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SCHOOL ME SON, I WANT TO GET MY LEARN ON
1985 16 2015-5-18
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JakeLikesStuff
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United States
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I should start off by saying I am only a hobbyist, and not a professional, so forgive my ignorance or lack of knowledge for anything that follows… but I want to learn…


I’ve been flying my Inspire for about 3 months now. I love it. I can’t get enough of it.


I record in 1080p at 60 frames per second. I never bothered with 4K because I don’t have anything that can display 4K, and I wasn’t sure what kind of a drain it would put on my Mac with video editing.


Also… my workflow is thus… I copy the files from Inspire’s memory card to an external hard drive, I then do a very rough cut of those files using QuickTime Pro’s mini editing/trim option. I save off those trimmed files to a new folder, and then import that folder in to Final Cut Pro, where I edit, and export to a master file, then upload to YouTube.


Somewhere in the process, or perhaps from the very recording itself (I suspect the recording itself) my image seems a little grainy or not crisp. And I’m not exactly sure what I’m doing wrong or how I can correct it. It seems the same quality even when I’m looking at the files directly off the Inspire’s memory card, so I don’t think it’s any of the post flight stuff I’m doing.


My first guess is to record in 4K and downscale in Final Cut Pro to just my normal 1080p, obviously at 30 instead of 60 fps. My thinking being I might get a sharper image that way? Maybe?


If there’s some other settings or something else I should be adjusting or any input at all, I would greatly appreciate it.


Below is a link to the most recent footage I shot, but really any of  my videos on my page (drone ones obviously) would show the same type of thing.





Thank you,

2015-5-18
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PeteGould
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The material looks suspiciously to me as though it's being scaled down and then back up again, so what you're seeing at 1080 resolution isn't really 1080 resolution.  It has been cut to half that and then blown back up again.

I'm very suspicious of this:

I copy the files from Inspire’s memory card to an external hard drive, I then do a very rough cut of those files using QuickTime Pro’s mini editing/trim option. I save off those trimmed files to a new folder


Right off the top of my head I'm inclined to say "skip this step and go straight to Final Cut."  And then ensure you have the correct presets to ensure your edit project is 1080p (so the raw pixel dimensions are 1920 wide by 1080 high, progressive, NOT interlaced).

If you'd like to rule out a problem with the video recording itself, shoot a raw clip of 15 - 30 seconds and post it straight out of the micro-SD card with NO processing or editing, and we'll take a look.
2015-5-18
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Farnk666
Captain
Flight distance : 1711394 ft
Australia
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Yea, what Pete said!
2015-5-18
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JakeLikesStuff
lvl.4

United States
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PeteGould Posted at 2015-5-19 10:48
The material looks suspiciously to me as though it's being scaled down and then back up again, so wh ...

Thank you, Pete. I'm going to try this out. Found some untouched files on my external. Going to important that and a trimmed clip I got from QuickTime and I'll upload the results when I'm done.

Assuming this is the problem (which would be incredibly frustrating since this is what I've done with all my drone videos, and some other non drone videos, up till now)... is there a way to easily and quickly trip Inspire vids before going in to Final Cut... my concern is that importaning multiple 10 clips creates a lot of render time before the files are ready to edit in Final Cut Pro. Can you trim in DJI's Director? I haven't tried that yet (presuming it's on the Android app).
2015-5-18
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bornish
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Flight distance : 91447 ft
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JakeLikesStuff Posted at 2015-5-19 12:31
Thank you, Pete. I'm going to try this out. Found some untouched files on my external. Going to im ...

Hi Jake!
My videos are saved as MP4 instead of MOV, so I am using a little free software to extract cut portions of the original footage shot in any resolution (1080P, 4K 30P, 4K 24P). I am sure there're so many free tools like this one (http://www.videohelp.com/software/My-MP4Box-GUI) for any video format including MOV files. The main reason for using such an utility before any other processing is because these DO NOT re-compress the video file, preserving the exact same bit-rate, resolution, compression, and so on. The second advantage of cutting clips this way is that is the fastest way to do it, as re-compression takes much longer than data copying from source file to destination file as these utilities do. How I believe they work is that they create a new file header defining the cut out portion and then they start copying the compressed data starting with the first index frame required until the last index frame needed to contain the portion selected. That is because most codecs compress video data as more frames in a chunk and not frame by frame.
Thus, this method of splitting / extracting clips from a video file is the fastest and with no quality loss.
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Bogdan
2015-5-18
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JakeLikesStuff
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bornish@gmail.c Posted at 2015-5-19 12:50
Hi Jake!
My videos are saved as MP4 instead of MOV, so I am using a little free software to extrac ...

