1seg is a mobile terrestrial digital audio/video and data broadcasting service in Japan, अर्जेन्टिना, ब्राजील, चिली, uruguay, पाराग्वे, पेरु, and the Philippines.

1 seg is designed as a component of ISDB-टी, the terrestrial digital broadcast system used in those countries, as each channel is divided into 13 खण्डहरू, with a further segment separating it from the next channel; an HDTV broadcast signal occupies 12 खण्डहरू, leaving the remaining (13th) segment for mobile receivers, त्यसैले नाम, “1seg” वा “एक Seg”. See full seg.