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BBC Research and Development Reports

A collection of BBC Research and Development reports and white papers, dating from the 1960s through to 1996.

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R&D Report 1996-07 : EUREKA 147: Subjective assessment of the error performance of the DAB system, including tests at 24 kHz audio sampling frequency. M. Lever (CCETT), J. Richard (CCET), N.H.C. Gilchrist This Report describes tests carried out by the authors and other members of Eureka 147 Working Group âAâ, to assess the performance of the DAB (Digital Audio Broadcasting) system with a low carrier-to-noise ratio at the receiver. The tests were conducted using a number of listeners to...
Topics: uep, mono, stereo, joint, audio, tests, rayleigh, eep, onset, impairment, bit rate, rural rayleigh,...
R&D Report 1996-06 : The Crystal Palace FM filler experiment R.H. Evans, A.J. Bower In some areas of London, listeners to BBC Radio National FM services had suffered from poor reception for some time. The problem was particularly severe immediately south of the River Thames where around one million people suffered with unsatisfactory reception on portable and car receivers. This was due to path blocking of the direct signal from the BBCâs Wrotham transmitter, located several miles south...
Topics: wrotham, crystal, filler, palace, mhz, transmitter, frequency, khz, transmitters, offset, khz...
R&D Report 1996-02 : MPEG-2: Overview of the systems layer P.A. Sarginson The MPEG-2 Systems specification describes how MPEG-compressed video and audio data streams may be multiplexed together with other data to form a single data stream suitable for digital transmission or storage. This Report introduces the principles and terminology of the MPEG-2 Systems layer. The Report covers three main areas: Firstly, the structure of the multiplexes; secondly, the service information that may be...
Topics: elementary, stream, buffer, coder, programme, access, transport, decoder, video, streams,...
R&D Report 1996-14 : WTDM Pilot Installation. A report on the work of RACE Project 2001 C.D. Mathers (editor) The BBC has led two RACE-sponsored projects to develop the technology for a fibre-optic based video signal router. In the first project, R1036, prototype equipment was developed; a demonstration in 1992 showed that optical routeing was not only feasible, but could accommodate different signal formats such as serial digital 625-line and uncompressed EU-95 HDTV. In a second RACE...
Topics: optical, wavelength, wtdm, network, pilot, nrk, installation, routeing, demultiplexer, equipment,...
R&D Report 1996-08 : The COFDM Modulation system: The heart of Digital Audio Broadcasting. P. Shelswell Digital audio broadcasting offers the potential to give every radio in Europe the sound quality of a compact disc. To accomplish this, it requires a rugged method of transmission. The coded orthogonal frequency division multiplexing (COFDM) modulation system was developed to meet this need. This Report describes the reasons why a new modulation process was needed, and explains how the...
Topics: symbol, cofdm, signal, frequency, bbc, modulation, carriers, digital, dab, fourier, modulation...
R&D Report 1996-03 : MPEG video coding: A basic tutorial introduction S.R. Ely MPEG has been outstandingly successful in defining standards for video compression coding, serving a wide range of applications, bit-rates, qualities and services on a worldwide basis. The standards are based upon a flexible toolkit of techniques for bit-rate reduction. MPEG video coding uses a combination of motion-compensated interframe prediction (for reducing temporal redundancy) with Discrete Cosine...
Topics: prediction, dct, coding, picture, macroblock, coded, quantisation, mpeg, frame, coder, video...
R&D Report 1996-09 : A comparison of motion-compensated interlace-to-progressive conversion methods G.A.Thomas The conversion of interlaced video to progressive format may be carried out in a number of ways, including simple vertical interpolation, fixed or motion-compensated vertical-temporal interpolation, and approaches based on motion compensation using non-uniform sampling theory. Motion-compensated methods are the only ones which offer the possibility of maintaining high vertical...
Topics: vertical, filter, field, vectors, vector, filters, motion, temporal, errors, picture, motion...
R&D Report 1996-04 : ISO/IEC MPEG-2 AUDIO: Bit-rate-reduced coding for two-channel and multichannel sound. G. Stoll, N.H.C. Gilchrist Since 1988 the ISO/IEC Moving Picture Expertsâ Group (MPEG) has been developing generic coding standards for video and audio, mainly for broadcast and multimedia applications. The MPEG audio standard (ISO/IEC 11172-3) was finalised in November 1992. It follows a three-layer structure in order to fulfil the requirements of various applications. Good audio...
Topics: audio, coding, multichannel, sound, layer, sampling, stereo, digital, frequency, compatibility,...
R&D Report 1996-10 : Radio with Pictures - A new medium R.H.Evans The advent of digital radio broadcasting provides the broadcaster with the opportunity to convey a variety of data types, to considerably enhance a basic audio service. Analogue FM broadcasts already benefit from a variety of features from the Radio Data System (RDS), but while RDS uses an additional carrier to convey this digital data, the emerging all-digital services such as Eureka DAB, Inmarsat IDDS and WorldSpace, have...
