Topic: Possible Video Synchronization Improvements
Often videos are compared for a defined movement where the video playback speeds need to be adjusted for a more direct comparison either by reasons of: (1) video capture speeds that are unknown and different than playback speeds for one or both videos or (2) due to the compared movements being executed at slightly different speeds in real time.
An example would be comparing baseball swings of a professional baseball player with an amateur player. Say I am interested in comparing swings from load foot strike to ball contact on the bat. The professional swing might simply be faster and all video capture and playback speeds are known but I want a direct comparison of that movement so I need to adjust playback speeds on one or both of the videos. Or I might have a video of a professional player doing the movement (slow motion or full speed) at an unknown and different capture speed to that video’s playback speed and I need to adjust the playback speed on one of the videos to properly compare the movement.
Videos should be able to be synchronized on a particular frame with videos having different video capture and video speeds (specified or adjusted with Configure Video Timing…) and/or adjusted playback speeds on playback windows and have the same behavior when played using the common (synchronized) controls. This is currently not the case with the current versions of the software. Once playback speeds are adjusted to individually different values, the video that has finished first restarts and keeps playing a number of times and then pauses on the first frame until the other video has finished. Also if you pause and restart the video synchronization, the video that will be the first to finish jumps back a number of frames for some unknown reason before restarting.
- Video that needs to start first begins playing.
- Other video starts at calculated start time to match synchronization point.
- Video that ends first stops on last frame until other video ends at last frame
- Both videos reset to first frame once other video ends at last frame
- Video sequence is restarted if loop function is enabled or if play button activated
Adjustments to the individual video capture and video framerates or playback framerates using the speed control should not affect these principles.
Video 1: 500 frames@60 fps playback speed with speed setting at 1.00X, actual playback speed is 60fps, duration 8.33s
Video 2: 300 frames@30 fps playback speed with speed setting at 1.50X, actual playback speed is 45fps, duration 6.67s
Video 1: Synchronized on frame 180, time 3.000s
Video 2: Synchronized on frame 90, time 2.000s
Calculations determine that Video 1 must start first. The delay in starting Video 2 = 3.000-2.000=1.000s. Video 1 will have played 60 frames before the start of Video 2. Video 2 will be at the last frame before Video 1 is finished at 7.67s (1.000s delay+6.67s duration) and should display the last video frame until Video 1 is ended and reset by the user or loop function. Video 1 will be at frame 460 (7.67s x 60fps) when Video 1 is completed.