That's a great suggestion. Thank you. I'm going to need something just like that, but Mac friendly. If anyone has suggestions I'm all ears. Thanks again.

Turns out I don't have any saved drone files. I'd already purged them all.  I'll try and capture something soon though to run a side by side test.

Any and all other suggestions are welcome. Thanks everyone. Love this forum.
2015-5-18
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GrahamJ
Second Officer

Australia
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Good info, thanks fior sharing!  Post, is an area I really can do with as much forum response as possible...
2015-5-19
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PeteGould
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JakeLikesStuff Posted at 2015-5-19 12:31
is there a way to easily and quickly trip Inspire vids before going in to Final Cut... my concern is that importaning multiple 10 clips creates a lot of render time before the files are ready to edit in Final Cut Pro.

There are several issues you can encounter when working with this kind of footage.  In some ways it introduces complications we don't necessarily see in very high end (feature film, episodic television) products, which can be a lot easier to work in but fabulously more expensive.  What I'm about to describe is not unique to the Inspire - it's true across all products at this level.

The most annoying is data compression.  The Inspire saves videos using the H.264 compression algorithm and this is true regardless of whether you save to .mov or .mp4.  Those formats are only the wrapper containing the file.  The file data itself is H.264.  And H.264 is simply a means of reducing the size of the file while retaining as much of the visual content as possible.

Let's talk about the resolution you're shooting in: 1080 progressive.  First, consider the sheer size of the raster we're talking about - 1920 pixels wide by 1080 pixels high.  That's 2,073,600 pixels.  And since each pixel can be any of 16 million possible colors, each pixel requires three bytes of data to represent it - a byte for red, a byte for blue, a byte for green.  So if you multiply 2,073,600 pixels by three bytes, you end up with 6,220,800, or roughly six megabytes.  Per frame.  At 60 frames per second.  Clearly, something has to give here, because that's about 360 megabytes per second.  Imagine the cost of the storage.  Heck, imagine the cost of the electronics that can move and store that much data in real time.  Then think of 4K which roughly quadruples that.  Ouch.

Enter compression schemes.  You know them from photography because if you save something as a .jpg file, the storage requirement is a tiny fraction of what it would be if saved to an uncompressed .tif, .tga or .bmp file.  The idea is to throw away A LOT of data and come up with some way of ending up with an image that looks like the original (but is missing a lot of its actual data).

The problem with compression schemes is that the ones we're discussing here are lossy.  In other words, when you open and read the file, you don't get the whole content back the way you do when you open a .zip or .bin file.  You get a degraded representation of the image that is "good enough to look okay."  If you save in a compressed format, then read the file and do something with it and save it again, it doesn't just save the original data.  It recompresses that data.  And often, the small visual artifacts created from lossy compression get mistaken by the compression engine, the second time around, for image content, so they get exaggerated when the file is saved again.  Do this for a few iterations with a lot of compression added and the file will look really awful.

And video compression, as distinguished from still compression, adds a temporal element.  H.264, like a lot of lossy video compressors, saves a "key" frame at fixed intervals, and then the subsequent frames only save the visual differences between that frame and the immediately preceding frame.  That continues until the next "key" frame.

Now, there are degrees of compression.  You can tell an H.264 compressor how big a file you're willing to live with in exchange for greater quality.  If you compress too little you get a huge file.  If you compress too MUCH, too much degradation occurs before the next "key" frame, so when the video player hits that frame you suddenly see a slight visual "hit."  What you're seeing is more and more compression artifacts collecting over the course of a second or two (whatever the selected distance between key frames happens to be) and then suddenly a much cleaner frame, followed by the increasing collection of artifacts again, over and over, in a continuing rhythm.  In the case of the Inspire, the folks at DJI have set the compressor so it's clobbering the daylights out of the video, and they've provided no user access to the compressor settings to allow us to back off on the compression ratio.  This could be a choice on their part not to give consumers access to advanced controls, or it may be a hardware limitation: the compression settings COULD be set to allow the maximum data throughput the hardware is capable of.  If so, that would be a real shame, because these files are currently way, WAY too compressed.

That's why some people are complaining about a rhythmic disturbance in their videos especially when shooting fine detail, like a field of grass, or a forest of pine trees.  What they're seeing is the degradation over the course of the frames following a key frame, and then - SNAP - a new key frame, and then degradation again.  If you're not accustomed to seeing it you may not initially notice.  Once you're looking for it, it's obvious.