Topics: rwp, audio, pictures, programme, news, data, inmarsat, picture, receiver, radio, television news,...
R&D Report 1996-12 : Mobile Broadband System. A report on the work of RACE Project 2067. J.T. Zubrzycki Mobile Broadband System (MBS) is a wireless cellular radio network capable of carrying digital signals at bit rates sufficient for digital video, including compressed HDTV. The technological feasibility has been studied in RACE* Project 2067 MBS, which had the aim to extend the Broadband Integrated Services Digital Network (B-ISDN) to mobile users, providing much higher capacity to users...
Topics: mbs, mobile, ghz, base, broadband, demonstrator, antennas, antenna, project, diversity, diversity...
R&D Report 1996-11 : Motion estimation for MPEG-2 coding using 'true' vectors G.A.Thomas The motion estimator is a key component of any MPEG-2 video coder. It is common practice to use a method based on block-matching, which generates vectors designed to yield good predictions of images to be coded, without regard for whether the vectors correspond to actual motion. This Report describes a method of deriving motion vectors for an MPEG-2 coder from a motion estimator designed to produce...
Topics: vectors, vector, refinement, field, coding, traced, pixel, tracing, sequences, motion, vectors...
R&D Report 1996-01 : Advanced PAL dcoding: Exploration of some adaptive techniques. J.O. Drewery The need for improved decoding of conventional PAL in the broadcast chain is first established, in the context of future developments. The work done on this subject in the last twenty years is then reviewed, concluding that currently available decoders, while generally demonstrating a high level of performance, are nevertheless still capable of further improvement. Software simulations of two...
Topics: pal, chrominance, signal, vertical, picture, decoder, signals, luminance, adaptive, motion,...
R&D Report 1996-13 : PlanTx: The universal tool for digital and analogue transmitter planning M.P.Shovelton Terrestrial radio-frequency planning is undergoing a revolution. With the movement of broadcasters towards digital transmission, the RF planning book is being re-written. The design of digital transmitter networks demands new techniques and innovative new prediction tools in order to allow these networks to be accommodated within the already tightly-packed broadcast spectrum (that is,...
Topics: transmitter, matrix, interference, digital, transmitters, plantx, analogue, terrain, bbc,...
BBC Research and Development Reports
1996 J.T. Zubrzycki, R.H. Evans, P. Shelswell, M.A. Gamma, M. Gutierrez
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R&D Report 1996-05 : Experimental satellite broadcast of Eureka 147 DAB from Solidaridad 2 J.T. Zubrzycki, R.H. Evans, P. Shelswell, M.A. Gamma, M. Gutierrez BBC Research and Development Department, in collaboration with Telecomunicaciones de Mexico and the Instituto Mexicano de Comunicaciones, has carried out highly successful test transmissions of the Eureka 147 Digital Audio Broadcasting (DAB) system in Mexico from the Solidaridad 2 satellite from 17 to 21 July 1995. This included tests...
Topics: satellite, dab, solidaridad, antenna, transponder, mobile, eureka, signal, power, broadcasting,...
R&D Report 1995-07 : Further investigations of partitions having built-in acoustic treatment. G.D. Plumb Laboratory measurements were made of the sound insulations and absorption coefficients of a range of metal-framed partitions having built-in acoustic treatment. The partitions were made using glass wool and gypsum boards. The sound insulations of the single leaf partitions having built-in acoustic treatment were considerably lower than those of comparable partitions made using mineral...
Topics: partitions, mineral, partition, glass, insulations, unperforated, perforated, wool, absorption,...
R&D Report 1995-08 : Low-delay predictive audio coding for the HIVITS HDTV codec A.K. McParland, N.H.C. Gilchrist This Report describes the work on predictive audio coding carried out by the BBC as part of the RACE âHIVITSâ project. The purpose of the work was to develop and demonstrate a low bit-rate audio codec with low delay for use with a digital HDTV (high definition television) signal coded by the HIVITS HDTV codec and capable of conveying at least 5 channels of audio within the...
Topics: audio, coding, predictors, hdtv, prediction, predictive, hivits, codec, coder, error, dsp dsp,...
R&D Report 1995-15 : The effects of frequency errors in OFDM J.H. Stott An OFDM system can suffer from two types of frequency error: firstly, a frequency offset (as might be caused by the tolerance of the local=oscillator (LO) frequency); secondly, an error in the receiver mast clock frequency (which will cause the spacing of the demodulating carriers to differ from those transmitted, and the duration of the receiver integrate-and-dump process to differ from the reciprocal of the...
Topics: carriers, frequency, carrier, error, symbol, offset, ofdm, ici, receiver, variation, demodulating...
