Please select Into the mobile phone version | Continue to access the computer ver.
Android Pilot app findings - FPV lag / overheating / CPU-bound
2165 8 2015-6-26
Uploading and Loding Picture ...(0/1)
o(^-^)o
ScottyT
Second Officer

New Zealand
Offline

My fairly high spec'ed Android tablet gets hot running the DJI pilot app, and it lagged before I reclaimed some resources after employing the Google Play Services workaround.

But it's no surprise it gets hot when the DJI Pilot app sits at > 50% CPU on a quad core @ 1900MHz (not throttled). The temp gets bumped up 30C (86F) degrees at this point
and this is before I even turn on the P3 so the app is using half the tablet's resources before the FPV stream is even initiated. The app is basically sitting there with a black screen showing "No signal".

I also notice consistently high CPU usage, and thus temperature, when the app is simply loading one of my flight records over a wifi connection.

As per the attachments showing Temperature, CPU usage, and the active CPU frequency:-

Pic 1 shows the performance stats for the tablet running the DJI pilot app with the RC transmitter turned on but the P3 is off. Grounded. No blinking lights. No FPV stream to display. Nothing really for the app to do.
However it is using 50% of the CPUs at full frequency, hence the tablet heats up considerably, going from 40C (104F) to > 70C (158F)
Where the red line intersects the graphs is where the RC transmitter is turned off, app still running. Negligible CPU usage by the app, as one would expect (note the frequency stepped down as there is no longer CPU demand).
The tablet cools down. It's 10C (50F) outside - cold. Calm is restored at 40C.

Pic 2 shows the P3 in flight with FPV very laggy. As you can see the CPU usage and Temp are very high. When a temp approx >80C (176F) is reached, the
tablet will throttle the processor as per the frequency graph. You can see the Frequency chart and Temp chart peaks corresponding where it tries to ramp up the frequency again once a little cooler, but it soon heats up and is throttled again. Hence the lag or choppy video.

Temperature is the result of the high sustained CPU usage. Why is there high CPU usage for the app when it is doing absolutely nothing before the P3 is even powered on?

However, I can play a 1080P or 4k video using VLC, and have Google maps running in the background actively using GPS as SatNAV and the tablet is lucky to use 10 to 15% of the CPU resources. Temperature rise 5C, hitting 45C (113F). MAX.
Isnt that basically the main workload of the app aside from the fact it's being done through the USB bus? It acts as a lowly 720p display device for the most part...where's all the overhead?

Be interested to see the findings of others when they monitor their tablet using the "CPU Temp" app, especially to see what the temperature is when you are using your tablet in higher ambient temperatures, for both the DJI Pilot app, and other tasks such as playing movies. Be sure to turn on the 'CPU temp overlay' setting so your temp can be monitored without switching in between apps.

Seriously. People shouldn't be needing to purchase high end tablets with more CPU resources or greater tolerances to cater for this poorly performing app alone, or have to worry about cooling them with home made ice packs. Many seem to be jumping ship to IOS devices as there seems to be less problems with the app there; by all accounts it sounds like it is a CPU hog on IOS so it probably has similar issues.

DJI need to sort this out, as there are obvious inefficiencies at play and I doubt the app really requires all the CPU resources it is demanding.



PIC1-APP and RC ON only.jpg
PIC2-P3 laggy flight.jpg
2015-6-26
Use props
sinbad_uk
lvl.4
Flight distance : 117343 ft
United Kingdom
Offline

I just did a quick test in my house (as its 2am ) just sat with the DJI Pilot App going, RC On, Phantom On.
Bare in mind I am also recording the screen.

Galaxy S5 with Android 5.0
Latest Firmware and DJI Pilot App
Here are the results.

Hope this is helpful...
2015-6-26
Use props
ScottyT
Second Officer

New Zealand
Offline

sinbad_uk@ntlwo Posted at 2015-6-27 09:55
I just did a quick test in my house (as its 2am ) just sat with the DJI Pilot App going, RC On, Ph ...

Cheers. Yeah my One-plus One phone has a more powerful CPU like yours with more CPU cycles to spare (2.4Ghz vs 1.9Ghz in my Samsung tablet), which doesn't seem to heat up as much as a result. Similar temp @50 to 60C but the idle temp for the CPU is 30C.

