Timecode skips frames 0 and 1 of the first second of every minute, unless….To achieve this, SMPTE created an algorithm which works as follows The objective of drop-frame-timecode is to align the frame count with time of day on the station wall clock so that playout schedules and edit systems continue to operate without error. It’s important to remember, that there are no video frames dropped or lost but instead the count of frames is adjusted to correct the ambiguity between the wall clock and frame-count time. To fix the timing difference, the Society of Motion Picture and Television Engineers (SMPTE) developed a system called drop-frame-timecode. This would be completely unacceptable as Ad-breaks would be crashed and revenue lost. However, using 30/1.001 fps means we loose 1.5 minutes per day from our programming schedule. It’s common for broadcasters to use frame-count as their reference for program and edit timing. However, as the frame rate is running at 30/1.001 fps, the number of frames per hour played from the server is 60 secs x 60 mins x 30/1.001 fps = 107,892.1079 frames, a loss of 107.8921 frames, just under 3.5 seconds an hour, or 1.5 minutes a day. To put this into perspective, if the USA system used 30fps then there would be 108,000 frames in 60 minutes, that is 60 secs x 60 mins x 30 fps. If this was left unadjusted, the time on the video playout server or tape player would be running slower than the wall clock by approximately 0.1% as there are less frames in an hour at 30/1.001 fps than at 30fps. The figure 29.97 is the rounded off equivalent of 30/1.001 as described in the article – NTSC Line and Frame Relationships. The first time of the day is 00:00:00:00 for both USA and European systems, and the last time of the day is 23:59:59:24 for European systems and 23:59:59:29 for USA systems.įor systems using the USA’s 59.94 fields per second, or 29.97 frames per second, counting time is much more complex. And minutes start at 00 and run through to 59. The hours use the 24-hour clock and start at 00 for midnight all the way through to 23 for the hour just before midnight. Frame counts start at 00 and end at 24 for the European 25 frames per second and start at 00 and end at 29 for USA 29.97 frames per second.
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