R&D Report 1995-12 : Archive retrieval: Techniques for image enhancement J.C.W. Newell This report describes image processing techniques which could be used to improve the perceived resolution of archive video recordings. It has been found that the benefits obtained using linear methods are limited. However, a non-linear method is described which can be used to sharpen edges. The technique has been used successfully to enhance images with a significantly smaller visible increase in ringing...
Topics: signal, process, linear, frequency, filter, correction, edges, sharpening, noise, edge, aperture...
R&D Report 1995-11 : Line Shuffling: Development of a scrambling system for terrestrial UHF television broadcasts. A.J. Bower, C.K.P. Clarke, A.P. Robinson This Report describes the development of a scrambling system for overnight downloading of television programmes to video cassette recorders â the BBC Select service. The scrambling techniques used successfully for many years for satellite broadcasting and cable distribution are often unsuitable for UHF terrestrial broadcasting using...
Topics: scrambling, signal, scrambled, bbc, signals, terrestrial, lines, shuffling, rotation, block,...
R&D Report 1995-14 : Digital HDTV bit-rate reduction in the studio T. Vlachos, M.G. Croll Two novel source coding algorithms are presented which are suitable for the recording of digital High Definition Television signals. One of the bit-rate reduction schemes is based on the Wavelet Transform and the other on the Lapped Orthogonal Transform (LOT). According to the first scheme, a multi-layered, hierarchical description of the source signal is obtained by means of a quad-tree, half-band...
Topics: coding, wavelet, transform, quantiser, block, quantisation, digital, frequency, compression,...
R&D Report 1995-02 : Digital Audio Broadcasting: Measuring techniques and coverage performance for a medium power vhf single frequency network M.C.D. Maddocks, I.R. Pullen, J.A. Green The advent of digital formats such as CD has created demand for uniformly high audio quality from radio. In order to provide such high-quality stereo reception, a Digital Audio Broadcasting (DAB) system capable of reliable reception in vehicles and on portables has been developed by the European EUREKA 147...
Topics: dab, signal, coverage, measurements, transmitter, locations, transmitters, audio, strength, system,...
R&D Report 1995-10 : A method for the calculation of tolerances for display primary chromaticity coordinates. A. Roberts The manufacturers of displays for television and other visual display systems are rarely given sufficient information to ensure that their products perform satisfactorily. Typically, parameters such as the peak brightness and primary chromaticities, transfer characteristic and illumination uniformity are supplied, but this information is usually generic, it does not refer...
Topics: ebu, error, tolerances, primaries, zones, vertex, primary, tolerance, extrinsic, colour, primary...
R&D Report 1995-06 : Lightweight partitions having improved low frequency sound insulations. G.D. Plumb The sound insulations were measured of a range of single, double and triple leaf partitions. For the single leaf partitions, a staggered stud configuration was used. For the double and triple leaf partitions, the configuration of the boards was different from that in the conventional Camdens. At low frequencies, the partitions tested generally had higher sound insulations than comparable...
Topics: partition, insulations, sound, leaf, wool, triple, camden, partitions, insulation, double,...
R&D Report 1995-05 : Controlled Image Designs: Results from the first installations R. Walker Following successful evaluation of the experimental installation, the principle was used in the BBC as the basis for the design of three refurbished control rooms in Broadcasting House, London and one new control room for the Transcription Service in Bush House. The results of acoustic tests from these areas are presented. The problems of reflections from the top surfaces of mixing desks are also...
Topics: loudspeaker, response, reflections, frequency, msec, design, reflection, acoustic, cubicle,...
R&D Report 1995-01 : Modular acoustic diffuser: The development and performance of a modular acoustic diffuser. R. Walker, M.D.M. Baird The development of a prototype modular acoustic diffuser into a commercially reproducible product is described. The difficulties with materials, manufacturing processes and with fire-safety considerations are discussed. Acoustic measurements carried out on the final production modules showed that the diffuser met the acoustic requirements, despite...
Topics: diffuser, acoustic, absorption, modular, response, receiver, bbc, reflection, measurement,...
R&D Report 1995-09 : A television colorimetry: A tutorial for system designers. A. Roberts This Report was written primarily for use as a colorimetry tutorial for any MPEG users who may feel confused by the plethora of descriptive data contained in the MPEG data-stream. It is not intended to be an exhaustive treatise on basic colorimetry or even on television colorimetry; that would require a very much larger document. There are many books on the subject, but two are of particular...
Topics: signals, luminance, matrix, chroma, primaries, camera, linear, colour, display, equations, rgb...
R&D Report 1995-04 : Controlled Image Design: The management of stereophonic image quality R. Walker Historically, the basis for the acoustic design of control rooms for stereophony has been the reduction of discrete reflections by means of sound absorption. As an alternative, the use of non-absorbent surfaces to direct early reflections away from the listener makes it possible to obtain good stereo image sharpness without making a âdeadâ acoustic environment. It also makes the...
Topics: acoustic, reflections, design, sound, reflection, reverberation, control, room, prototype,...
