Getting the Most Out of Your Video

Hi everyone,
Just wanted to make a post to let people know that I'm writing a series of articles on improving your tennis video skills, whether you are filming yourself, or filming someone else. It's going to be a multipart series, and my goal was to explain things in very plain english.

Part 1 is online now, and it focuses on understanding frame rates and interlacing, and how those two things affect your tennis video.

http://www.fuzzyyellowballs.com/getting_the_most.php

Hope everyone enjoys,

Adam Sieminski
 

onehandbh

G.O.A.T.
I've done this before, but there is huge human error involved. If you look at the results, one tenth of a second difference = huge:
.5 = 106mpm, .4=133mph, and of course one tenth of a second would be pretty good degree of accuracy for most humans.

Better Solution, use an oscilloscope with a microphone attached that is rigged to actually start and stop a timer on the spikes. ie on the contact of the serve and contact against a piece of plywood placed at the baseline.

Another way to implement your idea would be to just get a cassette
recorder and let it record. Then import the file video to your
computer via some free sound editing software like audacity. You
can then see the spikes of where the ball was struck and when it
hit the court.
 

matchpoints

Professional
I like the ideas of using Audio over video. On video one would have to look at the ball leaving the racquet and also the bounce. This could be somewhat subjective and also most people do not have access to high speed cameras. With audio the sound spikes are clear as day. I have a software on my Treo 700p called CallRec that easily records and transfers audio to my pc and I can use it from just standing on the sideline between the server and service box. I'll give it a go and see how well it works. Thanks for the ideas guys. With my laptop on site It should be a relatively quick process as audio files are way smaller then video.

Stopwatch? we're not timing runners, we're timing a fast ball and have to hit the button twice....accurately.
 
Last edited:

5263

G.O.A.T.
Hate to blow this whole math exercise, but did anyone take into account that the ball slow by about 51% from the contact of the serve, to the contact of the return?
For the Pros, the radar setup picks up in the first 2-5 feet for those big numbers we all read about. You guys seem to be figuring out and avg speed for 60 feet???
 

hyogen

Hall of Fame
Looking for consumer Camcorder for sports? Sony DCR-DVD505 Smooth Slow Recording 240fps

Looking for a consumer Camcorder for sports? As of 10-3-2006, Sony has a selection of camcorders that can record short clips at 240fps. Great for analyzing strokes and for calculating serve speeds.
Sony:
“Smooth Slow Recording
By increasing the record rate from 60 fields per second (fps) to 240 fps for 3 seconds allowing you to capture 3 seconds of fast motion and play the video back in 12 seconds. This is great for analyzing a golf swing or a viewing a bird in flight”
At times in normal mode, it appears that the camera playbacks 30 or 60fps. Most likely just an interlacing adjustment the camera does with on board processing.

I personally have this one:
DV55.jpg


3 seconds if enough time to capture the serve motion and the ball reaching the fence if serve is at least in the upper 80’s. Resolution in smooth slow recording mode is far less than in normal mode, but still very useful for analyzing sport strokes. Nice camera for every day recording as well.

Here is a link to the selection of camcorders:
http://www.sonystyle.com/is-bin/INT...mcordershop&ref=http://www.sony.com/index.php


Examples and editing to come soon.


man that camera sounds awesome. 240fps!!! is there something cheaper that can do this? maybe not use DVD to record. digi cam? doesn't have to be 240fps..
 

Mike Cottrill

Hall of Fame
man that camera sounds awesome. 240fps!!! is there something cheaper that can do this? maybe not use DVD to record. digi cam? doesn't have to be 240fps..

They do no longer make the DVD505. If you do not get a model that has the 240fps feature, I would not get a consumer Sony camcorder. Reason: unless they have changed recently, Sony does not provide manual shutter speed control (need high shutter speed to eliminate the motion blur of each video frame or field). Also, models like mine have a max shutter speed of 1/500sec which is not fast enough to stop a tennis ball with out blur. As far as I know, Sony is the only consumer video camcorder that has high frame rate capture.

If you are looking for a cheep camera that has manual shutter speed, folks have had good success with: Canon-ZR series 850. It is less than 300 US dollars now. That is the camera that Hi-Tech Tennis uses.

