
What causes the green line in the frame before the puck hits the camera? - sillysaurus2
http://www.gifexploder.com/exploderesults.aspx?fn=puck.gif
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djent
The way I see it happening is that the video is delayed enough so that when
the puck actually hits the camera, the video gets encoded[insert correct
technical term] wrong - green - for that line. Then we actually get the video
of the puck hitting the camera.

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oakwhiz
So... the physical impact against the camera is causing a fault with the video
encoder on the camera?

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drakaal
More likely caused the sensor to send invalid values for pixels.

Still More likely the jostle caused data loss for a while.

The green squares don't look to be 16 pixels tall. Hard to tell with the
footage, but DC's are typically 16x16 or 8x8

This looks to be a CCD issue not a compression issue especially since the
artifacts don't propagate to the next frame, nor cause variations in the
sharpness of things in the next frame which would be common if new image data
had to be created in whole rather than as a differential from the perfectly
noiseless, "broken" frame before.

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bobdvb
Can I suggest that the loss of signal during the impact caused an issue with
the encoder but because of the encoding of video if the disrupted frame was an
i-frame or a b-frame then it might cause effects on p-frames?

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drakaal
There are two impacts. In front of the glass is a light mesh that is used to
keep water from kicked up is from showing as droplets on the screen. That mesh
is coated in a hydrophobic material and works well keeping a camera from
needing to have the lens wiped.

The Green Line is when the camera took that part of the impact. Likely the
Sensor shook enough to cause an error.

It recovered in the frame before the puck hit the lens so there is a clear
frame before that.

The comments about IPB frames and compression might seem logical at first, but
B frames are very rarely used in live broadcast because they add so much to
the delay, and cause a lot of issues when broadcast over lossy formats.

If this was a broadcast from tape, the impact could have damaged the tape when
the tenisioner was jostled by the impact, but typically that would do more
than the small ammount of frame loss shown here, and wouldn't have been part
of a live broadcast.

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ricardobeat
In the frame where the glitch happens the puck still looks quite far from the
lens. If the mesh was positioned that far it would probably be visible and
mess up autofocus.

B frames or buffering would only add <100ms latency, while live transmission
already has at least 1s lag, before even considering 'tape delay'. I'm betting
on processing delay as the explanation.

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drakaal
The mesh is about 3 feet out.

B Frames to be of any use require 6 frames at 33ms each, that is 200ms, a
quarter of a second, but on play back you need all of the frames in the set
from i frame to i frame to get make the reference frames work, this is
typically 1-3 seconds.

-Brandon Wirtz SMPTE Voting Committee Member for the ratification of H.264 and VC-1 standards.

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DrRandell
Could be any number of things. If the camera is analog then sync is carried on
the "green" channel. That's why most video imperfections are green. I would
need more information on the camera and camera system

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mertd
My guess is that those particular scanlines were being read out at the
instance of the impact, which momentarily flexed the circuitry and caused
funny things.

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Luc
Could the green line correspond to the moment the camera was hit, and the next
'closer' image show the rebounding of the puck?

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graeham
Looking at image No. 28 (after green line), the image is considerably darker
and more pixelated than No. 26 and previous. The green line could be artifact
from an auto-contrast or auto-focus.

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kineticfocus
It seems to be a problem with raw sensor information prior to encoding,
otherwise I figure there would be more blocky image corruption.

Frame 0-26: Puck Flying

Frame 27: Impact g force shorts capacitor (usually rated for ~10g), scanline
loses chroma until circuit at proper threshold again.

Frame 28: Frame dims b/c of occlusion from puck, and collision likely turns
glass into a negative meniscus lens.

Frame 29->: Officially an inelastic collision. Time to get a new camera

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larrys
To add to rampant speculation without enough details my theory would be that
it's some kind of a light reflection artifact off the puck corresponding at
the exact moment of the camera scan lines and frequency.

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ubersoldat2k7
The camera shit its pants!