R&D Report 1995-03 : Controlled Image Design: The measurement of Time-Frequency responses. R. Walker This Report describes the measurement of acoustic events in a 3-dimensional measurement domain. An outline of the general theoretical background is followed by a description of the special requirements for the measurement of short-term acoustic responses in rooms. The results of measurements on an experimental synthesis of a single room reflection are also presented. It is shown that the...
Topics: frequency, response, fourier, measurement, transform, impulse, reflection, signal, responses,...
R&D Report 1995-13 : Evaluations of high quality, multichannel audio codecs carried out on behalf of SO/IEC MPEG. D.J. Meares BBC R&D has been conducting audio tests for and on behalf of ISO/IEC MPEG since 1973. This report summarises the more important of those tests and the methods used for the assessments. Systems tested include MPEG-2 Layers II and III, as well as the more recent Non-Backwards Compatible codecs. It is reported that the optimisation is still in progress.
Topics: mpeg, coding, layer, audio, codecs, tests, iii, codec, nbc, test, moving pictures, harp mane, layer...
R&D Report 1994-10 : Digital video compression: Standardisation of scalable coding schemes. P.N. Tudor, N.D. Wells Scalable coding schemes for bit-rate reduction of digital TV, including HDTV, are being considered in order to provide for compatibility with lower resolution scanning formats and to provide for graceful degradation of the picture quality in the presence of transmission errors. This report describes some of the scalable coding schemes considered within the Moving Pictures...
Topics: scalable, layer, lower, decoded, frequency, coefficients, prediction, dct, coder, upper, layer...
R&D Report 1994-14 : The sound insulations of studio doors: Part 1: Door Blanks G.D. Plumb, R. Clark The sound insulations of a range of different door blanks were measured. The results were compared with the sound insulations of existing BBC door blanks. The new doors were made from medium density fibreboard (MDF) which is more stable than the blockboard used in existing studio doors. Consequently, they should require less maintenance and adjustment and should have a longer lifespan. The...
Topics: mdf, door, insulations, bitumen, damping, measured, bbc, sound, acoustic, lightweight, band centre,...
BBC Research and Development Reports
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R&D Report 1994-12 : A wideband absorber for television studios. M.D.M. Baird The acoustic treatment in BBC television studios has taken various forms to date, all of which have been relatively expensive, some of which provide inadequate absorption. An investigation has been conducted into the possibilities of producing a new type of wideband absorber which, would be more economic, also taking installation time into account, than earlier designs. This Report describes the absorption...
Topics: absorption, absorber, wideband, frequency, acoustic, mineral, bbc, zintec, weldmesh, absorbers,...
R&D Report 1994-09 DAB : Multiplex and system support features J.L. Riley This report describes the multiplex and system support features of the Eureka 147/DAB* digital audio system. It sets out the requirements of all users along the broadcast chain from service providers and broadcaster through to the listener. The contents of the transmission frame are examined, drawing the distinction between the main service multiplex and the provision of control information in a separate fast data...
Topics: multiplex, dab, audio, receiver, features, bbc, channel, data, main service, feature, programme...
R&D Report 1994-02 : Bit-rate reduction of digital television for transmission: An introductory review. N.D. Wells This report is based on a BBC tutorial paper describing several bit-rate reduction techniques which have been studied at the BBC and which are used for the transmission of digital television signals. The techniques described are Sample-Rate Reduction, Differential Pulse Code Modulation (DPCM) coding - including a review of linear prediction theory and quantisation, Transform...
Topics: sampling, coding, prediction, quantiser, dpcm, buffer, transform, signal, frequency, coder, colour...
R&D Report 1994-05 : Maximal-length sequence methods: Acoustic measurements in the presence of high levels of extraneous noise. R. Walker The use of the maximal-length sequence method to measure acoustic responses in the presence of high levels of extraneous noise is described. Direct and reliable measurements of time and frequency response functions down to a signal-noise ratio of 0 dB are possible. With modest amounts of signal-averaging, response functions down to S/N ratios of -20 dB...
Topics: measurement, frequency, measurements, impulse, signal, response, noise, sequence, averaging,...
R&D Report 1994-15 : The sound insulations of studio doors: Part 2: Door seals G.D. Plumb, R. Clark The acoustic performances of a range of proprietary acoustic door seals were measured in the Transmission Suite. The seals were fitted to a standard BBC lead-cored door hung in a purpose-built blockwork wall. As a result of the work, suitable plant-on magnetic perimeter seals and drop-down threshold seals are recommended. The use of these seals will simplify the existing door frame design and...
Topics: seals, threshold, perimeter, fitted, raven, insulations, magnetic, door, compression, bbc, octave...
R&D Report 1994-06 : Acoustic noise criteria for listening rooms and control rooms R. Walker This report is based on a submission document to both EBU G1(LIST) and ITU-R TG 10/3 drafting committees. It describes background noise criteria for high-quality listening environments from a number of different organisations and the derivation of a compromise criterion for the continuous background noise levels. The outcome of the work, and the proposal submitted to those technical groups, was the...
