Oarstack Analysis

Do you ever get to the end of a race and think “I wish I knew the coefficient of variation of our catch timing during that piece,” or “What was the standard deviation of our drive/recovery ratio?” Or even something esoteric like “What was the stroke rate?” Well now you can find out with Oarstack analysis!


One word of caution before we start – it’s not YouTube.  When you click the play button your browser has to download the full 1920×1080 high quality video file, regardless of the resolution you’ve chosen or the speed of your connection.  It’s not ideal if you’re paying by the megabyte.

Things to do

  • You can just use it as a player.  You’re watching the files that get uploaded to YouTube, but without the extra compression that YouTube can add.
  • Change the playback speed by clicking the ‘1x’ button on the bottom right.
  • Everything revolves around markers, which you place at the current time using MARK CATCH and MARK EXTR. buttons on the control bar.  If all you want to do is measure stroke rate then all you need to do is place the catch markers.
  • Clicking on a marker takes you to it, and the MARK button becomes and UNMARK button to remove the marker.
  • The step and frame advance buttons can are handy to step through the video.  There are time buttons, where ‘0.5s’ steps forward half a second, and frame buttons, where ‘-4f’ steps backward four frames.  These buttons can be held to step continuously, and holding ‘1f’ gives a handy slow playback.
  • Once you have a few markers, you can get at the data by either hovering the mouse over the markers themselves or reading the tables below the video.
  • The tables can be cut and pasted into spreadsheets, and then used to make graphs, etc.
  • Right now the only way to store markers is by embedding them in a link using the box below the video.  If you share those links the markers will be there when anybody clicks the link.  You can edit the numbers in the link too.
  • You don’t have to use the markers just for catches and extractions.  With of bit of invention you can measure how well the crew is in time, etc.  Or at least you could if I’d taken it a bit more easy with the zoom lens.
  • Form a crack team of specialists to find out the best time to say the catch has actually happened.  Is it when the blade first touches the water?  Or when when it’s covered?  Or when it’s half way in?  Likewise for extractions, which tend to be more ropey.  In theory there’s an ideal point that gives you the lowest standard deviations, but as far as I know it’s one of the great unknowns of modern science.  It’s right up there with Dark Matter.

On that last one, for now let’s go with the catch having ‘happened’ when the spoons are, averaged over the crew, 50% in the water.

Browser quirks

The analyser is abusing HTML5 and Javascript quite a bit, and is a bit ‘experimental’.  Here are a few of the things that don’t quite work.

  • Internet Explorer: Nothing works at all until the entire video has loaded, including (inconveniently enough) the load progress meter.
  • Opera: Clicking on the video itself only toggles pause/play whilst the button is held – it doesn’t toggle pause/play per press like other browsers.
  • Firefox: Video flickers black momentarily when you use the controls.  ‘1x’ playback speed only goes down to 0.25x.
  • Chrome: Is not bad – nothing to report so far.
  • Safari: This is the only browser that can play video backwards smoothly – keep clicking 1x and you’ll get negative numbers.  Behaves badly until the entire video is loaded.
  • Mobile devices: I haven’t found one that works at all yet, although some will at least play the footage.
  • Browsers without HTML5 support: No support for these, if you can find one.

Feel free to log issues here: https://github.com/sloe/analyseapp/issues or mail to [email protected].