***** Why do you see those boom microphones on old TV shows on #YouTube? *****
I'm sometimes asked why when you watch episodes of older TV shows on YouTube, you often see the boom microphones flitting around over the actors at the top of frame, for example, in Johnny Carson's "Tonight Show" and various others. Were the productions really that sloppy?
No, they were not. Analog televisions had considerable "overscan" to hide the "vertical blanking interval" when the cathode ray tube beam or beams would whip back to the upper left of an image to start drawing the next (interlaced, two scans per full image) frame, meaning a considerable number of "lines" of the picture were never seen on conventional TVs, especially at the top. So these shows were shot with that in mind.
When these shows are encoded to digital, if care isn't taken to crop the transcoding in the same manner as the original, those "invisible" lines showing the top of an image that previously could not be seen may become visible. Similarly, other artifacts of the "invisible" lines, including flickering closed captioning data ("line 21") and other data may appear for the same reason.
A similar but different problem can occur in films when boom microphones and other stage equipment become visible in some transfers, but this typically is due to aspect ratio and related theatrical projection "masking" issues, which I will discuss at another time. -L
@lauren the cable network we used to have in Richmond, Virginia appeared to run metadata about the show that was on on the vertical lines off the bottom of the screen.
You could just make them out when you powered off our television. Because the image would shrink to the center and fade as power went out to the tube.
