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1080p 120fps looks upscaled?
5451 34 2018-2-9
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Tadango
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I did a quick video in 1080p 120fps but when i play it back it looks like it is upscaled? The file resolution is 1080p but the image certainly does not. I run the latest firmware.....

I will grab a frame from the video and post it here later.
2018-2-9
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Tadango
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See this example:
2018-2-9
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Wachtberger
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Taking a frame from a video cannot reflect the real image quality from my little experience. Please do a video that you can share with us, then we'll get an idea.
2018-2-9
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Tadango
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True, but you can clearly see the scaling in the edges on the fence.

I will upload the video also.
2018-2-9
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hallmark007
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Tadango Posted at 2018-2-9 14:27
True, but you can clearly see the scaling in the edges on the fence.

I will upload the video also.

Watchberger is right this is not a true reflection.
2018-2-9
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Tadango
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It might take a while longer for the 1080p version to be visible.
2018-2-9
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Tadango
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Any comment from DJI?
2018-2-11
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joe_gadget
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Don't think that's an upscaling artifact. Looks similar to the issue on the Mavic Pro at higher than 30fps. If so then that's a camera hardware thing.
2018-2-12
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AIister
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probably anti aliasing.

2018-2-12
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No Man's Drone
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1080p at 120fps runs at much lower bitrate than 60fps.
2018-2-12
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Tadango
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No Man's Drone Posted at 2018-2-12 15:55
1080p at 120fps runs at much lower bitrate than 60fps.

Only a bit less, but that should not produce this kind of image. The overall resolution just feels low.
2018-2-12
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Montfrooij
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Looks similar to what the iPhone SE does.
Upscaling a bit...
2018-2-12
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Tadango
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I just found the same sawtooth in a panorama photo in the Jpeg conversion. The RAW photo's were great so effect must be in the compression engine in the Air. It must be a limitation of the processor or the software. Maybe it can be improved.
2018-2-23
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Malakai_UK
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What you are seeing is pixel binning when you capture at 120fps. This is a process that allows the camera to capture at higher framerates at the expense of some resolution but still outputting at 1080p. On the first gen mavic pro, 1080p@60fps used pixel binning and it looked terrible. The latest gen (platinum and mavic pro built after the platinum) only use pixel binning at 1080p@96fps. Its used by most consumer cameras to get those higher frame rates. I'm not surprised to hear its happening with the air with the higher frame rates. Just glad its not happening at 60fps.
2018-2-23
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Montfrooij
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Tadango Posted at 2018-2-23 00:48
I just found the same sawtooth in a panorama photo in the Jpeg conversion. The RAW photo's were great so effect must be in the compression engine in the Air. It must be a limitation of the processor or the software. Maybe it can be improved.

That should be a different issue.
The up scaling process should not happen with stitching pano's.
2018-2-23
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Tadango
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Thanks for the explanation.
2018-2-23
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Mike12345
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I didn't want to believe it... so I bought  a Mavic Air and tested it for myself, here are two full res screen caps at 1080: 24fps and 120fps.  The 120fps pic definitely has less detail and a lot of antialiasing effects.  

DJI Thor, is this something you guys can fix via firmware?

24fps:


120fps:
2018-3-31
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HedgeTrimmer
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Tadango Posted at 2018-2-9 14:38
https://youtu.be/pWfN2czvjB4

It might take a while longer for the 1080p version to be visible.

I can't get 1080p @ 120fps video to play right.  Even doubling playback speed, the people look like they are in slow motion.
2018-3-31
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Tadango
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HedgeTrimmer Posted at 2018-3-31 22:04
I can't get 1080p @ 120fps video to play right.  Even doubling playback speed, the people look like they are in slow motion.

Play it at 4x speed ;)
2018-3-31
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HedgeTrimmer
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Tadango Posted at 2018-3-31 23:31
Play it at 4x speed ;)

If it were possible...
2018-3-31
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Tadango
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HedgeTrimmer Posted at 2018-3-31 23:43
If it were possible...

You must edit that in post.
2018-4-1
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0Kajuna0
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As Malakai_UK said, that's not upscaling but pixel binning. The Mavic sensor is about 12megapixels, but for 1080P you just need 2MP. What they do is they only read about 1 in 6 pixels from the sensor and skip the rest. That creates aliasing and moiré (contiguous pixels not aligning well) https://en.wikipedia.org/wiki/Aliasing

Camera manufacturers have two ways of dealing with this.
1- Read the whole sensor and, so to speak, produce a new average pixel for every group of pixels you want to downscale. That requires lots of processing power, so it is not always possible on high framerates.
2- Read the center of the sensor only. A portion that matches your target resolution (2MP). That has the side effect of changing the apparent focal length (lens angle), which is why it's my favourite approach. You get two 'lenses' with just one. Of course, most consumers won't like the 'size' of their image changing when in slow motion, so I understand why DJI does not do this, but that's what more professional cameras like Sony's a7sii do.

