Getting the Most Out of Your Video

[onehandbh]

drakulie,
Actually I like your motion better. It's more efficient. I'm trying to incorporate
more shoulder turn, coil, a higher toss, smoother uncoiling -- a lot of the things
your serve already has. btw, great recommendation on TT (for the "sonic serve" video).
Just got it today. It really breaks it down into simple steps.

My eventual goal is to be able consistently hit about 120 w/good placement and disguise.
Not sure if it's possible or even realistic since I don't practice serves a lot and I always
have some topspin on my serves. but if I can generate more racquet head speed then
my kick & slice will have a lot more action as well.

btw, did you notice that adding lead increased your
serve power? I've never added lead to my PS 85's b/c I was
afraid it would be harder to hit reaction volleys with in
doubles.

[maverick1]

Originally Posted by drakulie

So how do you conclude 12.5 frames for him and 13 for mine. Even if I am little closer to contact on frame 1.

Sorry for the confusion mav, but this makes no sense.

Drakulie,

I think we are very close to agreeing.

As I mentioned in both my posts, the deduction of 0.5 frames was too high and it should probably be 0.1 or 0.2 frames.

As you say yourself, you are a bit closer to contact(racket looks past vertical) than he is(looks not vertical yet). The deduction for you should probably be 0.1 frames or less.

Looks like your confusion would be resolved if we say your framecount was 12.9 and 1hbh's 12.8. At this minute level, obviously I don't really know. I am pulling numbers out of my ***** If someone else thinks they should be 12.75 and 12.7, I can't argue with that.

Sorry it took so long to clear up. For a while, I wasn't sure whether your issue was deduction of the extra frame at the beginning of the sequence or the 0.5 frames for not yet having made contact in the next frame.

[drakulie]

Originally Posted by maverick1

Drakulie,

I think we are very close to agreeing.

As I mentioned in both my posts, the deduction of 0.5 frames was too high and it should probably be 0.1 or 0.2 frames.

As you say yourself, you are a bit closer to contact(racket looks past vertical) than he is(looks not vertical yet). The deduction for you should probably be 0.1 frames or less.

Looks like your confusion would be resolved if we say your framecount was 12.9 and 1hbh's 12.8. At this minute level, obviously I don't really know. I am pulling numbers out of my ***** If someone else thinks they should be 12.75 and 12.7, I can't argue with that.

Sorry it took so long to clear up. For a while, I wasn't sure whether your issue was deduction of the extra frame at the beginning of the sequence or the 0.5 frames for not yet having made contact in the next frame.

Hey Mav, hope all is well. My confusion is more in part with the accuracy of the formula. Even If I was to plug in "12.9" frames to my serve, the speed would be 109.924 MPH, which is still very high compared to the radar. (+8.9 mph difference).

The way we had originally calculated my serve speed, there was only a difference of 2-3 mph between the calculator and the radar.

This is a big spike in serve speed.

Also, I know my radar is very accurate and calibrated. I have taken it and compared it to those professional baseball radar guns, and the difference is
minus -1 to 2 mph. A lot of times it displays the same speed.

[Mike Cottrill]

Originally Posted by drakulie

Also, I know my radar is very accurate and calibrated. I have taken it and compared it to those professional baseball radar guns, and the difference is
minus -1 to 2 mph. A lot of times it displays the same speed.

The formula is good. It is the “d” and the fps that must be input that draw differences. The small differences in frame count make the difference. The frame count becomes more clear with the 240 fps thus the more accurate a calculation.

[maverick1]

Originally Posted by drakulie

Hey Mav, hope all is well. My confusion is more in part with the accuracy of the formula. Even If I was to plug in "12.9" frames to my serve, the speed would be 109.924 MPH, which is still very high compared to the radar. (+8.9 mph difference).

The way we had originally calculated my serve speed, there was only a difference of 2-3 mph between the calculator and the radar.

This is a big spike in serve speed.

Also, I know my radar is very accurate and calibrated. I have taken it and compared it to those professional baseball radar guns, and the difference is
minus -1 to 2 mph. A lot of times it displays the same speed.

Even if the radar is perfect, it can only measuere the speed when it "sees" the ball. The ball slows down by at least 3 mph in the first 5 feet.
I once suggested to you a simple experiment to test the range of your radar - place it on the other side of a fence and hit some simple forehands at the fence. Vary the distance between the fence and the radar until you find the maximum distance at which it shows the ball speed. That is the range of your radar.
Once you know the range, we will be in a much better position to discuss the accuracy of the formula.