Topics: noise, octave, curves, bbc, iso, oirt, rating, criteria, noise rating, curve, listening rooms, band...
R&D Report 1994-01 : Implementation of amplitude modulation companding using a digital signal processor. C.R.Nokes BBC Amplitude Modulation (AM) radio transmissions have for some time been using amplitude modulation companding (AMC) - a method of companding whose purpose is to reduce the costs of transmission whilst maintaining, as far as possible, the audibility of the radio service. AMC is one form of compression of AM transmissions more generally called dynamic carrier control (DCC). The...
Topics: signal, compression, modulation, amplitude, amc, bbc, carrier, dsp, enhancement, transmitter,...
R&D Report 1994-11 : High frequency room responses : Acoustic design and the control of stereophonic image quality R. Walker Aspects of mid and high frequency acoustic design are described, mainly in the context of relatively small rooms. The factors affecting the design and some of the difficulties which may be encountered are also discussed. The primary means of evaluating the quality of reproduced sound is the studio control room (and its associated equipment). This Report is written...
Topics: acoustic, sound, absorption, frequency, surfaces, reflections, design, reverberation, diffuse, bbc,...
R&D Report 1994-03 : Measurements of wideband multipath propagation at 531MHz and 1.265GHz C.P. Bell, P.J. Brightwell, P.J. Brightwell, R.F. Rudd, W.F. Williams Multipath propagation measurements and their analyses are described. The work was carried out by the BBC over the period 1988 - 1990 as a contribution to the Eureka 147 Project, with the aim of providing statistical data required in the configuration of a Digital Audio Broadcast system. Two different areas were chosen for the tests,...
Topics: mhz, delay, bbc, measurements, croydon, urban, ghz, multipath, frequency, propagation, correlation...
R&D Report 1994-16 : Digital Audio Broadcasting: Comparison of coverage at Band II and Band III. I.R. Pullen, P.J. Doherty, M.C.D. Maddocks A Digital Audio Broadcasting (DAB) system capable of reliable reception in vehicles and portables has been developed by the EUREKA 147 project. This Report describes a set of experiments performed to compare the coverage area when radiating a DAB signal of equal power in Band II and Band III. It is concluded that a slightly lower level of signal...
Topics: band, dab, signal, iii, variation, mhz, transmitter, coverage, map, bbc, transmitting equipment,...
R&D Report 1994-13 : DRACULA: Dynamic range control for broadcasting and other applications. N.H.C. Gilchrist The BBC has developed a digital processor which is capable of reducing the dynamic range of audio in an unobtrusive manner. It is ideally suited to the task of controlling the level of musical programmes. Operating as a self-contained dynamic range controller, the processor is suitable for controlling levels in conventional AM or FM broadcasting, or for applications such as the...
Topics: dynamic, gain, range, digital, signal, controller, compression, audio, processor, broadcasting,...
R&D Report 1994-07 : Further measurements of the sound insulations of metal-framed partitions. G.D. Plumb The sound insulations were measured of a number of single and double leaf metal-framed partitions. The purpose of the work was to develop alternative designs for partitions to that of the Camden. The Camden contains fibreboard as one of its constituent elements. The new partitions used plasterboard as the sole board material. Therefore, the new partitions were heavier than the...
Topics: partition, partitions, insulations, plasterboard, wool, narrow, leaf, sound, camden, insulation,...
R&D Report 1994-08 : The sound insulations of metal-framed partitions having structural loadbearing properties. G.D. Plumb The sound insulations were measured of several single and double leaf partitions. The partitions had metal frames and were capable of supporting significant structural loads. The purpose of the work was to design structural partitions that were cheaper to build than the existing masonry walls used for the construction of large studios. For some of the double leaf tests,...
Topics: structural, partition, leaf, sound, blockwork, cavity, insulations, partitions, shaftwall,...
R&D Report 1994-18 : Eureka 147: Tests of the error performance of the DAB system N.H.C. Gilchrist This Report describes tests carried out by the BBC and other members of the Eureka 147 Working Group 2-A, to assess the performance of the DAB (Digital Audio Broadcasting) system with a low carrier-to-noise ratio at the receiver. The tests were conducted using a number of listeners to judge the audio quality, making collaborative decisions with the knowledge of the conditions under which the...
Topics: code, rate, stereo, onset, rayleigh, fading, failure, impairment, dab, ratios, simulated rayleigh,...
R&D Report 1994-04 : Multi-channel sound for HDTV: Subjective tests on sound channel configuration J.A. Fletcher This report describes subjective tests carried out as part of the Eureka 95 project to compare different multi-channel sound systems being considered for use with HDTV. In the tests, the number of sound channels varied from one (mono) to five (three front channels and two surround channels). The improvement in quality obtained by increasing the number of front channels from two...
