Getting the Most Out of Your Video

Discussion in 'Tennis Tips/Instruction' started by diredesire, Oct 2, 2006.

  1. adamsieminski

    adamsieminski New User

    Joined:
    Sep 27, 2007
    Messages:
    33
    Location:
    Washington, DC
    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
     
    #51
  2. onehandbh

    onehandbh Hall of Fame

    Joined:
    Dec 19, 2005
    Messages:
    3,072
    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.
     
    #52
  3. chroix

    chroix Rookie

    Joined:
    Jul 5, 2006
    Messages:
    133
    Use a stop watch? Is it 1850? That seems crazy inaccurate to me.
     
    #53
  4. matchpoints

    matchpoints Professional

    Joined:
    Feb 21, 2004
    Messages:
    929
    Location:
    Billings, MT
    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: Mar 19, 2008
    #54
  5. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    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???
     
    #55
  6. hyogen

    hyogen Hall of Fame

    Joined:
    Sep 4, 2007
    Messages:
    2,951
    Location:
    Portland, Oregon

    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..
     
    #56
  7. Mike Cottrill

    Mike Cottrill Hall of Fame

    Joined:
    Sep 3, 2004
    Messages:
    1,626
    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: Apr 2, 2008
    #57
  8. hyogen

    hyogen Hall of Fame

    Joined:
    Sep 4, 2007
    Messages:
    2,951
    Location:
    Portland, Oregon
    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
     
    #58
  9. Mike Cottrill

    Mike Cottrill Hall of Fame

    Joined:
    Sep 3, 2004
    Messages:
    1,626
    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.
     
    #59
  10. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    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.
    :-?
     
    #60
  11. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    sorry, wrong thread. yikes:confused:
     
    #61
  12. hyogen

    hyogen Hall of Fame

    Joined:
    Sep 4, 2007
    Messages:
    2,951
    Location:
    Portland, Oregon
    how does fuzzy yellow balls make money :eek: people send in videos to be analyzed? i thought their whole site was free
     
    #62
  13. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    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?
     
    #63
  14. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    what happened to this thread? Was no one accounting for the rapid decel of the ball over the distance to the returner?
     
    #64
  15. Mike Cottrill

    Mike Cottrill Hall of Fame

    Joined:
    Sep 3, 2004
    Messages:
    1,626
    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.
     
    #65
  16. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    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.
     
    #66
  17. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    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?
     
    #67
  18. Mike Cottrill

    Mike Cottrill Hall of Fame

    Joined:
    Sep 3, 2004
    Messages:
    1,626
    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:

    [​IMG]

    Hope this helps
    Mike
     
    #68
  19. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    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.
     
    #69
  20. Mike Cottrill

    Mike Cottrill Hall of Fame

    Joined:
    Sep 3, 2004
    Messages:
    1,626
    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
     
    #70
  21. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,404
    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.
     
    #71
  22. Mike Cottrill

    Mike Cottrill Hall of Fame

    Joined:
    Sep 3, 2004
    Messages:
    1,626
    #72
  23. mntlblok

    mntlblok Professional

    Joined:
    Jan 15, 2006
    Messages:
    859
    Location:
    Savannah
    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
     
    #73

Share This Page