The other thing is you may be overestimating the distance you plug into the formula. You could have struck the ball deeper inside the court than you thought, or the ball could have landed more than a few inches short of the line. People underestimate distance from the line when looking at the bounce from the other side of the court. When I feel like I just missed a shot long, I sometimes ask by how much it missed, and I am invariably shocked when they 1 foot or even 2 feet. Other times, I think the ball was on the line but they will tell me it was well in.

[drakulie]

Originally Posted by maverick1

Even if the radar is perfect, it can only measuere the speed when it "sees" the ball. The ball slows down by at least 3 mph in the first 5 feet.
I once suggested to you a simple experiment to test the range of your radar - place it on the other side of a fence and hit some simple forehands at the fence. Vary the distance between the fence and the radar until you find the maximum distance at which it shows the ball speed. That is the range of your radar.
Once you know the range, we will be in a much better position to discuss the accuracy of the formula.

yeah, I haven't done that yet, but will give it a go next time I get the chance, and follow up with you.

Originally Posted by maverick1

The other thing is you may be overestimating the distance you plug into the formula. You could have struck the ball deeper inside the court than you thought, or the ball could have landed more than a few inches short of the line. People underestimate distance from the line when looking at the bounce from the other side of the court. When I feel like I just missed a shot long, I sometimes ask by how much it missed, and I am invariably shocked when they 1 foot or even 2 feet. Other times, I think the ball was on the line but they will tell me it was well in.

The spot where the ball landed left a mark so the distance is accurate. In fact, the day I took the video, I kept serving over and over until I got a serve as close to 100 mph, and right on the cross of the T. That is why I used this particular serve. It was 101, and right on the T.

Again, when we first did the calculation, the formula and the way we were using it calculated my serve speed at around 103+ MPH (+2 to 3 mph), from the radar speed of 101.

Now it is calculating it at 109-111 MPH (+8-10 mph faster) than the radar.

No way this is accurate. Maybe it is not the formula that is innacurate, but the way we are using the formula.

If I stay at 13.5 frames I am much closer to the radar's 101, than if I go to 12.5 frames, 12.9 frames, or 13 frames.

[maverick1]

Originally Posted by drakulie

If I stay at 13.5 frames I am much closer to the radar's 101, than if I go to 12.5 frames, 12.9 frames, or 13 frames.

The one thing I am sure about is the number frames. It is 12.9 or 12.95 or something like that.

If the formula is wrong, it is wrong. So far I have no reason to believe that. But it is not for me to pronounce it correct. I have posted all the details of the formula on the website along with my email address, but I have not had any comments on its vailidity.

We will have to wait for you to do the range test now. If you come back and say the range is 25 feet, that would explain an 8 mph difference. You have seen yourself that the speed registered drops rapidly as you move the radar further away from you.

You may think that you have it placed it just the perfect distance because moving it any closer doesn't increase the speed resgitered. However, as you move it closer, a different reason for understating speeds kicks in - the angle beween the line of the ball's movement and the radar's line of sight to the ball becomes larger and larger. For example, if you place the radar 9 feet from the baseline, and make contact at a height of 9 feet, the radar will show a speed that is 70% of the actual speed.

Having a technical background, I am all too aware of the two above mentioned deficiencies of low end radars. This is why I haven't yet got it even though I am curious about speeds and the price is less than that of a racket.

[maverick1]

http://fcchandler.home.comcast.net/stable/index.html

This is a free video editing software that seems to be able to play most formats of video, though it doesn't have the frills of commercial software.
Most importantly, you can use arrow keys to step a frame at a time.

It doesn't have an installer. You have to unzip the files into folder.
It is convenient to create a shortcut on your desktop for the main program, VirtualDub.exe

[Mike Cottrill]

Mav,
Nice little program for free. Better than wind DVD from what I have seen so far. It appears to show 240 fps as 120 fps and video is clearer. It must be the interlacing thing. Cyber Link still shows frames a little better IMO but video is less sharp. Virtual Dub program counts 53 frames and Cyber link shows 106. Another video in normal mode shows 30 frames with cyber link and ~15 or 16 with Virtual Dub. Odd thing with Wind DVD is appears the ball lands out but it is clearly in with the other two programs. Counting the frames accurately is downfall with 30 fps video.
Odd thing, as I remember I did get a little more on the slow mo serve, but it did not seem like that much more. The serves are just about identical.
Nice program.

[onehandbh]

maverick1,

I believe you made an error in calculating the number of
frames in drakulie's video. Go back and replay the
serve video and you will find that there is actually one
more entire frame that is before the first frame in the
jpeg sequence of drakulie's serve that will show the
actual contact point. The ball has already traveled about
a foot at the point of the first frame in the montage of
serve sequences posted earlier that was used to count
the number of frames in his serve video. The
ball just happens to be in front of the racquet from the
angle of the camera and that's why it *appeared* to be the
contact point but is not.

