1 Physics 160 Biomechanics Instructions for Kinovea Lab 4 Evaluating novice performance versus expert performance Instructor: Dr. Julie Alexander Introduction: In order to objectively analyze a novice performer it is important that the observer understands the key phases of the performance as demonstrated by an expert. In this lab you will compare a novice performance to your previously analyzed expert performance. Purpose: The purpose of this lab is to identify the key phases of your novice performance and then compare body positions of the novice and expert in each of these phases. Kinovea’s many video analysis features will allow you to identify errors or poor technique in your novice performance. You will then discuss how these errors may be corrected to improve performance. Procedure: 1. Load your expert video into Kinovea. Play it to see if it saved the key images and whether or not it saved just the working zone or the whole video. If you saved it before resetting the working zone to the whole video then it would have just saved the working zone. If you chose to save the key images with the video any drawings you did on the key images will appear in the video but the key images won’t appear as small icons below the video unless you saved it as an .mkv. In order to edit key images or delete them altogether you have to do a separate File‐Save and choose Save only the key images data. These images are saved as a .kva (kinovea video analysis) file and will be loaded with the video only if you give this file the same name as the video. If you name it something else you can always load it by clicking on File – Load key images data. The reason you may want this file separate is that you can email it to a friend and they could then load the key images that you worked on as long as they have the original video. (I found all this out the hard way, having lost lots of key images I wanted to edit or save a jpgs!) 2. You may have to redefine your working zone for the expert and resave key images for the essential phases of your expert performance. Make sure everyone in your group is working on the same video and has the same working zone. Each person in the group will analyze different phases of the performance. If your performance had 6 phases then each member of the group should choose 2 phases. Refer to your list from last lab for the phases of the performance and decide among yourselves who is doing each phase. 3. From now on when I refer to the video I am referring to just the working zone. 4. Move to the beginning of your phase in the expert performance and make the first frame of that phase a key image that has a big text box that identifies the phase number and its description. For example “Phase 2: Backswing”. Choose a persistence for this text box that lasts as long as 2 5.
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the phase lasts. Right click on the textbox and choose Persistance, then choose the correct number of frames that shows this phase. Also click on the top left corner of the key image and replace the time with the same title. This will give the key image a name below its icon. Choose a body position in this phase that you think would be a good position to compare to the novice’s body position. You can sharpen up the image by clicking on Image at the top of the screen then choosing Auto Levels or Auto contrast. This may or may not help but try it out. Beware that if you apply an auto contrast you can’t get rid of it later so choose carefully. You can zoom into the body by clicking on the CTRL key and then rolling the mouse wheel in and out. This zoom will allow you to draw on the frame with better visibility. The zoom will not be saved when you save the video. Change the persistence of all future drawings by clicking on Options – Preferences – Drawings – Persistance and then check the Enable persistence box and slide it to 1. Now any drawings you do will stay on one frame and disappear in the next frame. Make a stick figure that represents the body position on this frame using the line tool. Don’t put forces on this diagram. Watch this video on youtube https://www.youtube.com/watch?v=x‐
rEYRqrtxs to see how to make a stick figure. Note that by definition a free body diagram is a diagram that shows only external forces acting on the body; you are not making a free body diagram in this step, you are just making a stick figure. If you want your lines to be yellow for the whole figure then click on the Color Profile icon on the toolbar and choose a thick yellow line that doesn’t have arrows. You can also set how you want the text to appear in text boxes using this menu so that you don’t have to edit each individual text box from now on. Put a text box on this frame that identifies the body position and phase, for example “Expert Backswing, arms at highest position”. Save this frame as a key image and give it a title. Also save this frame as a jpg by clicking on the bottom right icon that says Save Image. You will be able to overlay this stick figure onto the novice video later. Repeat for another body position in this phase. Then repeat for another phase. In total you should analyze at least 3 body positions whether they are in different phases or not. Each member of the group should have 3 different body positions for a total of 9 per group. Save the key image data by choosing Save only the key images data. Name the file with your name, expert and phase. For example “Julie expert backswing and drive.kva” Try the feature that allows you to pause the video at each key image. Click on the bottom right icon that says Save the video with a pause on each key image. Give the video a different unique name that lets you know it has pauses so it doesn’t get confused with the original video. Also save the key image data as a separate .kva file that has the same name so you can edit it later if necessary. Close this video and then reopen to view it with pauses. I think this is a good option for doing a presentation. It allows you to talk while the video is paused. Close it again and reopen the original expert video. Now load the novice video in a second screen. Click on View – Two Playback Screens then click in the dark screen and open the novice video. Watch the novice video and choose a working zone that is as close to the working zone of the expert as possible. Make sure everyone in the group is using the same working zone so that you 3 16.
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can share key image data later. (It is not trivial to load multiple key image data onto one video. I had to do some coding but I’ll look into this more carefully later and let you know how). If you want to see a mirror image of the novice so it is in the same orientation as the expert click on Image – Mirror. Now make stick figures for the same 3 body positions of the novice that you did for the expert and be sure to save the frames as key images and as jpgs. Close the key image viewing bar by clicking on the little arrow on the top right of the pane. See what happens if you use the common controls below both screens to run both the novice and expert videos at the same time. Are they synchronized? You can slow one down by using the sliding button beside speed. Play around for a while to see if you can get both videos to be synchronized. You can use the synchronization button on the common player below the two videos. Move to a similar place in both videos and then click the synchronization button, then play them. Make sure you write down all the settings (speed) and which frame to start them together in so that you can repeat the synchronization without spending more time. You may want to redefine the working zones so they are better synchronized from the beginning. When you have them synchronized call me so I can look at it. You can combine the two videos into one video by clicking on the bottom right icon that says Save both videos into a composite video. You can also save two images as jpgs by clicking the icon on the bottom right that says Save both images to a composite image. You may want to do this with the frames that have the stick figures on them. To do another type of comparison try overlaying a stick figure from the expert onto the novice. Open up the key image windows again for both videos. Click on a key image for the expert then up in the video window right click and choose Send image to the other video. This will put the key image on top of the novice. You can change the transparency of the image by right clicking on the image and choosing Opacity. Change it to about 50% so you can see through the expert to the novice. Alternately you can overlay a jpg image that you have saved by clicking on Image – Observational reference – Import Image. See if you can line up the expert on top of the novice so you can compare their body positions. You may need to use zoom or resize the image. Save the overlay of images as a jpg. Open the key image window again for each video and pause both videos at the same body position. Write a paragraph about each of your 3 sets of body positions comparing the novice and expert. This description would be what a coach might tell an athlete about what she is doing right and what she is doing wrong during her performance. Identify the errors made by the novice performer; briefly describe how these errors negatively impact the outcome. You should also give some suggestions about how to correct the errors. Save all videos, key image data and jpgs to your flash drive. You’ll need them later. Show me your three paragraphs before you leave the lab. You will have to hand in these paragraphs when you do your group presentation so make sure you save them.