CompuServe Messages

John, >> – The changing of the line frequency solved the problem of interference (audio or video depending on who you read I guess) but caused another problem, what was the problem and how was it solved? -<< He..He.. this answer is well known: Good morning Class…welcome back to Videotape Operations 101. Today we're going to discuss _Color Frame Rate_. We have discussed how we have changed the line frequency of our signal because of the interference we got from the audio and the original color subcarrier. Because of this change, we are now working on a 15,734 lines per second rate. But that slightly slower line frequency produces a frame rate of 29.97 frames per second. So we are no longer working on a thirty frame per second system. Consequently, all of our standards have changed. It used to be very easy to time a television system because you worked on a 60 fields per second rate, and that timed out perfectly with 60 cycle AC current. With color television, that is no longer true. We work at a 29.97 frames or 59.94 fields rate. We no longer lock properly with 60 cycle current. Uh…Mr. Ellis…Is that another MAD Magazine? Pass that up front Mister! Now….to continue: Because of this, all of our timing standards now refer to the subcarrier frequency as the primary synchronization source. We no longer pay as much attention to "H" (horizontal) lock or the "H" (horizontal) synchronization signal, which used to be referenced to 60 cycle current. Everything has now become referenced to the color subcarrier of the television signal. We could get in to "Signal Timing" at this point but I'm gonna give this a pass for now. Note: This change in frame rate is what eventually caused the two systems of time code to come into existence – drop frame and non-drop frame time code. Now….How much do we want to know about time code? Class????? This is fun! <BG> Murph'