Craig Campbell Todd

Compatible digital audio for NTSC television

A method and apparatus for transmitting a digitally modulated Quadrature Phase Keyed (QPSK) audio carrier signal, or a digitally modulated Quadrature Partial Response System (QPRS) audio carrier signal, wherein the audio carrier signal is located 1.2 MHz below the video carrier of an NTSC signal. This places the digital audio signal 300 KHz above the analog FM sound center frequency of the NTSC signal in the adjacent lower channel, 4.8 MHz above the video carrier of the adjacent lower channel NTSC signal and at the edge of the lower vestigal video sideband components of the NTSC signal with which the digital audio signal is associated.

ATSC Video and Audio Coding

In recent decades, digital video and audio coding technologies have helped revolutionize the ways we create, deliver, and consume audiovisual content. This is exemplified by digital television (DTV), which is emerging as a captivating new program and data broadcasting service. This paper provides an overview of the video and audio coding subsystems of the Advanced Television Systems Committee (ATSC) DTV standard. We first review the motivation for data compression in digital broadcasting. The MPEG-2 video and AC-3 audio compression algorithms are described, with emphasis on basic concepts, system features, and coding performance. Next-generation video and audio codecs currently under consideration for advanced services are also presented.

Stereophonic motion picture photographic sound-tracks compatible with different sound projection formats and record and playback apparatus therefore

Discrete four-channel photographic (optical) motion picture sound-tracks are disclosed that are compatible with existing monophonic and stereo variable area (SVA) theatre projection equipment. Six track and four track embodiments are disclosed. In the four track embodiments 4-4-4 matrix encoding is employed in producing the sound-track. Apparatus for recording and reproducing the compatible four-channel sound-tracks are also disclosed.

Aspects of current standardization activities for high-quality, low-rate multi-channel audio coding

This paper analyzes directions in the current standardization activities for multi-channel audio, briefly reviews the composite coding schemes AC-3 and ISO 11172-3 compatible systems, and discusses requirements, features, and time-tables for the audio systems in the ISO/Moving pictures Expert Group (MPEG) phase 2 and the United States high definition television (HDTV) standardization processes.<<ETX>>

A Compatible Digital Audio Format for Broadcast and Cable Television

The addition of a digitally modulated carrier to the M-NTSC broadcast television signal would make it possible for television broadcasters to deliver digital audio and data. In laboratory tests, a QPSK carrier modulated with 512 kbits/sec of data has been added at a frequency of 4.85 MHz above the vision carrier. At a carrier level of -20 dB with respect to vision carrier, the new signal has been shown to be compatible with the BTSC stereo and SAP signals.

Digital Audio Delivery to the Consumer

Dolby Digital is a system for coding up to 5.1 channels of audio into a low bit rate data stream intended to deliver audio to the consumer. High quality is obtained with compression ratios approaching 12:1 for multichannel audio programs. The high-compression ratio is achieved by methods that do not increase decoder memory and, thus, cost. The methods employed include transmission of a high-frequency resolution spectral envelope and a novel forward/backward adaptive bit allocation algorithm. In order to satisfy practical requirements of an emissions coder, the syntax includes a number of features useful to broadcasters and consumers: loudness uniformity between programs; dynamic range control; and broadcaster control of downmix coefficients. Optimum application of the system involves the creation and delivery of metadata describing dialogue loudness and intended dynamic range.

Dolby Digital Audio Delivery to the Consumer

The Dolby Digital (AC-3) audio coding system is the means to deliver high quality multichannel audio to the consumer. The system is used by many media, including LaserDisc, DVD, cable, satellite and terrestrial DTV. This paper will present an overview of the Dolby Digital coding system, and delineate the important features which ensure that high quality program content can be delivered to, and meet the needs of, a wide range audience of listeners with differing requirements in audio presentation.

Distribution and Emission of Multichannel Audio Programs, and Implications for Post-Production

Many new digital television emission formats, including digital video disk (DVD), community antenna TV (CATV), direct broadcasting by satellite (DBS), and terrestrial television, incorporate the Dolby Digital (AC-3) low bit-rate audio coding system. This system is capable of delivering discrete multichannel audio to the consumer, and also offers several unique features such as dialogue normalization and dynamic range control. The Dolby Digital is intended for use in emission, which is defined as the final link in the delivery path to the consumer Many of the features of Dolby Digital are best controlled in the post-production process. A distribution path is required between the output of post-production and the input to the final AC-3 emission encoder Although the handling of multichannel audio is routine in the post-production area, the infrastructure needed to distribute multichannel audio in the broadcast environment is currently lacking. This paper will describe some of the unique features of Dolby Digital that should be understood and managed by those in post-production. The paper also illuminates some of the problem areas in distribution of the completed multichannel audio program to the actual point of emission to the final consumer.

AC-3 audio coder

AC-3 is a system for coding up to 3.1 channels of audio into a low bit-rate data stream. High quality may be obtained with compression ratios approaching 12-1 for multichannel audio programs. The high compression ratio is achieved by methods which do not increase decoder memory, and thus cost. The methods employed include: the transmission of a high frequency resolution spectral envelope; and a novel forward/backward adaptive bit allocation algorithm. In order to satisfy practical requirements of an emissions coder, the AC-3 syntax includes a number of features useful to broadcasters and consumers. These features include: loudness uniformity between programs; dynamic range control; and broadcaster control of downmix coefficients. The AC-3 coder has been formally selected for inclusion in the U.S. HDTV broadcast standard, and has been informally selected for several additional applications.