1seg is a mobile terrestrial digital audio/video and data broadcasting service in Japan, আর্জিণ্টিনা, ব্রাজিল, চিলি, উরুগুয়ে, প্যারাগুয়ে, পেরু, 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 বিভাগগুলি, with a further segment separating it from the next channel; an HDTV broadcast signal occupies 12 বিভাগগুলি, leaving the remaining (13th) segment for mobile receivers, hence the name, “1seg” অথবা “এক seg”. See full seg.