What is the ATSC standard?

It is intended to replace the NTSC system used mostly in North America and produces wide screen 16:9 images up to 1920×1080 pixels in size — more than six times the display resolution of the earlier standard. However, a host of different image sizes are supported, so up to six standard-definition "virtual channels" can be broadcast on a single TV station using the existing 6MHz channel. ATSC also boasts "theater quality" audio because it uses the Dolby Digital AC-3 format to provide 5.1-channel surround sound. Numerous auxiliary datacasting services can also be provided.