Topics: zirkus, knie, preference, surround, acrobats, vilia, tipsy, listeners, sound, eliott, knie peg,...
R&D Report 1994-17 : Com3: A Composite-Compatible Component coding system G.A. Thomas This Report describes a method for conveying a component video signal on a single cable in such a way that it may be passed through any existing composite studio equipment that has a bandwidth of approximately 9 MHz. The system was originally termed Extended Studio PAL, although it is now referred to as Composite-Compatible Component (Com3, Com cubed) in order to emphasise the quality difference it offers...
Topics: signal, chrominance, luminance, vertical, ntsc, frequency, coded, pal, filter, horizontal,...
R&D Report 1993-12 : Predicted coverage of a COFDM Single Frequency Network for UHF digital terrestrial TV broadcasting M.B.R. Lee The Coded Orthogonal Frequency Division Multiplex (COFDM) transmission system provides a very high degree of tolerance towards multipath interference. Three factors contribute towards this tolerance; the inclusion of a guard interval, coding to provide error correction and the division of the digital data amongst a very large number of low bit rate carriers. It...
Topics: coverage, antenna, guard, digital, field, directional, interval, transmitters, bbc,...
R&D Report 1993-06 : Metal-framed partitions with reduced thicknesses: Part 2 -- Built-in acoustic treatment. G.D. Plumb Laboratory measurements were made of the sound insulations and absorption coefficients of a range of metal-framed partitions having built-in acoustic treatment. The optimum constructions for single and double leaf absorbent partitions had marginally lower sound insulations (approximately 1 dB) than those of comparable single and double metal-framed Camdens. The effective...
Topics: partitions, absorption, partition, sound, insulation, unperforated, perforated, leaf, acoustic,...
R&D Report 1993-11 : Digital Audio Broadcasting: comparison of coverage at different frequencies and with different bandwidths. M.C.D. Maddocks, I.R. Pullen A Digital Audio Broadcasting (DAB) system capable of reliable reception in vehicles and portables has been developed by the Eureka 147 project. This report describes a set of experiments performed to investigate the effect on the coverage area of changing the bandwidth of the DAB signal and its transmit frequency band. It is concluded...
Topics: mhz, bandwidth, dab, signal, band, frequency, coverage, cofdm, antenna, digital, location...
R&D Report 1993-04 : Alleviation of co-channel interference at Poole relay station J.H. Moore, A.I.E. Booker The Rowridge UHF television transmitting station, situated on the Isle of Wight, radiates the four principal UK domestic television channels to the south coast of England, and provides an off-air feed to a number of dependent relays. At one relay station (Poole), occasional Co-channel Interference (CCI) is known to occur. It is particularly noticeable during the summer and autumn...
Topics: offset, precision, channel, rowridge, relay, frequency, poole, interference, impairment, cci, total...
R&D Report 1993-05 : Metal-framed partitions with reduced thicknesses: Part 1 -- Narrower studs and cavities. G.D. Plumb The sound insulations were measured, in the Research Department Transmission Suite, of ten different metal-framed partitions. These partitions had narrower cavities and metal studs than those of the conventional thickness metal-framed Camden. Mineral wool had been installed in the cavities of some of the partitions and some partitions had double plasterboard skins rather...
Topics: sound, partitions, partition, studs, mineral, leaf, insulations, insulation, plasterboard, double,...
R&D Report 1993-09 : The HDTV digital audio matrix A.J. Mason Multichannel sound systems are being studied as part of the Eureka 95 and Radio-communication Bureau TG10-1 investigations into High Definition Television. One emerging sound system has five channels; three at the front and two at the back. This raises some compatibility issues. The listener might have only, say, two loudspeakers or the material to be broadcast may have fewer than five channels. The problem is how best to produce...
Topics: matrix, digital, audio, signal, inputs, hdtv, transputer, analogue, dsp, channel, channel status,...
R&D Report 1993-08 : Optimum dimension ratios for studios, control rooms and listening rooms. R. Walker Most control rooms, listening rooms and small studios have dimensions that become comparable with the wavelength of the sound within the normally accepted audio range. Standing waves, where one of the room dimensions is an integer multiple of half the wavelength of the sound energy, result in irregular frequency responses. The response will also be a strong function of position of both...
Topics: room, rooms, criterion, proportions, values, quality, modes, height, mode, bbc, dimension ratios,...
R&D Report 1993-15 : Final Report of RACE Project 1036: WTDM Broadband Customer Premises Network. A. Oliphant, C.D. Mathers Discussions in 1985 with BBC Television showed that signal routeing in broadcasting centres presented two problems which would become more severe in the future: first, the increasing requirement for all sources to be available at all destinations, and second, the impending proliferation of signal standards (e.g. digital component signals, HDTV). The solution proposed...