What does your CPU temp report before opening the app, while it's idling?
2015-6-26
Use props
sinbad_uk
lvl.4
Flight distance : 117343 ft
United Kingdom
Offline

When the phone is idling it CPU temp is 34c and CPU usage is 9% to 16%
2015-6-27
Use props
ScottyT
Second Officer

New Zealand
Offline

Yeah, pretty much the same as my Oneplus One phone. As the S5 (which is suppported by DJI) uses the same high speed CPU/GPU

CPU        Quad-core 2.5 GHz Krait 400
GPU         Adreno 330

I lose the FPV feed and have disconnects with the latest app though. No such problems on my Tab S.
2015-6-27
Use props
tester1
lvl.1

Germany
Offline

I wanted to open up the same Theme. But my post is not unlocked for days...
Thank you that you have the opened Thread. Here is my description:
It would be nice if others can supplement or confirm the description… OR: How's it going on your tab?

-----------------------------------------------------------------------------------------------------------------
I had many flight times with P3 Pro. (FW 1.1.9 Pilot App 1.1.0) – it was fine for me!
After install FW 1.2.6 and Pilot App 1.2.0 & on android 442/444 I got some Problems!
After upgrade my ASUS MeMO to android 501 it got worse:

1a)      Live image stutters and jerk on MeMo Tab (android 4.4.2)
        a.       maybe due to high CPU utilization and overheating (up to 75°C)  (… as already reported by others)
        b.      On android 4.4.2 the Pilot App consumes about 55% of CPU. Together with some google apps the CPU utilization rises up to approximately 80 to 90%)
        c.       sometimes some Google apps or processes are terminated
        d.      Stop Google Play App to reduce CPU load don’t works for me. I had to shut down more apps. (Contacts, Framework, …) but thereby often crashes the pilot App.

1b)      Pilot App 1.2.0 and android 5.0.1: no live Image on MeMo Tab anymore & Pilot App stutters, no tests possible.

1c)      Pilot App 1.1.0 and android 5.0.1: live Image on MeMo Tab is OK, but Pilot App often shuts down and restart during flight, once in a very difficult situation
        a.       The Pilot App on 5.0.1 now consumes less than 37% of CPU! But together with google apps the CPU utilization is still up to 75%
        b.      Now i must shut down googles "Backup-Transport" to reduce CPU utilization
        c.       Five times some google processes were terminated .
        d.      Two times I had some message like: “stop caching video, cache is full?” but “Auto Clean Cache” was enabled (and 8GB free space left on Tab)?

2)      Pilot App 1.2.0 and And Galaxy S3 LTE android (4.4.4):
         a.      Sometimes Pilot App or some Google apps or processes are terminated.

3)      There is also a Distorted cached video in fast moving scenes with all android versions, but all Videos on the memory card are OK!
        a.       On android 5.0.1 there are some pixelation in cached video image which move thru the image
        b.      On android 4.4.2 & 4.4.4 there are green banding & areas.
        -> Example: P3P revolves around its own axis. Every 4-5 seconds a green line appears at the bottom and move thru the image. Then the fault disappears with a stutter
        -> New attempt at home (no flight, only tilting the camera) -> same problem

Test system:
a)      ASUS MeMO Pad 8” (ME581CL), Full HD, 64 bit Intel Quad-Core (1,8GHz), Android 4.4.2 – Now Update to 5.0.1
b)      Lenovo Live-Tab 10,1”, Full HD, Intel Quad-Core (1,8GHz), Android 4.4.4
c)      Galaxy-S3 LTE (Android 4.4.4), 2GB
d)      Phantom 3 Professional, FW 1.2.6, DJI Pilot App 1.1.0 & 1.2.0

Sorry, my English is a little rusty.
regards
2015-6-28
Use props
droneflyers.com
First Officer
Flight distance : 60709 ft
  • >>>
United States
Offline

"Isnt that basically the main workload of the app aside from the fact it's being done through the USB bus? It acts as a lowly 720p display device for the most part...where's all the overhead?"

Well, I'm just a hobby technologist, but I think it is doing a LOT more than bringing in the video!  
Forgive me any of my description errors here because I'm not an engineer.

The older Analog video FPV stuff just sent a stream to the monitors (analog also) which work something like a TV screen - scan lines, etc.

Lightbridge is a digital signal which sends a large stream of raw digital data to the device - not just video that's already been processed (youtube, etc.). The video has to be processed and then rendered. This is why  digital video streams on quads have more lag than analog - time and CPU and GPU power needed on both ends.

One reason - I think - that IOS works better is because there is an option in the DJI IOS app to make use of "hardware decode" in the IOS device. This may show that IOS had some addressable hardware which is probably not available on Android - Android has to use software tricks to do the same thing.