This is my longwinded lead-in to why I don't pre-edit Inspire clips.  Because typically when you do that, the saved edited clips have been recompressed - and there's too much compression to begin with.  I shoot judiciously (or at least I try to) and save the entire raw clip, which is what I use as source.  You can elect to pre-edit and just save "buy" clips, of course.  Usually when people do that, though, they save to a much less compressed target format in order to minimize recompression artifacts.  But then you've lost the storage benefit of pre-editing, because a less compressed format can be ten times the H.264 format per running second of media.  Bornish, in a post above this one, mentions tools that are intended NOT to recompress, but simply to extract and separately save chunks of video with the original compression intact.  I haven't played with any of those tools.  If there are confirmed tools that can extract and save H.264 video data while guaranteeing not to alter that data, that's a good solution.

NONE OF THE ABOVE, however, relates to what I'm seeing in your video, which is that the image has been scaled down and then back up again.  I can only think of two places where that might be happening.  One is in your Quicktime pre-edit pipeline.  If it's getting 1080p/60 as an input, you need to make absolutely sure it's giving you 1080p/60 back out and not some other frame size due to a wrong or corrupted preset.  The second place is in your FCP project.  If the project is DV NTSC widescreen, then the imported 1080p media would have to be shrunk to fit the frame - if the output is then blown back up to 1080p when exported, you'd get what we're seeing in this video.  There may be other ways this could be happening as well, but those two come immediately to mind.  One thing is sure: the Inspire video output definitely looks better than that.
2015-5-19
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JakeLikesStuff
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PeteGould Posted at 2015-5-20 00:22
There are several issues you can encounter when working with this kind of footage.  In some ways it ...

I'm drinking all of this in like a warm comforting tea. Thank you for the educational lesson.
2015-5-19
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PeteGould
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JakeLikesStuff Posted at 2015-5-20 03:14
I'm drinking all of this in like a warm comforting tea. Thank you for the educational lesson.

You seemed like someone who appreciates knowing whys and wherefores.  
2015-5-19
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gixxertaylor
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PeteGould Posted at 2015-5-20 00:22
There are several issues you can encounter when working with this kind of footage.  In some ways it ...

This is a great. I wish we could sticky this in the help section.
2015-5-20
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Dangair
Second Officer

Canada
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Pete, what you described I'm assuming is the rhythmic pulsing stitch every 3 or four seconds in a video correct? can this be minimized by frame rate selection? why do some of us experience this while others don't?
2015-5-20
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dundee
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Flight distance : 33550 ft

Thailand
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PeteGould Posted at 2015-5-20 00:22
There are several issues you can encounter when working with this kind of footage.  In some ways it ...

I learned something here. Thanks to Golden Pete
2015-5-20
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JakeLikesStuff
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United States
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So... I did my first flight today and didn't pre-edit using QuickTime. I can already see improved results.

Question though...

Exporting, or 'sharing', to a master file, what's the best video codec setting? I went with "Source" which was selected at Apple ProRes 422 Proxy. As you've mentioned above, I know the Inspire isn't recording in that codec. I presume this is what FCP renders it to when I input the files in to FCP, so is that my best option to go with then?
2015-5-20
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JakeLikesStuff
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United States
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So, here’s my first edit of footage without doing a quick edit using QuickTime. Better. Though this is also the first time I shot in something other than 1080p. Maybe I changed too many variables. Regardless I’m happy with the results.

http://youtu.be/C0EwvU2JDCA

Apologies for the music being repetitively annoying. I was mainly focusing on how the visuals were turning out based on my new workflow and shooting at a higher resolution. It was also a difficult fly day so I was really just treating this video as a test.

This was also my first time flying in some extreme wind. It was maybe a little too intense. Ate up almost all my battery life fighting the wind.

Anyhow, all the suggestions above have been greatly appreciated. Thanks everyone.
2015-5-20
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PeteGould
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Dangair Posted at 2015-5-21 11:11
Pete, what you described I'm assuming is the rhythmic pulsing stitch every 3 or four seconds in a vi ...

The hardest work for a video compression engine is in capturing fine detail.  So an aerial shot of mountains in the distance with a lot of puffy clouds over them is easier for the compressor than a low overflight of a pine forest where every pine needle stands out in sharp contrast.  The problem will be further exaggerated with the sharpness cranked up.  And yes, depending on exactly how DJI has the compression set, it is likely that higher frame rates may allow for less data per frame.

As to some people noticing and others not - in many cases it may depend on where they are shooting and therefore what kind of material they're ending up with, as in the example above.  But there is also a subjective issue.  Many people watching video do not notice this artifact unless someone sits with them and points it out.  If you watch satellite or cable TV critically you can find the same thing, because video gets compressed in order to stream it.  It's not very noticeable if the original video is very clean (which a network's video, of course, is).  It can be really bad if you start with video that already has this problem, and then add it again.
2015-5-21
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Michael Starley
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Yes Pete.    Great info!  Thanx!!!      Very good read
2015-5-21
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