Topics: optical, laser, broadband, project, wtdm, race, demultiplexer, wavelength, coupler, bbc, broadband...
R&D Report 1993-13 : The development of the switched-horn radio-camera system R.H. Evans, C.E. Melvin, J.T. Zubrzycki Radio-cameras are now well established at outside broadcast events (OBs) but conventional circularly polarised antennas and electromechanical tracking systems still leave considerable room for improvement. A new radio-camera system is described which uses a cluster of six directional transmitting antennas, with each antenna pointing in a different direction. Test signals...
Topics: horn, multipath, signal, antenna, video, sync, system, camera, separator, test, horn selection,...
R&D Report 1993-14 : RINSE: a digitally implemented flywheel sync regenerator for improved video synchroniser performance. R.H.Evans Microwave links are widely used at live outside broadcast events for carrying video signals from mobile cameras such as those carried on the shoulder or fitted to vehicles. A digital frame store synchroniser is required when using a remote radio-camera and this has caused additional problems with variable quality signals. During moments of weak signal strength...
Topics: sync, rinse, video, noise, syncs, synchronisers, signal, synchroniser, frequency, incoming, noise...
R&D Report 1993-03 : Coverage aspects of a Single Frequency Network designed for Digital Audio Broadcasting C.P. Bell, W.F. Williams Since the early 1960s, the VHF/FM pilot tone system has been used by broadcasters to supply high quality stereophonic programmes to listeners equipped with fixed receivers and modest gain directional antennas mounted externally at a height of about 10 metres above ground level. More recently, with the advent of improved radio receivers and digital technology...
Topics: frequency, bbc, antenna, required, network, propagation, protection, transmitters, guard,...
R&D Report 1993-01 : Digital sound: the selection of critical programme material and preparation of recordings for CCIR tests on low bit-rate codecs. N.H.C. Gilchrist A draft new recommendation on low bit-rate digital audio coding for broadcasting is in preparation within CCIR Study Group 10. As part of this work, subjective tests are being conducted to determine the preferred coding systems to be used in the various applications, and at which bit rates they should be used. The BBC has been...
Topics: codecs, audio, material, contribution, broadcasting, digital, recordings, codec, ccir, bbc,...
R&D Report 1993-10 : An introduction to digital modulation and OFDM techniques M.C.D. Maddocks This Report differs from most BBC Research Department Reports in that it does not contain details of a specific project undertaken at Kingswood Warren. While there has been a continuing development of aspects of digital modulation systems by BBC research engineers over many years, the purpose of this Report is to be tutorial. That is, digital transmission techniques need to be explained in a...
Topics: modulation, digital, signal, frequency, phase, multipath, symbol, systems, data, ofdm, simple...
R&D Report 1993-02 : Digital sound: subjective tests on commentary-quality codecs N.H.C. Gilchrist, A.J. Oxenham Subjective tests have been carried out on five commentary-quality audio codecs on behalf of CCIR Task Group 10/2. All codecs operated at a bit rate of 60 kbit/s per mono signal, and were tested in both mono and stereo configurations. Significant differences in performance were found. All codecs introduced some impairment on the most critical programme items.
Topics: mono, codecs, stereo, grades, audio, tests, bbc, codec, material, digital, khz sampling, department...
R&D Report 1993-07 Dynamic range control of audio signals by digital signal processing. N.H.C. Gilchrist
Topics: dynamic, audio, digital, compression, range, broadcasting, gain, signal, algorithm, processor,...
R&D Report 1992-03 : Optimum methods for the measurement of the absorption coefficients of materials. G.D. Plumb For the measurement of the absorption coefficients of materials in a reverberation room, the method currently used by the BBC differs from the ISO-Standard method, in the use of additional diffusion in the room and in the distribution of the sample. For the ISO-Standard method, adequate diffusion is achieved by using additional diffusing elements in the reverberation room,...
Topics: absorption, reverberation, absorbers, coefficients, diffusers, bbc, room, measurements,...
R&D Report 1992-05 : Helitrak: a helicopter-tracking receiver system for television outside broadcast links. C. Gandy Helicopters are used by BBC Television for certain live outside broadcasts which require an elevated platform for a camera or for a radio-link mid-point repeater. Video signals are communicated from the helicopter to the ground using microwave radio links, and the signals are received by a narrow-beamwidth dish antenna which must be kept pointing accurately towards the...
Topics: antenna, tracking, signal, signals, helicopter, received, bbc, receiver, positioner, system, ghz...
R&D Report 1992-11 : A modular wideband sound absorber G.D. Plumb The absorption coefficients were measured of various depths of RW2 grade Rockwool laid directly on the floor of the ISO-Standard reverberation room at BBC Research Department. The Rockwool was very effective as a wideband sound absorber. A new absorber was designed and tested, having the dimensions of existing BBC type A modular absorbers and containing RW2 Rockwool. The new absorber has a smoother absorption coefficient...