As to people having to purchase high end devices - here is my opinin FWIW.

I started with a $30 Android Moto-g - which works OK. I am now using a Nexus 7 II which also works good enough for my use. So those are 2+ year old devices.

However,  considering that before the P3 we had absolutely nothing to compare (in any way) to this range and video-feed quality, how can we state that an old...or even new..device should work flawlessly? isn't it like other high requirement stuff (OCR, Voice Recognition, video editing, etc.)  where the technology is somewhat ahead of the hardware...or at least requires the best?

As far as high CPU use when not doing anything, I don't think that's an accurate metric. My task zapper program takes up 50% sometimes when I open it an kill tasks....the pilot app is not designed to run without the bird so it could be trying to do a lot of fruitless things.

I'm not claiming that the app cannot be made more efficient. However, the question I ask is whether folks would have preferred that DJI release a less capable (lower res, lower fps, less telemetry, etc.) app to satisfy  everyone? It seems the more we get, the more we want. You would have spend $3500 for the Inspire and a good tablet - now we are complaining about spending $1K and perhaps $300 for one.
2015-6-28
Use props
ScottyT
Second Officer

New Zealand
Offline

droneflyers.com Posted at 2015-6-29 08:41
"Isnt that basically the main workload of the app aside from the fact it's being done through the US ...

Well, I'm just a hobby technologist, but I think it is doing a LOT more than bringing in the video!  

Like what? What is the tablet actually doing?

The older Analog video FPV stuff just sent a stream to the monitors (analog also) which work something like a TV screen - scan lines, etc.

Lightbridge is a digital signal which sends a large stream of raw digital data to the device - not just video that's already been processed (youtube, etc.). The video has to be processed and then rendered. This is why  digital video streams on quads have more lag than analog - time and CPU and GPU power needed on both ends.

So the RC unit does nothing at all in the mix? No smarts...it leaves all processing up to the tablet? And it's a low framerate 720p feed, nothing special. And that's not the reason for the lag.

One reason - I think - that IOS works better is because there is an option in the DJI IOS app to make use of "hardware decode" in the IOS device. This may show that IOS had some addressable hardware which is probably not available on Android - Android has to use software tricks to do the same thing.

All tablets have addressable GPUs. People are turning on hardware decode where once they didn't have to - allegedly since a firmware update. These are all steps being performed because of issues with the app, to claw back resources.

As to people having to purchase high end devices - here is my opinin FWIW.

I started with a $30 Android Moto-g - which works OK. I am now using a Nexus 7 II which also works good enough for my use. So those are 2+ year old devices.

However,  considering that before the P3 we had absolutely nothing to compare (in any way) to this range and video-feed quality, how can we state that an old...or even new..device should work flawlessly? isn't it like other high requirement stuff (OCR, Voice Recognition, video editing, etc.)  where the technology is somewhat ahead of the hardware...or at least requires the best?

No. The bird is off, there is NOTHING to do and is thus not "High Requirement Stuff" - You can't be comparing it to a workload where CPU cycles would actually be required.  People would be understandably upset if their OCR or Video editing app was cooking their devices when it was not actually performing any practical task.

The RC is providing the lightbridge and range, not the tablet. It's a low fps 720p feed, is all...when it's on. It's comparable to anything displaying 720p or higher from a digital format.

As far as high CPU use when not doing anything, I don't think that's an accurate metric. My task zapper program takes up 50% sometimes when I open it an kill tasks....the pilot app is not designed to run without the bird so it could be trying to do a lot of fruitless things.
50%...so, at what frequency step, for how long, how much does it heat up the CPU/Tablet? Describe your metric better. The DJI app has nothing to do with the bird turned OFF.

I'm not claiming that the app cannot be made more efficient. However, the question I ask is whether folks would have preferred that DJI release a less capable (lower res, lower fps, less telemetry, etc.) app to satisfy  everyone? It seems the more we get, the more we want. You would have spend $3500 for the Inspire and a good tablet - now we are complaining about spending $1K and perhaps $300 for one.

No we're complaining because the app is badly coded and even high end tablets are lagging. There's no point buying a Porsche when all you need is a Mini.

2015-6-29
Use props
Dive-N-Dog
lvl.4
Flight distance : 1087028 ft
United States
Offline

I have made my own fix for now. http://forum.dji.com/thread-22240-1-1.html

-Dog
2015-6-29
Use props
Advanced
You need to log in before you can reply Login | Register now

Credit Rules