For reference, see thread: http://tt.tennis-warehouse.com/showthread.php?t=146855&highlight=video+camera

Here is a link to a 240 field per second (120 frame per second) video I took with the Sony DVD505: http://www.hi-techtennis.com/serve/martin_serve_open.php

Mike
 
Last edited:

hyogen

Hall of Fame
incredible. that is an awesome vid of todd martin. Looks VERY Much like pete sampras' serve in my opinion.

maybe I can buy a used dvd505. I will look into this: Canon-ZR series 850

I wonder what camera Fuzzy Yellow Balls .com uses... they have a few really nice quality high speed videos
 

Mike Cottrill

Hall of Fame
I wonder what camera Fuzzy Yellow Balls .com uses... they have a few really nice quality high speed videos

I believe it is from a company called Southern Vision Systems and is from the MemView line of cameras. I would bet is cost about the dollars of a new sub compact car.
 

5263

G.O.A.T.
Brad Gilbert was a counter puncher, not a pusher. JohnnyMac just said that to get his goat.

I think Mac was more of a pusher than Gilbert. He couldn't hit bigger than Gilbert with that conty grip of his. Hahahaha

Just no one calls u a pusher when u are #1 in the world I guess.
:-?
 

hyogen

Hall of Fame
I believe it is from a company called Southern Vision Systems and is from the MemView line of cameras. I would bet is cost about the dollars of a new sub compact car.

how does fuzzy yellow balls make money :eek: people send in videos to be analyzed? i thought their whole site was free
 

5263

G.O.A.T.
So,
has anyone figured in and accounted for the deceleration of the ball by about 50% over the 60 feet?

Is it as easy as adding 1/3 of the avg mph for 60 feet?

The correct mph over 60 feet should be about 3/4 of the correct highest speed at impact, so by adding back the missing 1/4th or 1/3of the avg mph, wouldn't you get the proper mph at contact?

If this isn't correct, it should be pretty darn close, right?
 

5263

G.O.A.T.
what happened to this thread? Was no one accounting for the rapid decel of the ball over the distance to the returner?
 

Mike Cottrill

Hall of Fame
what happened to this thread? Was no one accounting for the rapid decel of the ball over the distance to the returner?

Could you be more specific on what topic and issue you are referring?
If you are talking about the serve calculator, it takes into account the ball from contact with the racquet to contact with the court for the serve. With the main data provided is the Max Velocity of the serve.
 

5263

G.O.A.T.
Several post were talking of counting frames of the ball travel against time, with a known film speed, thus giving an avg mph over the distance, but not the max speed of the ball.

I'm not sure about the serve calculator.
 

5263

G.O.A.T.
Okay.

I get 13 frames: if I don't count the frame at the moment of contact w/racket
and click until it hits the court.(and including that frame where the ball
hits the court) Is that right? According to the calculator (for 30 fps)
the serve would be 111 mph.

If count the frame at the moment of contact then 14 frames would come
out to 103mph.

This is an example of the post I was reading. Does this calculation take into account the rapid decel of the ball during the travel. If it does, it is not obvious to me and adding one more frame to the count would not make the speed change if it did.

right?
 

Mike Cottrill

Hall of Fame
This is an example of the post I was reading. Does this calculation take into account the rapid decel of the ball during the travel. If it does, it is not obvious to me and adding one more frame to the count would not make the speed change if it did.

right?

The serve calculator accounts for the effect of drag on the ball. The reason one frame effects the max velocity of the ball is that another frame increases the time it takes to make contact with the court (this means a slower initial velocity). The serve calculator provides max velocity as well as the average speed from frame contact with the ball to the ball making contact with the court. A derivation of the formula can be found here:
http://tt.tennis-warehouse.com/showpost.php?p=986488&postcount=9

The more frames per second the camera records the more accurate time can be observed. In the example you provided it appears the video was recorded at 30 frames per second and determining the frame (time) the racquet makes contact with the ball and the frame (time) the ball makes contact with the court is not clear. So, the user of the tool interpolated or guessed the number of frames it took to go between the contacts. Also, accurate calculation of the distance the ball travels between string contact and court contact is important.

Here is an example of what the calculator provides:

ServeCalSnapShot.jpg
http://i62.photobucket.com/albums/h104/GreenTennis/ServeCal/ServeCalSnapShot.jpg?t=1210131230

Hope this helps
Mike
 

5263

G.O.A.T.
Yes Mike, that does help greatly, but the numbers on the decel still don't look right to me. where did that 120 down to 87 in 60' come from. I think the 87 is too high.

like in the example, a 110 serve should only be about 60-65 at the bounce opposed to the 90 I think I saw in the example.
 

