This correspondence discusses a new method for designing the prototype filters necessary to implement M-band pseudo QMF banks, This method does not rely on the traditional nonlinear optimization used in past work but ...
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This correspondence discusses a new method for designing the prototype filters necessary to implement M-band pseudo QMF banks, This method does not rely on the traditional nonlinear optimization used in past work but rather optimizes a single parameter on a convex error surface, consistently delivering the best equiripple filter possible while minimizing the overlapped passband distortion.
Typical parameters of wideband speech and audio signals, including digitized versions of each, potential applications, and available transmission media, are described. Facts about human auditory perception that are ex...
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Typical parameters of wideband speech and audio signals, including digitized versions of each, potential applications, and available transmission media, are described. Facts about human auditory perception that are exploited in audio coding and quality measures that play an important role in coder evaluations and designs are reviewed. Techniques for efficient coding of wideband speech and audio signals, with an emphasis on existing standards, are discussed. The audio coding standard developed by the Moving Pictures Expert Group within the International Organization for standardization (ISO/MPEG) is covered in some detail, since it will be used in many application areas, including digital storage, transmission, and broadcasting of audio-only signals and audiovisual applications such as videotelephony, videoconferencing, and TV broadcasting. Ongoing research and standardization work is outlined.< >
The MPEG-2 systems specification describes how MPEG-compressed video and audio data streams may be multiplexed together to form a single data stream. This paper aims to introduce the jargon and the fundamental princip...
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The MPEG-2 systems specification describes how MPEG-compressed video and audio data streams may be multiplexed together to form a single data stream. This paper aims to introduce the jargon and the fundamental principles of the MPEG-2 systems layer. Two alternative multiplexing methods are specified for the MPEG-2 systems layer. The "programme stream" is biased towards the storage and replay of a single programme from a digital storage device while the "transport stream" is intended for the simultaneous delivery of a number of programmes over potentially error-prone channels. Both methods facilitate the inclusion of programme specific information detailing the programme(s) and elementary streams present. Both methods use a system of time stamps and clock references to ensure the synchronous replay of related elementary streams and correct buffer behaviour at a decoder. There are many optional syntax elements and many opportunities to include private (user-defined) syntax extensions enabling either multiplexing to be optimised to suit a particular application.
The Moving Pictures Expert Group (MPEG) was started in 1988 as a working group within ISO/IEC with the aim of defining standards for digital compression of audio-visual signals. The MPEG's first aim was to define ...
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The Moving Pictures Expert Group (MPEG) was started in 1988 as a working group within ISO/IEC with the aim of defining standards for digital compression of audio-visual signals. The MPEG's first aim was to define a video coding algorithm for application on digital storage media, in particular for CD-ROM. Very rapidly the need for audio coding was added and the scope was extended from being targetted solely on CD-ROM to trying to define a generic algorithm capable of being used by virtually all applications, from storage-based multimedia systems, television broadcasting, and communications applications such as video-on-demand to face-to-face communication. The MPEG's first project, MPEG-1, was published in 1993 as ISO/IEC 11172. It is a three part standard defining audio and video compression coding methods and a multiplexing system for interleaving audio and video data so that it can be played back in close synchronisation. During 1990, the MPEG recognized the need for a second, related standard for coding video at higher data rates in an interlaced format (the essential technical difference is that MPEG-1 is designed for coding progressive pictures whereas MPEG-2 is optimised for interlaced pictures, MPEG-1 bit-streams are decodable on MPEG-2 decoders). The MPEG-2 standard is capable of coding standard definition television at bit-rates from about 4-9 Mbit/s and high definition television at 15-25 Mbit/s. For interlaced video signals coded at bit rates above about 3 Mbit/s, MPEG-2 is more efficient than MPEG-1. MPEG-2 audio is backwards compatible with MPEG-1 audio and extends the system to multi-channel surround sound coding.
Digital audio compression and SCPC (single channel per carrier) technologies permit efficient distribution of audio and data to a network of radio stations using small antennas. Transmitting the SCPC signals on the ba...
