing the actual Phantom as well as those 2 other views simultaneously.
You should set this up with the Phantom just hovering in front of the 2 displays. Then just yaw the Phantom quickly left and right a bit and you can see:
1) the Phantom itself yawing
2) a fraction later the Phantom view yawing on the FPV screen
3) a fraction later the Phantom view yawing on the phone/tablet

 

[Dartmoor Dave]

Re: Lag between FPV and actual position in the sky of the P2

I agree with CityZen that the synchronised fpv and copter camera views doesn't show there is no lag. All my composite video shows is that there is "no change" in lag whether the P2V+ is a couple of metres away from the RC or 250 metres away. What I do in getting the composite view is to adjust the timing of the two videos in my video editor so that they are aligned at the start of the video and then they remain aligned throughout the video of the flight

I've been trying to think of a way in which any delay could be detected and the idea of having a video camera view of the phantom in the air but also showing the fpv view screen at the same time as CityZen suggests would work. Unfortunately videoing the fpv vision app screen and the copter would be very difficult as it is hard enough for us to see the small screen and getting a video of that screen and the phantom in the air at the same time would be a real challenge.

Although I've not used them, or seen them being used, I understand that Epson Movario glasses enable the fpv screen to be seen with the copter actually also visible in the air. That should enable an estimate to be made of any lag, so I wonder if that has been tested.

Of course then would come the debate as to whether the Epson device introduces lag in its own right.

 

[messiry]

Re: Lag between FPV and actual position in the sky of the P2

Thanks everyone for this discussion. i was also told that it depends on the quality of the video (1080, 720, etc) and if recording is on or off, last thing i was told that it depends if you are using iPhone 5s or 6 then processing is fast and no problem. i think the P2V+ has a kind of semi FPV not a true FPV. i have difficulties to fly this quad and looking to my phone, its so confusing and very easy to lose orientation of directions, plus the sun reflection on the phone make is impossible to see, and many other reasons not sure how you guys feel about it.
thanks

 

[Dartmoor Dave]

Re: Lag between FPV and actual position in the sky of the P2

Following on from Cityzens suggestion about a rapid sideways movement being detectable for lag, I remembered that with the asymmetric position of the camera in the P2V+, a sudden sideways movement of the phantom to the left causes my left side landing gear to come into view on the fpv screen. I tested this a few minutes ago by eyeballing the fpv screen camera, the phantom and the control as I caused the phantom to lurch to the left in my garden (the wind had dropped from 50 kts overnight to 5kts now thankfully).

Visually, the movement of the phantom in the sky and the appearance of the landing gear on the fpv screen appeared instantaneous to the eye so this unscientific test does indicate that when using a modern smartphone ( I'm using a Samsung Galaxy S5 by the way -great screen and very responsive ) the lag is virtually non existent, so I'm quite happy with that.

I reckon this could be repeated with someone videoing the vision fpv screen close up with the phantom also in shot. By viewing the resulting video frame by frame if necessary then a more accurate measurement could be made since we know the frames per second rate and 25 fps is 40 millisecs between frames.

Nice to have a forum like this where we can bounce ideas around (but hopefully not phantoms) and discuss things like this.


Messiry indicated how difficult he found it to see the fpv screen in sunlight and how difficult he found it to judge the orientation of the phantom when it is any distance away. I think that most people find watching the phantom and the screen at the same time quite difficult, particularly when the phantom is some distance away, so he is not alone there. It is not unusual for me to glance down at the screen to check some parameter and then look up again and not be able to see the phantom in the sky. It certainly can put you in panic mode. I'm now not afraid to put faith in the radar and to simply rotate the phantom out there somewhere until the radar shows the radar arrow pointing towards me and simply fly it back towards me, watching the screen and the distance, height parameters at the bottom. I progressed to NAZA M modes so there is also that very useful get you back mode of Home Lock too. Always worth validating that your home point really is home by checking out how the parameters are panning out when you are flying close to take off point.

Also worth remembering that not all screens are equal, I've a 7" Samsung Tab 3 that I thought might be better than the Galaxy S5 with its 5.1" screen. In reality the 7" tablet is awful to view outside compared with the Galaxy. I've also bought a cheap sun cover for the S5 but TBH I very rarely use it, I just up the screen brightness to max and it is reasonable in most conditions

 

[Brent10]

Twice I've experienced extreme lag using an iPhone 4S. A reboot of the phone cleared it up both times.

 

[Mako79]

Place the phantom in front of you and use your hand to wave. Is it laggy on your FPV?
Place your mate and your phantom 250m away and get him to jump. Is it laggy on your FPV?
With the latest firmware and 640x480@15fps, there is minimal lag.