Yulia Lipnitskaya | Page 198 | Golden Skate

Yulia Lipnitskaya

Yamita

Yamita

On the Ice
Joined
Oct 19, 2014
Vanshilar said:
Oops. Apparently I missed the last few pages of this thread. :slink:

Anyway, I use Matlab the way somebody uses Microsoft Excel. It's a really really big program geared more for academia or engineering, but one of its features is that it has an easy user interface for doing C-like programming (without having to worry about all the variable declarations, etc.). So depending on what I'm doing, I'll use either Matlab or Excel.

Anyway, for the jumps, there's nothing really mystical about it. Assuming we can ignore things like air friction and how extended the skater's legs are during takeoff, there's an easy relationship between the jump's height and how long the jump is in the air. The rest comes down to details, like how the person actually counts the number of frames. For me, I look at the first frame when the skater is in the air at the beginning of the jump and the first frame when the skater touches the ground at the end of the jump. This is because video capture is discrete; the actual time of takeoff is between the last frame when the skater is still on the ground and the first frame when the skater is in the air, and the same thing for the landing. Thus counting the number of frames in this way more closely approximates the actual time.

......
Click to expand...
Vanshilar. Thank you for the explanation. I appreciate your scientific approach. :yes:

I know it is difficult to use only publicly available videos but did you try to measure how fast skaters spin? Conceptually, a low jump with fast spin can have the same quality of a high jump with slow spin. It seems that a ratio between spin speed and jump speed (or something similar) would be a good measure of jump quality. Well ..., that is, if those high quality data are available. :scowl:

I also understand your discussion on time measurement (number of frames), the margin of error is large if one uses 25 or 30 fps videos. Where/how do you get higher FPS videos? I am very curious. :think:

I am actually working on a project (using your approach) to see how Lipnitskaya's jumps evolve from EC2014, Olympics, WC2014, to recent GP competitions. I did not observe any obvious changes of her jump heights so far. I will post more if I find anything interesting.
 
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Alba

Alba

Record Breaker
Joined
Feb 26, 2014
Vanshilar said:
But yeah, that's why I collect as many different videos as much as possible, to find which once I can do the most accurate analysis for different aspects. Hmm maybe I should make a separate thread about it. I was going to put jump height analysis along with my analysis of jump rotation (i.e. amount of pre-rotation and landing underrotation) but that's going to take a long time. Looking at jump height is much easier to do if people would be interested in it.
Click to expand...

Thank you so much, Vanishilar.
I suppose that's a huge job, but I think people would be very interested in this.
How do you recognize higher FPS videos? Is there something we can do to help find them?
 
V

Vanshilar

On the Ice
Joined
Feb 24, 2014
Alba said:
Thank you so much, Vanishilar.
I suppose that's a huge job, but I think people would be very interested in this.
How do you recognize higher FPS videos? Is there something we can do to help find them?
Click to expand...

Usually what I do is to download the videos (either it can directly be downloaded from the site, or if it's something like Youtube then I use clipconverter.cc which is a website that will let you download Youtube and other videos without hassles like installing a downloader etc.; note that it also tells you the video details such as resolution). Then I can right-click on the file, select "Properties", and then click on the "Details" tab, which will give basic information about the video such as resolution and FPS. I can also open the file in Avidemux (which I will need to in order to do any processing anyway) and click on the "info" button. This needs to be used carefully however. The video still needs to be examined for repeated frames. Sometimes people will take (for example) 25 FPS video and increase it to 30 FPS video simply by inserted repeated frames after every 5th frame. Such videos actually should still count as 25 FPS.

When the video is watched on higher resolutions, sometimes you will see horizontal lines ("combing"), especially at the left and right borders of moving objects. This is an artifact of interlacing. A good example is the 4th copy of Tuktamysheva's GPF FS here: https://www.youtube.com/watch?v=WKLUOkENBsE around 40 seconds in when she is moving across the camera's field of view (watch it on 720p or 1080p). Interlacing ( http://en.wikipedia.org/wiki/Interlaced_video ) was used on older TVs that displayed the odd lines of an image (as the scanner was moving down), and then the even lines of the image (as the scanner moved back up), to make the perceived motion smoother. For my purposes, what it really means is that each image actually contains two separate images taken at two separate times, effectively doubling the frame rate. So an interlaced video at 25 FPS is really 50 FPS once de-interlaced. I can extract the separate frames via Avidemux's "interlace->separate fields" filter and thus look at them separately.

So basically, the biggest thing to look for is the horizontal lines with moving objects, because that will mean I can double the effective FPS for more accurate jump height measurements. The other things to look for are the video's FPS, as well as resolution (higher is better for both).
 
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Isabel_O'Reilly

Isabel_O'Reilly

Final Flight
Joined
Nov 30, 2013
Vanshilar said:
Usually what I do is to download the videos (either it can directly be downloaded from the site, or if it's something like Youtube then I use clipconverter.cc which is a website that will let you download Youtube and other videos without hassles like installing a downloader etc.; note that it also tells you the video details such as resolution). Then I can right-click on the file, select "Properties", and then click on the "Details" tab, which will give basic information about the video such as resolution and FPS. I can also open the file in Avidemux (which I will need to in order to do any processing anyway) and click on the "info" button. This needs to be used carefully however. The video still needs to be examined for repeated frames. Sometimes people will take (for example) 25 FPS video and increase it to 30 FPS video simply by inserted repeated frames after every 5th frame. Such videos actually should still count as 25 FPS.

When the video is watched on higher resolutions, sometimes you will see horizontal lines ("combing"), especially at the left and right borders of moving objects. This is an artifact of interlacing. A good example is the 4th copy of Tuktamysheva's GPF FS here: https://www.youtube.com/watch?v=WKLUOkENBsE around 40 seconds in when she is moving across the camera's field of view (watch it on 720p or 1080p). Interlacing ( http://en.wikipedia.org/wiki/Interlaced_video ) was used on older TVs that displayed the odd lines of an image (as the scanner was moving down), and then the even lines of the image (as the scanner moved back up), to make the perceived motion smoother. For my purposes, what it really means is that each image actually contains two separate images taken at two separate times, effectively doubling the frame rate. So an interlaced video at 25 FPS is really 50 FPS once de-interlaced. I can extract the separate frames via Avidemux's "interlace->separate fields" filter and thus look at them separately.

So basically, the biggest thing to look for is the horizontal lines with moving objects, because that will mean I can double the effective FPS for more accurate jump height measurements. The other things to look for are the video's FPS, as well as resolution (higher is better for both).
Click to expand...

Is this video what you mean? When viewed in 1080p there are horizontal lines on the screen which disappear when I downloaded it. On Realplayer.
 
Meoima

Meoima

Match Penalty
Joined
Feb 13, 2014
Sam-Skwantch

Sam-Skwantch

“I solemnly swear I’m up to no good”
Record Breaker
Joined
Dec 29, 2013
Country
United-States
Meoima said:
She has become a beautiful and elegant lady!! :drama: so mature
Click to expand...

I know right. She is definitely growing up so fast. It feels like yesterday when someone first showed me her 2012 JWC FS :love:

Just for fun here is a throw back to 2011.

http://youtu.be/5DlQqRP6jZ4

For ironic purposes at 1:40 I definitely spotted Nina Mozer. :laugh:
 
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Yamita

Yamita

On the Ice
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Oct 19, 2014
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