Merging video and data

Rocket electronics have gotten quite cheap - small altimeters and decent HD cameras can be had for as little as $30, putting "instrumented rocket flight" within the reach of every rocketeer. Most folks are content with keeping the video and data separate, but I have always been intrigued with synchronizing the data with the video, so that each frame can be tied to a specific height, speed, acceleration, etc. My first experiments (back in 2017) in doing this involved my Windows PC laptop and a program called DashWare; the software was somewhat cumbersome from a usability perspective (hey, it was free!) and so I soon lost motivation. Too much work!

DashWare created video

Time passes and new software appears. Late last year, I discovered that there was this software application called RaceRender, with capabilities like those offered in DashWare. The good news was that it was available for MacOS, meaning I could make use of my big screen iMac in creating data-synced videos; the bad news was that it cost money, especially if you wanted to remove the stupid program logo/watermark from the videos. After a bit of research, I made the plunge and bought the software. Fortunately, I was not disappointed with this purchase (unlike some others in the past).

Regardless of whether you use DashWare or RaceRender, you need two things to create a data-synced video - the video from the camera and the data from the altimeter, flight computer, or whatever. The video must be in a format readable by the software - not a problem for the cameras generally used by rocketeers - and the data should be in a file with numbers arranged in a comma separated value format (csv). Files downloaded from all logging altimeters of which I am aware are in this format, so again no problem. You may have to edit the csv file to remove parts before launch and well after landing, but this is pretty easy using Excel or some other spreadsheet application. The only gotcha is understanding the limitations of the software - for example, RaceRender can't deal with negative speeds, so you need to take the absolute value of speeds from altimeters (e.g., FlightSketch Mini) that give the descent speeds as negative.

RaceRender screen capture (Click to enlarge).

Once you have the input files properly formatted, you import them into the software and select the ways you want the data displayed - simple numbers, gauges, or graphs; it's up to you. Then you have to sync the data to the video by selecting a video frame corresponding to the first line of data, usually t = 0, the time of first motion on the launch pad. This is easy to do with most rocket videos, as first motion is readily apparent when you step frame by frame through the movie (unless the camera is pointing up - then it is really hard). You then invoke application's sync feature, et voila! The data is now properly displayed on the video as it plays. The final step is exporting your project into a standalone video, which you can share with your buddies on YouTube, FaceBook, etc.

This past Sunday I flew my Estes Solo with an Estes Astrocam and a FlightSketch Mini, as I wanted to get some footage of the glider separating from the rocket near apogee. The flight was successful - the C6-3 motor carried the rocket up to 222 feet and the glider separated at 200 feet, on the way down. I would like a better camera than the Astrocam - the shutter can't handle fast motion (distorts) and it does not have a good depth of focus - but better cameras are heavier and not easily carried by low impulse model rockets. I eagerly look forward to such critters appearing on the market.

Frames from the data-synced Solo video (Click to enlarge).