domenica 8 maggio 2016

MH17: video artifacts in Zuhres BUK video

Update: I was informed by some reader that there exist a 1080p version of the Zuhres video, so I repeated the analysis below to that version of the video. Here's the result:
Indeed, the artifacts are much smaller in this version. However, they are still there, and again they apply only to the cabin of the truck, and not to the rest of the convoy.

Last night I happened to stumble again on the video of the BUK being towed by a track in Zuhres, and I noticed some video artifacts as the truck moves behind the building: on the white wall, you can see parts of the truck. I loaded the video file in Blender, and watched the magnified video in slow motion, and indeed those artifacts were there. So, I've prepared a demonstrative video which shows the effect more in detail, and uploaded it to Youtube:

I'm not an expert in digital video analysis, but I don't recall having seen any similar artifacts in other videos. You can see some artifacts on the image right before the truck disappears behind the building (at 00:06-00:07 of my video), and these might be the result of the video compression algorithm; however, at 00:09-00:10 you can actually see parts of the truck cabin being drawn on the building's wall. In my experience, digital video compression sometimes causes residual parts of a previous video frame to be shown over the current frame, when the movie is heavily compressed. However, in this case what we see is a completely new image: none of the previous video frames show the truck's cabin in that position. Also, the video is moderately compressed and of pretty good quality overall; and last, given that the building's wall is uniformly grey and square-shaped, it would seem weird that the compressor has decided to put some image elements in it, and made the image more complex: usually, compression algorithms simplify the video frames.
But, as I said, I'm not an expert on this matters. If you are, or know someone who is, please ask him to have a look at this video, and share his opinion, along with his CV, blog or linked-in profile (just to be sure that we are actually talking with some authoritative expert, and not just another wannabe expert like me :-) ). Also, examples of similar artifacts in other raw videos are very welcome.

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3 Commenti:

Anonymous Lena ha detto...

The truck cabin is mostly white. Shot a 1080p video youself with an iPhone with the same distances between camera, a light grey building and truck with a white cabin at about midday when no shadows (cloudy). There are no shadows on the Zuhres video. What seems like a shadow from the mast, isn't. Look at shorter poles: no shadows. Satellite photo of that place when not cloudy:

8 maggio 2016 14:56  
Anonymous Lena ha detto...

Looks like the compression artifacts are mostly of the software you are using for magnification. Make screenshots in .png format with , enlarge them without interpolation with : Image - Scale image - Interpolation:None, specify size in exactly 2 or 4 times larger.

8 maggio 2016 16:14  
Blogger Alberto Mardegan ha detto...

Lena, it was sunny, almost midday and shadows are rather short. You can see the shadow from the shorter pole here: (the photo with the APC)

By the way, what would be interesting to know is, why don't we see the APC in this video?

8 maggio 2016 23:32  

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