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Digital audio compression and SCPC (single channel per carrier) technologies permit efficient distribution of audio and data to a network of radio stations using small antennas. Transmitting the SCPC signals on the band-edge of a video transponder can be a cost-effective way of providing the space segment. This paper describes the design phase and the results of implementing band-edge SCPC carriers on an analog-video transponder. Before attempting an operational test, Comsat Laboratories investigated the proposed configuration using the Comsat C-band transponder simulator. The simulation tests showed that the SCPC signals are more efficient than video subcarriers in use of transponder power and validated that band-edge SCPC could be achieved without degrading the analog video signal. The transponder can be operated into saturation. The actual implementation of the video and SCPC system required careful tradeoffs in the operating power of the video and the SCPC signals because of the power demands of the video signal and the need to operate in the nonlinear portion of the transponder. The system has been operating for more than a year. Three digital SCPC carriers, each with a FM-quality, stereo audio program, are received with 2.4 meter antennas throughout South America. VOA is now investigating digital-audio SCPC's operating with digital-video carriers on the same transponder. Preliminary results are also given here.< >
With the rapid move towards a 'tapeless' environment the professional audio industry, and that includes broadcasting, is continually seeking ways to adapt digital technology for high quality audio. The techniq...
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With the rapid move towards a 'tapeless' environment the professional audio industry, and that includes broadcasting, is continually seeking ways to adapt digital technology for high quality audio. The technique of compressing digital audio and the ability to dial-up, on demand, a high quality audio circuit, defining the bandwidth limits, be it for speech or music, mono or stereo, has very clear economical and practical advantages for potential users. Developments in bit rate reduction and the increasingly available ISDN network, both nationally and internationally, have the potential to alleviate many of the problems associated with traditional analogue circuits. The author discusses the use of ISDN for audio broadcasts and the compression of the audio signal. Codec selection and compatibility are also discussed.< >
This paper contains the description of the system manager, one part of the demonstrator constructed during the third year of the MAVT project funded through the RACE program by the EEC. The system manager is the centr...
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This paper contains the description of the system manager, one part of the demonstrator constructed during the third year of the MAVT project funded through the RACE program by the EEC. The system manager is the central control unit of the demonstrator with interfaces to the user interface, the DECT radio system, the video codec, and to the audio codec. Additional to the control functions, this unit performs the synchronisation and the multiplexing and demultiplexing of the data streams. The hardware platform is an universal signal processor board, based on a TMS320C40 processor, with an I/O module including two serial synchronous interfaces.< >
Although shortwave radio continues to be invaluable for penetrating closed countries, it is totally unsuitable for the distribution of high-quality stereo programming for rebroadcast on FM radio. Satellite digital aud...
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Although shortwave radio continues to be invaluable for penetrating closed countries, it is totally unsuitable for the distribution of high-quality stereo programming for rebroadcast on FM radio. Satellite digital audio distribution provides the solution. State-of-the-art digital audio compression techniques make it possible to send high-fidelity stereophonic signals over increasingly narrow bandwidths. International satellites can deliver these signals to large areas of the globe, utilising digital encoding techniques to reduce the required transmit power to an absolute minimum. The America Latina via Satellite (ALAS) project was conceived to utilise these resources to fulfill the programming requirements of Latin America's young urban population. The ALAS network has been designed to provide a pseudo-interactive satellite distribution network.< >
In the past decade a lot of work was dedicated to the difficult issue of data compression both for video and audio. For digital storage media, ISO/IEC JTCI/SC29/WGII alias MPEG (Moving Pictures Expert Group) succeeded...
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In the past decade a lot of work was dedicated to the difficult issue of data compression both for video and audio. For digital storage media, ISO/IEC JTCI/SC29/WGII alias MPEG (Moving Pictures Expert Group) succeeded in finding a common consensus among all the solutions and principles in order to finalist: a generic coding method for moving pictures and associated audio at up to about 1.5 Mbit/s. In November 1992. a new international standard consisting of three distinct parts, audio, video and system, was issued by MPEG: IS-11172 or MPEG1 standard. This paper introduces the main characteristics of this new standard concerning the audio part and mainly concentrates on the so-called MUSICAM family which concerns the first two audio layers. We first recall MPEG1-audio main features and then we present the extension to the half sampling rates and to multichannel coding.
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