Simulcasting

The earliest simulcasts date to the 1940s when radio networks began transmitting the same audio over AM and FM to improve reception quality. In 1948, the American Broadcasting Company (ABC) simulcast its television programs on radio for audiences without TV sets.² During the 1950s and 1960s, simulcasting became a tool for stereo broadcasting: FM stations paired with AM to deliver left and right audio channels, a technique later adopted for television's MTS stereo system.

Today, simulcasting is ubiquitous in digital media. Sports networks simulcast games on cable and streaming platforms, and radio stations stream their over-the-air signals online. In 2020, the Tokyo Olympics were simulcast in 4K and 8K on NHK, showcasing high-resolution broadcasts. Simulcasting also enables accessibility: audio description and sign language interpretation can be delivered on secondary channels.

Simulcasting requires synchronization to avoid audio-video lag, often using timecode or network time protocols. Regulatory bodies like the FCC have historically mandated simulcast rules, such as the requirement that FM stations simulcast AM programming during certain hours to preserve local service.³ In the digital era, simulcasting raises copyright issues, as broadcasters must secure rights for multiple platforms.

Simulcasting has niche applications: in the 1970s, some radio stations simulcast with local TV to create "radio with pictures" for concerts. In Japan, "daburu" (double) simulcasts of anime on TV and streaming have become a marketing strategy. Also, emergency alert systems use simulcasting to reach all media simultaneously, and some religious broadcasters simulcast on shortwave and satellite to cover remote areas.

MTS

Multichannel Television Sound, a standard for stereo audio in analog TV.

Timecode

A sequence of numeric codes generated at regular intervals to synchronize audio and video.