Autosyncing 3rd party video with data.
Whilst using video from a 3rd party video recorder and using it along side data in the analysis software is powerful and flexible, there is the significant problem of how to synchronise the data accurately.
To manually synchronise data and video the user selects a point (or 2 points) in the data and video that match, and these points are “locked together”. However, in practice locating suitable points in the data can be quite difficult. Normally the advice is to choose the first braking or acceleration point in the data, but still accurate synchronisation is difficult.
To simplify this process Race Technology sell the optional “video synchroniser” adapter. This is a simple way to synchronise data from a Race Technology data logger and almost any video recording system.
To use the video synchroniser it helps to understand its operation. The unit is simply a special LED that flashes in a fixed sequence when logging data. To use the system:
- The 3rd party video recorder is started
- The data logger is started, this starts the LED flashing
- After the recording is completed
- The data logger is stopped, this stops the LED flashing
- The 3rd party video recorder is stopped
When you load the video into the analysis software, the software scans the video for the flashing LED and locates the exact time when it first starts to flash and when it stops flashing. These times are then used to synchronise the video and data with excellent accuracy, typically just a few frames of video.
To avoid distracting the driver, the LED is a special type that can be seen by the video system, but it is “out of the range” of the human eye. Also to allow the system to work in bright daylight and in dark conditions it “auto dims” itself so it’s never too obtrusive I the video.
Before the video is analysed to find when the LED starts and stops flashing, it locates where in the frame the LED is located automatically. This means that the location of the LED is not important.
Due to the way the system works means that there are a few limitations:
- The video synchroniser must be visible in the video frame the whole time, so it must be located so it cannot be blocked by the driver getting in the way etc.
- The video synchroniser is assumed to be in a fixed position in the video frame for the entire recording, if the video recorder or the video synchroniser move relative to each other automatic synchronising will fail
- The video must include the a few seconds of no data logging (and so no flashing) at the start and end of the recording
If for any reason the automatic synchronisation fails then the analysis software will give a warning message and the data and video will have to be manually synchronised.
A typical installation is shown in the figure below:
In this case the video camera is mounted on the roll cage towards the rear of the car looking forwards, recording both the driver, the car interior and the track. The video synchroniser is mounted either on the dashboard, or at the top of the windscreen. In either case the LED is clear of the driver and in full view of the video recorder.