All HD networks use Dolby Digital AC3, many with 5.1, others with 2.0. Even those with 5.1 capability still have many 2.0 programs.
All HD networks distribute their HD format of choice in the native resolution, which is either 1280x720p or 1980x1080i, except for a few premium movie channels which reduce horizontal resolution to 1440x1080i. This is generally not much of an issue because of the film based programming.
HD networks are distributed in both MPEG2 and MPEG4. Neither is technically better for image quality, but MPEG4 is a more efficient video codec and when used is less expensive to distribute HD via satellite.
All over-the-air broadcasts are MPEG2, even though some OTA networks like ABC & NBC distribute to local affiliates in MPEG4.
A forum community dedicated to home theater owners and enthusiasts. Come join the discussion about home audio/video, TVs, projectors, screens, receivers, speakers, projects, DIY’s, product reviews, accessories, classifieds, and more!