If we assume that the total distance traveled by the ball
is: 60 feet - 6 inches (distance inside service line) and
drakulie contacted with the ball at 1 foot inside the service
line (since drakulie said he landed 1 -2 feet inside the line)
then we get 58.5 feet as the distance.

Then plugging 13.9 frames into the calculator, we get...

** 101.008780 mph **

... which is stunningly close to what the radar recorded.
Very well done creating the formula!

Originally Posted by maverick1

The one thing I am sure about is the number frames. It is 12.9 or 12.95 or something like that.

If the formula is wrong, it is wrong. So far I have no reason to believe that. But it is not for me to pronounce it correct. I have posted all the details of the formula on the website along with my email address, but I have not had any comments on its vailidity.

We will have to wait for you to do the range test now. If you come back and say the range is 25 feet, that would explain an 8 mph difference. You have seen yourself that the speed registered drops rapidly as you move the radar further away from you.

You may think that you have it placed it just the perfect distance because moving it any closer doesn't increase the speed resgitered. However, as you move it closer, a different reason for understating speeds kicks in - the angle beween the line of the ball's movement and the radar's line of sight to the ball becomes larger and larger. For example, if you place the radar 9 feet from the baseline, and make contact at a height of 9 feet, the radar will show a speed that is 70% of the actual speed.

Having a technical background, I am all too aware of the two above mentioned deficiencies of low end radars. This is why I haven't yet got it even though I am curious about speeds and the price is less than that of a racket.

[drakulie]

Originally Posted by onehandbh

maverick1,

I believe you made an error in calculating the number of
frames in drakulie's video. Go back and replay the
serve video and you will find that there is actually one
more entire frame that is before the first frame in the
jpeg sequence of drakulie's serve that will show the
actual contact point. The ball has already traveled about
a foot at the point of the first frame in the montage of
serve sequences posted earlier that was used to count
the number of frames in his serve video. The
ball just happens to be in front of the racquet from the
angle of the camera and that's why it *appeared* to be the
contact point but is not.

This is completley incorrect.

The "16 frame action shot" is a frame by frame (one after the other) captured from the video to the software that comes with the camera. Contrary to what you state, in the 1st frame in the "16 frame action shot", the ball has still not been struck.

The software inside the actual camera allows you to view frame-by-frame, while the entire video is still saved in the camera. The frame before the first frame I posted, in the "16 frame action shot", clearly shows the racquet head is not close to contacting the ball, and has not yet reached a completely vertical position, therefore I did not bother including it. So there is no way the ball has been struck on the frame before.

In addition, 3 things do not support what you are stating:

1. The camera was not placed directly behind me, rather behind me and to my right on the fence. I am serving from the left side of the center hash mark, and the direction of the serve is going to the right (AD Side). In other words it is traveling into the "sites" of the camera, not away. So if it has already travled a foot,,,,,,, because of the position of the camera and direction the ball is traveling you would clearly see the ball without any obstruction from the strings.

Your scenario would only apply if the camera were directly behind me and/or more to the left of me for this to be possible.

2. If I already struck the ball, and it traveled a foot, my hand, arm, and racquet face would already be pronating downwards, with the racquet face side that hit the ball going to the right (like in your frame numbered "2"), which they are clearly not in the first frame. However they are in the second frame.

3. This radar does not pick up the ball immediately at contact, rather as the ball approaches an area in front of the radar. So we know for a fact the speed at contact is faster than the speed shown on the radar. In other words, for the video I recorded at 101 mph, the actual speed is 2-3 mph faster at contact. 103-104 mph, at minimum.

For your calculations to apply, it would mean the radar speed would have shown 97-99 mph, and the calculator would show 101.

[drakulie]

Originally Posted by maverick1

Even if the radar is perfect, it can only measuere the speed when it "sees" the ball. The ball slows down by at least 3 mph in the first 5 feet.
I once suggested to you a simple experiment to test the range of your radar - place it on the other side of a fence and hit some simple forehands at the fence. Vary the distance between the fence and the radar until you find the maximum distance at which it shows the ball speed. That is the range of your radar.
Once you know the range, we will be in a much better position to discuss the accuracy of the formula.

Hey Mav. I did the "fence test", LOL.

The radar begins to have problems picking up speeds outside of the 18' mark. So, when it gets with in the 18' foot range it starts reading the mph.

