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Very poor video quality with strong signal and high bitrate
4309 20 2020-4-16
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dr_jon3s
lvl.2

United Kingdom
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Hi all, I'm having an unexpected issue with the DJI FPV system where I'm experiencing very poor in goggle quality video with an apparent solid signal - for example the last line of my .srt from a flight ealier reads:
>> signal:4 ch:1 flightTime:225 uavBat:20.4V glsBat:10.6V uavBatCells:6 glsBatCells:3 delay:28ms bitrate:25.4Mbps rcSignal:4 <<

The image becomes extremely pixelelated within a few metres within the focus mode screen edges. At around 20m the centre of the screen also begins to degrade with pixelation becoming very apparent and the image starting to blur out.

Timer is counting, and I'm getting the 'unlocked' transmisison power notification in goggle as I arm.

Disabling the auto temp control does not make any difference and unexpectedly nor does altering the output power from 25mw right up to 700mw.

I'm on 6s with a 25v 1000uF cap on a Holybro Kakute F7 HD stack. Also to further attempt to minimise EM noise I've now run the camera coax cable as far away from the FC as possible - thios had again made no difference at all.

I'm suspecting I've got a faulty unit at this point but would be interested in any thoughts folks may have.







2020-4-16
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arnasnn
lvl.4

Republic of Lithuania
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You sure all the antennas are connected properly ? They need some force to click into air unit
2020-4-16
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Tom_A
Captain
Flight distance : 899951 ft
  • >>>
United States
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Did you take the protective film off the goggle lenses? Have you tried different channels? I would also experiment with different settings. Try high quality mode, set focus mode to auto or off.
2020-4-16
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dr_jon3s
lvl.2

United Kingdom
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Thanks for the replies but yes the antennas are clicked in securely and in fact locked  into place with a printed support. Antennas are also around 50mm apart at the ends.

Film is off in the goggles and the quality mode does make a marginal difference but its still pretty terrible. Focus mode off makes the entire screen more blurry / pixelated.

What I discovered in further testing today is the problem only manifests where I'm flying in grassed areas with a lot of leafy bushes / trees / bushes  around and at distance where id expect to be able to make out a fair bit of detail.

So if I hover and point the camera towards the general greenery then things start to go bad. However if I point the camera in the opposite direction towards paved or bricked areas the problem disappears and I get the quality I'd expect. I also see the difference in output power more clearly in theses scenarios.

Could it be this little unit is just under powered in terms of image compression processing? Is this the Achilles heel of the air unit?  I'm guessing thousands of individual leaves etc require more image processing that say a near uniform view of a wall would be for instance...

If thats the case it would make sense that my signal is full and bitrate is nice an high - the video stream itself could be the problem.

Or alternatively maybe 25.4 mbps just isn't enough the carry the detail - that would make the next firmware update very exciting with the promise of 50mbps birtrate....
2020-4-16
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liboanton
lvl.1
Flight distance : 674757 ft
Russia
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Has absolutely same problem... And I can't catch moment, when its starts...
2020-4-23
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mc54
First Officer
Flight distance : 1030 ft

United States
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I fly in auto focus mode, and I usually get pixelation on the sides even at close range when flying over brush with very similar coloring. I think that's just how the system works.
2020-4-23
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liboantongmail.com
lvl.1
Flight distance : 674757 ft
Russia
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I think 300meters of range is not normally) Few weeks ago system works perfectly and now it’s terrible. I get new air unit and have same problem.
2020-4-24
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fans14253033
lvl.2

Switzerland
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I am having the same problems.
but I realized that I mostly have it when the light conditions get darker.
In full light I rarely have the problem.
I do not really understand why the light conditions have an effect on the pixels?

anyone knows?
2020-4-25
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WeatherB
lvl.3

Canada
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My understanding is that sometimes the 25.4mbps is not enough to transmit all the details in a fast moving scene (such as grass at close range) so the focus mode turns on and you sometimes get pixelation in the centre of the screen as well. I see this happening on mine as well.

Hopefully the upcoming 50mbps firmware upgrade will make this better (assuming that is your problem of course).
2020-5-2
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djiuser_RraAoWLcPSxi
lvl.1

Australia
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Having same or similar issue, been using analog for years so I know a thing or two about how to set up antennas etc, I'm getting sub-standard range. Bitrate definitely drops for me tho, is this the same for anyone else?
2020-5-5
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AbbLabb
lvl.1
Flight distance : 35423 ft

Sweden
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Can confirm the same behaviour.
Full signal and bitrate but very blocky video. I have narrowed it down to having the sun in front of you combined with tree branches and bushes with similar coloring as stated earlier.
Was worried my air unit is defective, but it seems to be a detail resolve limit.
Hoping for the 50mbit to fix it somewhat
2020-5-12
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cusglider
lvl.1
Flight distance : 4025801 ft
Germany
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I know this phenomenon from programming, when trying to reduce transmitted data. You look at the neigboring pixels and when they are quite similar in structure and color etc, they are processed as 1 thereby reducing the amount of data to be processed and transmitted. My guess simply is that DJI is using a similar algorithm.