Mike Cottrill

Hall of Fame
Yes Mike, that does help greatly, but the numbers on the decel still don't look right to me. where did that 120 down to 87 in 60' come from. I think the 87 is too high.

like in the example, a 110 serve should only be about 60-65 at the bounce opposed to the 90 I think I saw in the example.

The number 120 to 87 mph came from research group that John Yandell worked with. The number was calculated from Pete Sampras’ serve.
Here is the link: http://wings.avkids.com/Tennis/Project/speed-02.html
http://wings.avkids.com/Tennis/Project/our_team.html

The 93.62 mph number you reference is the average speed of the ball while in the air before the bounce. The 80.16 mph is the speed at the time of the bounce. The 93.62 is a calculated by the simple formula distance/time.

The drag coefficient for a Tennis ball was calculated from the above listed web site’s research. There may have been an assumption on the distance those serves traveled 60’. I do not recall at the moment. If you have some data that contradicts the assumptions made, please let us know. I did check this formula against a serve from roddick at the AO and it was very close. If you have serve data to compare that would be great. Here is a link to the speed calculator:
http://donthireddy.us/tennis/speed.html
 

5263

G.O.A.T.
Looks like we are using the same source on our info. I must just be making some incorrect assumptions in there somewhere. I remember Yandell stating that a served ball had lost almost exactly 50% of the initial speed by the time it was struck by the returner. Of course, this doesn't give an exact rtn spot or distance in feet, so it is just a good rule of thumb.

Thanks for your help.
 

mntlblok

Hall of Fame
Looks like we are using the same source on our info. I must just be making some incorrect assumptions in there somewhere. I remember Yandell stating that a served ball had lost almost exactly 50% of the initial speed by the time it was struck by the returner. Of course, this doesn't give an exact rtn spot or distance in feet, so it is just a good rule of thumb.

Thanks for your help.

IIRC, the ball loses a significant additional amount of speed between the time it strikes the ground and when it leaves the ground, and also loses additional speed between the time it leaves the ground and when it reaches the baseline. I'm thinking that this would yield the 50% reduction in speed about which you recall.

Kevin
 
Lots of threads have been popping up recently about videos, calculating speeds, and other related topics. I'm going to (for now) sticky a thread where you can post links and other resources for how to get the most out of your video...

Thanks to user Mike Cottrill for suggesting this thread, and the first link of the sticky:

http://tt.tennis-warehouse.com/showthread.php?t=99228http://tt.tennis-warehouse.com/showthread.php?t=121904
"Calculating Serve Speed from a digital Video"

Please help out by adding more links!
I got 404 not found trying these links. Are they no longer good.
 

Chas Tennis

G.O.A.T.
I got 404 not found trying these links. Are they no longer good.
The post that you were reading was 2006. (Click the circle arrow.)

If you want video stroke advice, I have posted a great deal on that.

If I posted on your interest, I might be able to find it. ?

I believe that Wikipedia has a great thread with the top serve speeds of many ATP players.
 
Last edited:

Chas Tennis

G.O.A.T.
The post that you were reading was 2006. (Click the circle arrow.)

If you want video stroke advice, I have posted a great deal on that.

If I posted on your interest, I might be able to find it. ?

I believe that Wikipedia has a great thread with the top serve speeds of many ATP players.
I have posted on measuring serve speed with a video camera. I did it at the US Open and posted it here. 123 MPH or 132 MPH might have been my measurement. I posted it several other times. I don't believe anyone ever tried it and posted about it.

It is the simplest way to measure velocity. Be squarely to the side viewing the trajectory. Get two frames and the use the time between frames on the video camera. 1/30 sec, 1/60 sec etc.

You can use the diameter of the ball to calibrate the distance scale and I gave instructions. But it is better to use a measuring tape along the trajectory.

Here are some search finds
 
Last edited:

Digital Atheist

Hall of Fame
I got 404 not found trying these links. Are they no longer good.
Original serve speed calculator works very well assuming decent footage and a minimum 60fps (30fps requires too much guess work for an accurate reading):

But it has been dead for a long time, so you need the way back machine:

If you want to use it again, just save the entire page as html (web page complete) and then you can run it locally, since it is only client side Javascript performing the calculations.
 
Top