[onehandbh]

drakulie,
First, Here is a description of the frames in the picture:
FRAMES p1 to p4 are 4 consecutive framesof the toss as it is going up to
show the path of the ball.
FRAMES -2, -1, 0, 1, 2, 3, 4 are consecutive frames leading up to the
moment of impact and after it. Frame 0 is closest to where contact
occurs.

I'll provide a short gist of the analysis followed by a more detailed one
below to fully explain my analysis. I think what happened is that your
camera gave you 16 frames but what happened is that from the
small LCD display it looked like the contact point but actually it
wasn't. I would have thought it was too, until I was able to see the
previous frames in detail using the elecard software, which can
capture all video frames individually in sequence.

I apologize if it comes across abrasive or anything. I was just trying to
find out why there was just a discrepancy between the radar and formula.

Here's is the short explanation of how I know there is one more frame.
Looking at the sequence of frames:

- The toss moves the ball from right of the picture to left, as is consistent with pros' tosses. Moving in a parabolic motion from right to left.
- In this case the ball has clearly moved to the right from one frame to the next, so the ball must have been struck to cause it to move back toward
the right.

---- warning: long detailed analysis below ----------------

Frame:
(p1 - p4):
We see that the ball is traveling upward on the right side of the little
tree. It appears to go up in a more or less straight path.

(p4):
Here we see taht the ball exited on the ride side ofthe little tree.

(-2):
The has not droppe back into view of the camera yet. It will come in at
about the peak of the little tree.

(-1):
If you look carefully, you will see that the ball has just begun to enter
the frame where I have drawn a red arrow.

(0):
The has continued to drop into frame and the racquet has either made
contact or is about to make contactd. Just like the ascent, it is traveling
in a more or less straight path down. It is, however, slight to the
left of where it exited the frame on its way up. This tells me the toss
traveled it a parabola going right to left.

(1):
The ball has already been struck. How do I know? Because it is now A
LITTLE TO THE RIGHT of it's previous location in frame (0). This cannot
be due to the toss because the toss has a slight RIGHT to LEFT
path. Therefore, the ball must have been struck. The serve is going
toward the ad court so this makes sense. Why does the racquet appear
to be in front of the ball? Because the camera is slightly to the right
of the center line and drakulie has begun his pronation going left to
right. Just by coincidence of the location of the serve and camera, for a
brief moment the racquet is still in front of the ball. This is probably why
you thought that was the contact point.

Also, the racquet angle with respect to the court of the frame in which I strike
the ball is very similar to the frame 0 in the picture above. If your serve has
a lot of topspin then it is unlikely that the angle would facing so much more
down toward the ground than my serve, which has topspin but is not my
heavy kick serve.

[maverick1]

FWIW,
I think onehandbh made a good observation wathing the ball relative to the tree in the background. It proves that contact has already happened in the frame that we previously thought was just prior to contact. So we are talking total frame count over 13 rather than below 13.

[drakulie]

Onehand, don't worry as I did not take your post as abrasive in any way. As I said, I am as anxious as you to ensure the formula is accurate.

Your above post is a very good one, very good sound observation, and as you said, I would be unable to see this detail on the small LCD screen. My apologies!

Unfortunately, taking your observation-- then it is clear proof the formula is innacurate.

As I pointed out in my previous post, "point #3" ---With your observation and calculations you got ** 101.008780 mph ** using the formula. The radar showed 101 mph. There is no way, for the radar and the formula to coincide so decisively. If my serve is 101.008780 using the formula the radar would have to show a much lower recorded speed.

Remember, the ball has already slowed down significantly when it has entered
the radars path in which it picks up the ball speed. Therefore, if the formula were accurate, then the radar would have displayed a speed much less than 101.

The radar was placed for this serve approximately 30 feet from the baseline. Based on the test I did today, the radar did not pick up any serve speeds 18 feet away. It began consitently picking up speeds inside and including the the 15 ft range, although it did pick up a couple from 16, and 17 feet, but not as consistently as 15 feet. So, in my serve the ball travled at least 15 feet (almost to the service line) before the radar calculated the speed (see frame # 7 of my original action shot when the radar light shows a display for the first time).

Maverick has previously pointed out, the ball loses about 3 mph in the first 5 feet. So the radar would have shown at minimum a speed 98 mph not 101. In my case, the ball traveled an additional 10 feet, in which there would be even more decreas in speed than 98 mph.

So one of two things is possible:

1. The formula is innacurate, and actually calculates a slower speed than actual speed at contact---or;

2. Pilor error-- The number of frames that are suppose to be counted and entered into the formula is innacurate.

[maverick1]

1hbh used 13.9 frames in his calculation.