If I am not mistaken this only happens with the data transmitted to the goggles, whilst the air unit records nicely with all the details. Looks like we have to wait and see DJI work on their algorithm in use to transmit the live feed to the goggles.
2020-5-12
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rushproject
lvl.1

United States
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Same issue here, lots of pixellation and artifacts when flying over grass/trees. Affects both fpv feed and video recorded on the air unit. On the unit video recording stops randomly within first 90 seconds of flight.

Amount of pixelation in fpv feed renders the whole system useless and dangerous, as
-- field of view becomes very narrow across horizontal axis (right and left margins are essentially smudged with pixelation in focus mode),
-- video quality in central area drops to the one of analog vtx feed, while featuring irregular latency

Feels like digital TV with poor reception, but it happens when you operate a half pound aircraft cruising at 60mph - I guess I have to wait for 50mbps upgrade, or introduction of low res mode, or both.

The only good thing so far is when the quad lands in the grass, both fpv feed and recorded footage are gorgeous

2020-5-18
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Tomasimo
lvl.4

Republic of Lithuania
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AFAIK most people here are describing a limitation of 25mbps bitrate.
25mbps is not enough to transfer so much raw image data, so compression algorithms are used. When the image is quite static, it is enough bandwidth to update everything, because most of the image is reused frame to frame.
When all the grass and leaves are moving at the same time 25mbps is just not enough to get 720p@60hz or more, and algorithm can't reuse almost anything between frames.

50mbps would almost entirely cure it.
2020-5-20
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rushproject
lvl.1

United States
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Tomasimo Posted at 5-20 10:29
AFAIK most people here are describing a limitation of 25mbps bitrate.
25mbps is not enough to transfer so much raw image data, so compression algorithms are used. When the image is quite static, it is enough bandwidth to update everything, because most of the image is reused frame to frame.
When all the grass and leaves are moving at the same time 25mbps is just not enough to get 720p@60hz or more, and algorithm can't reuse almost anything between frames.

No, 25mbps is not the only issue. The radio link bandwidth is not applicable to the on the unit recording, yet the recordings are full of pixelation, artifacts and frozen segments of the frame. That means onboard cpu fails to process the data it gets from camera locally.

I am afraid the only way to make the product usable is to introduce yet another "ultra low latency" video mode with lower resolution and frame rate.
2020-5-21
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nullx8
lvl.4
Flight distance : 383635 ft
Thailand
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rushproject Posted at 2020-5-21 13:31
No, 25mbps is not the only issue. The radio link bandwidth is not applicable to the on the unit recording, yet the recordings are full of pixelation, artifacts and frozen segments of the frame. That means onboard cpu fails to process the data it gets from camera locally.

I am afraid the only way to make the product usable is to introduce yet another "ultra low latency" video mode with lower resolution and frame rate.

Yep, sadly that is not an option, setting it down to 702p raises the framerate to 120 AND you not get sound anymore.
3-20 03:35
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djiuser_kBUsDWVBiwua
lvl.2

Canada
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any updates to this im also getting this and its kinda annoying when racing
4-12 12:32
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djiuser_LF7hqZgTsXsA
lvl.1

Canada
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try different channel
5-23 23:15
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djiuser_LF7hqZgTsXsA
lvl.1

Canada
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Tomasimo Posted at 2020-5-20 10:29
AFAIK most people here are describing a limitation of 25mbps bitrate.
25mbps is not enough to transfer so much raw image data, so compression algorithms are used. When the image is quite static, it is enough bandwidth to update everything, because most of the image is reused frame to frame.
When all the grass and leaves are moving at the same time 25mbps is just not enough to get 720p@60hz or more, and algorithm can't reuse almost anything between frames.

how do you set it to go to 50 mbps?
5-23 23:16
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MarcelN
Captain
Flight distance : 2283560 ft
Netherlands
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In the goggles
5-24 00:40
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teddy_striker
lvl.1
United States
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I think it's mostly a matter of how efficiently the view can be compressed.  Without the luxury of multiple passes or gpu levels of processing power like you could do on a computer they're stuck on a platform with limited resources and also a very low latency requirement and limited bandwidth (especially 25mbps).  So when you're flying in an area with lots of movement on the screen it's going to suffer one way or another compared to how it works in more favorable conditions (the closer to a still picture the better).
6-26 15:22
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