Even promotional footage at 120fps looks awful (2:45), so that's what we got unless DJI decides to change this via firmware update

A more guerrilla way of dealing with this could be to de-focus the image before it hits the sensor. If you blurry the pixels just enough for them to look like their (6 or so) neighbours, aliasing should not occur. The Mavic Air has a fixed focus, so the only way to achieve this would be to add a blurrying filter on top of the lens. It's probably incredibly difficult to make one that does not destroy sharpness completely, but maybe there's a business opportunity there
2018-4-1
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Mike12345
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The thing that surprises me the most is how difficult it is to find anything on this issue.  FStoppers merely says "Strangely, the 1080 at 120 fps doesn’t crop but the video quality is so bad that I would never use this setting."

Anyhow, I seriously hope that DJI can update firmware to read the center of the sensor for 120fps!
2018-4-1
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KREMi
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looking at speed DJI is doing updates (aka SDK for air...) we might get really old before they do it
2018-4-1
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Tadango
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Mike12345 Posted at 2018-4-1 08:38
The thing that surprises me the most is how difficult it is to find anything on this issue.  FStoppers merely says "Strangely, the 1080 at 120 fps doesn’t crop but the video quality is so bad that I would never use this setting."

Anyhow, I seriously hope that DJI can update firmware to read the center of the sensor for 120fps!

But that would mean a zoom.... And that is what we want as an option anyway
2018-4-1
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fans701299a2
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Mike12345 Posted at 2018-3-31 21:28
I didn't want to believe it... so I bought  a Mavic Air and tested it for myself, here are two full res screen caps at 1080: 24fps and 120fps.  The 120fps pic definitely has less detail and a lot of antialiasing effects.  

DJI Thor, is this something you guys can fix via firmware?

to get 120fps the camera is only reading half the lines and probably only a quarter of the pixels on the sensor, so the image is soft and has a lot of aliasing.
Stick to 4K 30p
2018-4-1
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HedgeTrimmer
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0Kajuna0 Posted at 2018-4-1 02:43
As Malakai_UK said, that's not upscaling but pixel binning. The Mavic sensor is about 12megapixels, but for 1080P you just need 2MP. What they do is they only read about 1 in 6 pixels from the sensor and skip the rest. That creates aliasing and moiré (contiguous pixels not aligning well) https://en.wikipedia.org/wiki/Aliasing

Camera manufacturers have two ways of dealing with this.

would be to add a blurrying filter on top of the lens

Wasn't there an Old-School method of doing that?  
Something like - Nylon stockings pulled tightly over camera lens or stretching clear plastic wrap over camera lens, then smearing very light amount of vasoline on plastic wrap?
2018-4-1
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Tadango
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fans701299a2 Posted at 2018-4-1 09:44
to get 120fps the camera is only reading half the lines and probably only a quarter of the pixels on the sensor, so the image is soft and has a lot of aliasing.
Stick to 4K 30p

That is not an option for slow motion shots of course
2018-4-1
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0Kajuna0
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HedgeTrimmer Posted at 2018-4-1 11:41
would be to add a blurrying filter on top of the lens

Wasn't there an Old-School method of doing that?  

Yes, something like that could be attempted, but the line between improving the image and ruining it will be very very thin.

I own a Pro, so I'll test if defocusing a bit makes a difference in 60p
2018-4-1
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0Kajuna0
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Here's my test (I meant 96P). I see some improvement in aliasing (look at the balconies, windows...) but nothing spectacular. Worth doing it on the Pro, but probably not worth spending time or money on a defocusing filter for the Air

2018-4-2
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Mike12345
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I have started a support case with Rickson at DJI... he seemed surprised and asked for samples.  Will be interesting to see how he replies.
2018-4-3
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Tadango
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Let me guess: This is normal
2018-4-3
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GuLe
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mm, just found this topic and fortunately im not the only one. Just bought a mavic air and also little bit disapointed about the 120fps setting. Also my video's shot in 120fps looks "grainy".
Hopefully they will come with a software update or so….
2018-6-8
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thebmv
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Nice to know that I'm not alone. So, what official DJI support answered?
2018-7-9
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Mike12345
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Never got a response back from DJI engineering.... customer service fail.
2018-7-30
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