I don't agree that 0.9 frames have passed after contact. I just calculated that, in 0.9 frames, a 100mph ball should travel 4.4 feet. It clearly hasn't traveled that far. Because of the angle, It is very difficult for me to say if the ball has traveled 1 foot or 2 feet in this frame. If it is 1 foot, you should be using 13.2 frames, which gives a speed of 106.37 mph with 58.5 feet of distance.

That gives you a reasonable 5.37 mph for the speed by which the ball slowed down beore the Radar picked it up.

[drakulie]

Originally Posted by maverick1

I just calculated that, in 0.9 frames, a 100mph ball should travel 4.4 feet. It clearly hasn't traveled that far.

I think we could all agree on this.

Originally Posted by maverick1

Because of the angle, It is very difficult for me to say if the ball has traveled 1 foot or 2 feet in this frame. If it is 1 foot, you should be using 13.2 frames, which gives a speed of 106.37 mph with 58.5 feet of distance. That gives you a reasonable 5.37 mph for the speed by which the ball slowed down beore the Radar picked it up.

Actually, in this scenario, the ball traveled an additional minimum of 11-13 feet before the radar picked up the speed of the ball, in which there is more loss of speed, that are still unnacounted for.

Mav, hope you haven't lost your mind yet. LOL

[onehandbh]

LOL. hey maverick1, just to make things even more complicated for you,
some more things to take into consideration:

- condition of the balls and type of balls. (how fuzzy and old are they?)
- Which brand? (e.g. new dunlop balls seem to be very fast relative to some
of the other brands).
- Also humidity and temperature of the outside air
and balls.
- elevation? (e.g. serves at mile high would be faster)

drakulie, can your radar work if it points at the serve from the side?
so that you can get the moment right after contact w/the racquet?
Is that how the pro serves are measured?

The angles of the serves in our videos are best for viewing but unfortunately
it's hard when to see when the moment of impact is. It may be that the formula
will always have a limiting factor due to the quality of the footage and our
ability to figure accurately approximate the moments of impacts.

P.S. drakulie, you should show those two frames to ball control tennis &
tell him/them/it that you mastered the prolonged contact serve where
you can keep the ball on the racquet for 2 feet, so there 4 ms
contact is nothing.

Originally Posted by drakulie

Actually, in this scenario, the ball traveled an additional minimum of 11-13 feet before the radar picked up the speed of the ball, in which there is more loss of speed, that are still unnacounted for.

Mav, hope you haven't lost your mind yet. LOL

[maverick1]

Originally Posted by drakulie

Actually, in this scenario, the ball traveled an additional minimum of 11-13 feet before the radar picked up the speed of the ball, in which there is more loss of speed, that are still unnacounted for.

Mav, hope you haven't lost your mind yet. LOL

It is definitely possible to tweak the estimated numbers to get exact agreement.

First, if the Radar detected the ball after about 11 feet, I would expect a slow down of about 6 mph. (If the slowdown is 3 mph in the first 5 feet, the next 5 feet would see a smaller decrease).

The distance traveled in that frame could be 6 inches rather than 1 foot, in which case the frame count would be 13.1 and not 13.2
The total distance might have been 58.9 instead of 58.5. That gives 108 mph
The Radar may well have rounded 100.5 to 101. That gives a difference between radar and formula of 7.5 mph.

So we now have *too much* of difference - we expected 6 mph difference but have 7.5 mph.

I hope you are now getting the drift. The entire error can be explained by an error in estimated inputs, without needing to question the formula itself. Of course, this doesn't PROVE that the formula is right. All I am saying is there is no reason to doubt the formula; there has never been in my mind throughout this thread.

Of course, you can question the usefulness of the formula if it is possible to get a 5mph difference by estimating the frames/distance slightly differently. But the Radar is also liable to give very different readings depending on how far away and at what angle it is placed.

To answer 1hbh's points about the effects type of ball, humidity etc., No model of a real world phenomenon can take into account every variable that might have an effect on the phenomenon. The best you can hope for is that you have considered the most important variables and the effect of the rest can be ignored.
It is true of every gadget you take for granted. The odometer in your car is counting the number of revolutions of a wheel and muliplying that by some constant to get distance traveled. The actual distance would be affected by wear in the tire, air pressure in the tire and other variables.

[drakulie]

Yeah Mav. That is why I say, it could very well possibly be pilot error when inputing the # of frames and distance into the calculator.

You have been such a good sport, and very helpful. Do you work for Nasa?

Anyways, this ones for you,;:

For he's a jolly good fellow, For he's a jolly good fellow,For he's a jolly good felloooooow.....

Which nobody can deny!