1seg is a mobile terrestrial digital audio/video and data broadcasting service in Japan, Ra-Parata, Beresiria, Tireni, Uruguay, Paraguay, I Peru, and the Philippines.

1 seg is designed as a component of ISDB-T, the terrestrial digital broadcast system used in those countries, as each channel is divided into 13 te mau tuhaa, with a further segment separating it from the next channel; an HDTV broadcast signal occupies 12 te mau tuhaa, leaving the remaining (13i te 10) segment for mobile receivers, hence the name, “1seg” e aore ra, “I te hoe Seg”. See full seg.