Terrence Raymond Smith

The US HDTV standard

This standard for digital high-definition television has been submitted to the Federal Communications Commission for its approval. Based as it is on the MPEG-2 video compression and transport protocol, multiple transmission formats, Dolby AC-3 digital audio, and vestigial sideband digital modulation, this HDTV system will supply the home with superb images and spectacular sound while also, as part of the National Information Infrastructure (NII), relaying digital data. An HDTV system employing multiple transmission formats, digital compression, packetization, and modulation techniques is a marked advance over current world television standards such as NTSC, PAL, or SECAM. >

Encoding for Compatibility and Recoverability in the ACTV System

This paper describes an advanced compatible television (ACTV) system intended for the single-channel transmission of widescreen EDTV images. Existing NTSC receivers display a selected 4: 3 portion of the widescreen image with standard NTSC resolution. However, a new widescreen receiver, tuned to the same 6-MHz RF channel, displays a widescreen image with a resolution in excess of 400 lines/picture height in both spatial dimensions. To produce the NTSC-compatible signal, the original widescreen high-definition signal is separated into four components: (1) the main NTSC signal with the side panel low frequencies time compressed into the horizontal overscan regions, (2) the time-expanded side panel high frequencies, (3) the extended horizontal-luminance detail, and (4) the extended vertical-temporal luminance detail. Components 2 and 3 are quadrature modulated at low amplitude by a new phase-controlled subcarrier at 3.1 MHz. Component 4 is inserted in quadrature with the RF picture carrier. This paper discusses how the four components are processed to insure full compatibility at the NTSC receiver and complete recoverability at the ACTV receiver.

Decoding issues in the ACTV system

The advanced compatible television (ACTV) system is a proposal for the single-channel transmission of widescreen enhanced-definition television (EDTV) images. A widescreen high-definition source is encoded into a signal that is NTSC-compatible. Existing NTSC receivers display a selected 4:3 portion of the widescreen image with standard NTSC resolution. A new widescreen receiver is proposed, tuned to the same 6 MHz RF channel, that displays a widescreen image with a resolution in excess of 400 lines/picture height in both spatial dimensions. The encoding process is reviewed and the recovery of various signal components to produce the widescreen image in the ACTV receiver is discussed. >