My serve. 100 + MPH with video and radar

[Andres]

I recorded a video some time ago, and I just realized I never uploaded it. Sorry about the crappy quality: The cam wasn't that good, and the angle was even worse.

http://www.youtube.com/watch?v=fJPEKZtpOHM

I used maverick1's formula, but tried to make it even more accurate. Instead of counting the frames, I analized the time elapsed between the contact point and the bounce with an audio editor.

It's really simple: You locate both peaks in the the audiowave, and check the time between 'em. After you got that number, you divide it with your camera's fps (mine was 24 fps) and voilà! You have the exact ammount of frames it took to travel from the racquet to the ground.

In the second serve, according to maverick1's formula, the serve was hit at 117/118 mph.

You guys should try this way. I think it's more accurate than simply counting the frames.

[drakulie]

^^That serve is sick. Thanks for sharing that Andres. Much better than the "chair" serve you first loaded a while back.

[Andres]

Shhhh. That chair serve is a classic

[Mike Cottrill]

Originally Posted by Andres Guazzelli

II used maverick1's formula, but tried to make it even more accurate. Instead of counting the frames, I analized the time elapsed between the contact point and the bounce with an audio editor.

It's really simple: You locate both peaks in the the audiowave, and check the time between 'em. After you got that number, you divide it with your camera's fps (mine was 24 fps) and voilà! You have the exact ammount of frames it took to travel from the racquet to the ground.


.

I tried this software and actually not impressed with it. I sure would not pay 150 US for it. The sound graph appears to be sampled at .032 seconds but the frame rate is 29.97 fps which does not line up?? (confused). I tried to use my videos but for some reason it will not read the codec I used even though they are avi files. So, I loaded up Drake’s .mov video that shows a 101 radar reading. If I use the sound spike as the start time and use what appears to be the court contact from the video (no contact sound spike), I get 13.4 frames. Just using the video I guessimated 13.5 frames (btw the software locks at one frame for two frames (two right arrow pushes) but the time scale moves??). If I use the distance traveled to 58.5’ (just a guess since I can not see were he is standing on the baseline??) I get 104.78 mph If I use 59’ I get 105.82mph. If this software is not really off by a frame, add a frame and sub about 5mph.

[J011yroger]

Originally Posted by Mike Cottrill

I tried this software and actually not impressed with it. I sure would not pay 150 US for it. The sound graph appears to be sampled at .032 seconds but the frame rate is 29.97 fps which does not line up?? (confused). I tried to use my videos but for some reason it will not read the codec I used even though they are avi files. So, I loaded up Drake’s .mov video that shows a 101 radar reading. If I use the sound spike as the start time and use what appears to be the court contact from the video (no contact sound spike), I get 13.4 frames. Just using the video I guessimated 13.5 frames (btw the software locks at one frame for two frames (two right arrow pushes) but the time scale moves??). If I use the distance traveled to 58.5’ (just a guess since I can not see were he is standing on the baseline??) I get 104.78 mph If I use 59’ I get 105.82mph. If this software is not really off by a frame, add a frame and sub about 5mph.

That seems reasonable, 101 at the net, 105-106 avg velocity via frame count, and one would guess around 111 off the racquet face as would be measured by pro radar.

J

[Anton]

Originally Posted by Andres Guazzelli

I recorded a video some time ago, and I just realized I never uploaded it. Sorry about the crappy quality: The cam wasn't that good, and the angle was even worse.

http://www.youtube.com/watch?v=fJPEKZtpOHM

I used maverick1's formula, but tried to make it even more accurate. Instead of counting the frames, I analized the time elapsed between the contact point and the bounce with an audio editor.

It's really simple: You locate both peaks in the the audiowave, and check the time between 'em. After you got that number, you divide it with your camera's fps (mine was 24 fps) and voilà! You have the exact ammount of frames it took to travel from the racquet to the ground.

In the second serve, according to maverick1's formula, the serve was hit at 117/118 mph.

You guys should try this way. I think it's more accurate than simply counting the frames.

Light travels almost instantly, sound travels at 335 meters per second, so if you go by sound you have to add (~.05?) seconds to the time as the racket impact sound will be slightly more delayed then the landing sound.

FPS method should be more accurate.

BTW niice serve

[Andres]

No, it wouldn't, because I'm not comparing the image with the sound. I'm comparing the sound with another part of the same sound.
If there's a delay between the actual hit, and the hit audio peak, it's the same delay between the actual bounce, and the bounce audio peak. Therefore, there is no delay in this method.

Plus, I AM using FPS to calculate it. Just doing it more accurately. Instead of using 10 frames or 11, I have a way to measure 10.381 fps, impossible to do by SIGHT.

[Anton]

Originally Posted by Andres Guazzelli

No, it wouldn't, because I'm not comparing the image with the sound.
I'm comparing the sound with another part of the same sound. There is no delay in this case.

Not the same sound, the point of impact is about 15 meters further away from the mic then the point of landing that should make for about .05 second difference,

[Mike Cottrill]

Originally Posted by J011yroger

That seems reasonable, 101 at the net, 105-106 avg velocity via frame count, and one would guess around 111 off the racquet face as would be measured by pro radar.

Actually the speed cal give Vo=Vpeak=Vmax. It provides the maximum velocity not an average. There is significant possible error with the distance and frame count provided to the formula. It appears the radar and the formula is close in readings in this case.

Originally Posted by Anton

Not the same sound, the point of impact is about 15 meters further away from the mic then the point of landing that should make for about .05 second difference,

This is correct. There will be a Doppler effect. With this formula if you want a get a very accurate reading a high frame rate camera should be used along with measuring the distance on court with a string between the contact zones. I would actually like to do this experiment with high speed video and compare the readings to an ATP radar setup. Would be interesting to see the results.

[WBF]

Nice looking serve Andres. Please tell me that wasn't a second serve

[Djokovicfan4life]

Drakulie's serve is definitely over 100 MPH. Look where the ball hits the fence, almost at half the height!

And to those of you who say yours is faster, it may just LOOK faster to you because you are hitting it.

[Andres]

Originally Posted by WBF

Nice looking serve Andres. Please tell me that wasn't a second serve

Of course! that's my regular 120 mph kickserve

What? Like you've never seen one before!! LOL

Hahaha, jk