Digital television systems
Most current digital television systems are based on the MPEG-transport stream standard, and use the H.262/MPEG-2 Part 2 video codec. They differ significantly in the details of how the transport stream is converted into a broadcast signal, in the video format prior to encoding (or alternately, after decoding), and in the audio format. This has not prevented the creation of an international standard that includes both major systems, even though they are incompatible in almost every respect.
ATSC and DVB
The two principal digital broadcasting systems are ATSC, developed by the Advaned Television Systems Committee and adopted as a standard in the US and Canada, and DVB-T, the Digital Video Broadcast – Terrestrial system used in most of the rest of the world. DVB-T was designed for format compatibility with existing direct broadcast satelitte services in Europe. There is also a DVB-C version for cable television. While the ATSC standard also includes support for satellite and cable television systems, operators of those systems have chosen other technologies (principally DVB-S or proprietary systems for satellite and 256QAM replacing VSB for cable). Japan uses a third system, closely related to DVB-T, called ISDB-T, which is compatible with Brasil's SBTVD. In China they developed and use a fourth system, named DTMB.
