Timing issues with media players

Tech Note: TN0981
Product: RV2, OpenEx, Synapse
Version: All
Date Added: 2016-08-22


Media players do not provide synchronized playback for viewing or scoring recorded data. Because media players use time rather than frame number, playback will inherently lag behind data playback and this lag becomes longer over time. This happens because the frames per second (FPS) value is always rounded to an integer while the TDT clock runs at 24414.0625 Hz. If you select an RZ sample rate of 30 Hz, the actual sample rate is the corresponding fixed or realizable sample rate. For example: A rate of 24414.0625 / 30fps = 813.8 samples per frame. This gets rounded to 814. When stimulation is triggered at 24414.0625 / 814 = 29.9927 fps, which is the real FPS that the RV2 is triggered at and the video is stored at. When viewing in a media player that thinks the video is recorded at exactly 30fps, the time difference after 1 minute is [(30 / 29.9927) * 60000 ms/min] - 60000 = 14.6 ms


Use the Video Viewer in OpenScope for synchronized data scoring.