On-screen display

An on-screen display (abbreviated OSD) is an image superimposed on a screen picture, commonly used by modern television sets, VCRs, and DVD players to display information such as volume, channel, and time.

In the past, most adjustments on TV sets were performed with analog controls such as potentiometers and switches. This is still used in modern monochrome portable TVs. After remote controls were invented, digital adjustments became common. They needed an external display, which was LED, LCD, or VFD based. Including this display increased manufacturing costs.

When electronics became more advanced, it became clear that adding some extra devices for an OSD was cheaper than adding a second display device. TV screens had become much bigger and could display much more information than a small second display. OSDs display graphical information superimposed over the picture, which is done by synchronizing the reading from OSD video memory with the TV signal.

Some of the first OSD-equipped televisions were introduced by RCA in the late 1970s, simply displaying the channel number and the time of day at the bottom of the screen. An OSD chip was added to the General instruments (GI) varactor tuning chip set designed in conjunction with RCA and Telefunken. The original OSD was merely to placate users who were faced with a snowy screen during auto tuning. Something the original architecture had not seen as an issue until it was first demonstrated. Once a display had been injected it was simple, in the next iteration, to add a real time clock (RTC) to display time and date. In the 1980s, OSD-capable TVs started to be more common, such as Zenith's "System 3" series. Akai have been credited with the introduction of OSD in VCRs in the 1980s, including the introduction of on screen programming. By the mid-1990s, VCRs with these displays became widely available. This made it possible to reduce the size (and cost) of the VFD or LCD in the VCR. Eventually, as VCRs declined in popularity and prices fell, many manufacturers dropped the internal display completely, relying completely on the on-screen display. All DVD players also use on-screen displays. Many PAL television sets use the internal Teletext decoder's graphics rendering system to further reduce costs.

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