Topics: absorption, absorber, rockwool, infill, hardboard, plywood, modular, coefficient, absorbers, panel,...
R&D Report 1992-08 : Low-frequency room responses: Part 1 -- Background and qualitative considerations R. Walker The problems inherent in the reproduction of high-quality sound in relatively small rooms are discussed. Methods of predicting the inevitably uneven low-frequency response from source to listener or microphone are also discussed. It is concluded that, even with perfect prediction methods. there would still be some compromises which could only be resolved by making subjective...
Topics: frequency, frequencies, room, modes, acoustic, mode, response, sound, rooms, modal, low frequency,...
R&D Report 1992-07 : Effects of wind turbines on UHF television reception: field tests in Denmark, November 1991 D.T. Wright As a result of a planning application for a wind farm comprising 20 wind turbines at Tynewydd Farm, Gilfach Goch in Mid Glamorgan, it became necessary to produce a report discussing any detrimental effects the proposal might have on UHF television reception. In order to make that report as definitive as possible, it was decided to carry out field tests on the exact...
Topics: turbine, wind, turbines, antenna, measurements, transmitter, uhf, interference, blade, interfering,...
R&D Report 1992-10 : The design of a modular sound absorber for very low frequencies. J.A. Fletcher Studios and sound control rooms usually have their walls acoustically treated to control the reverberation time. in the BBC, this treatment often takes the form of modular absorbers of which there are a number of BBC designed types for sound absorption in different frequency bands. This report describes an investigation of the feasibility of a modular absorber for the 50-100 Hz frequency...
Topics: absorption, frequency, absorber, absorbers, bbc, helmholtz, reverberation, modular, measured, wave,...
R&D Report 1992-09 : Low-frequency room responses: Part 2 -- Calculation methods and experimental results. R. Walker The development of a relatively simple method for predicting low- frequency responses for near-rectangular rooms based on the summation of modal responses and their coupling coefficients for the source and receiver positions is outlined. Comparisons between calculated and measured responses show that many of the response features can be reproduced. The question of optimum...
Topics: room, frequency, loudspeaker, frequencies, loudspeakers, octave, measured, mode, modes, response,...
R&D Report 1992-02 : On minimising noise problems caused by passenger lifts in studio centres. C.D. Mathers A number of passenger lifts have been investigated as sources of noise and vibration. Typical measured results are presented, and a number of problems and solutions are discussed. Finally, some general recommendations are listed, indicating how noise nuisance may be avoided or remedied.
Topics: pump, lift, vibration, hydraulic, ram, slab, lifts, noise, measurements, mounts, pump vibration,...
R&D Report 1992-06 : An example of a phase-segregated enhanced PAL broadcasting system. M.G. Croll, J.O. Drewery, J.E.Easterbrook, R.Storey, G.A.Thomas An enhanced PAL system is described which is fully compatible with the terrestrial broadcast system B/G, having a 5 MHz bandwidth. Elimination of luminance/chrominance cross-effects is achieved using the principle of phase-segregation which also allows enhanced luminance resolution. The source picture has a 16:9 aspect ratio and appears on...
Topics: frequency, luminance, chrominance, pal, signal, phase, horizontal, vertical, letterbox, filter,...
R&D Report 1992-01 : UHF television reception: Ghost images from very large buildings. D.T. Wright, D.R. Cornell This report analyses the problem of ghost images to television picture reception caused by reflections from a very large building. For the particular case of the Canary Wharf Tower in London's Docklands, a basic theoretical analysis is compared with field measurements to gain some insight into the factors involved. Possible cures are also discussed.
Topics: ghost, canary, wharf, tower, reflection, signal, relative, antenna, beam, reflected, wharf tower,...
R&D Report 1992-04 : An investigation of the effects of boundary constraints on the sound insulations of lightweight, double leaf partitions. G.D. Plumb The sound insulation of a metal-framed, double leaf partition (measured in the Research Department Transmission Suite) was considerably lower when the two leaves of the partition were built into common, rather than independent, surrounding walls. The purpose of the work described in this Report was to investigate whether this shortfall in...
Topics: partition, surrounding, isolation, sound, built, perimeter, transmission, leaves, common,...
R&D Report 1992-12 : Experiments with the HIVITS HDTV contribution codec A.D.R. Cotton, N.D. Wells As more and more programmes are made in high definition television (HDTV) formats, so the need to provide complete production facilities will increase. An important part of television production is the ability to transmit very high quality television signals over long distances for programme contribution purposes. For example, this may be from an outside broadcast unit to a television studio...
Topics: buffer, coder, hdtv, codec, decoder, occupancy, regulation, stripe, transmission, quantiser,...
R&D Report 1992-13 : Measurement of display transfer characteristics using test pictures. A. Roberts There are three basic parameters which define the transfer characteristic of monitors: contrast, flare and gamma. Each of these can be measured, with varying degrees of accuracy, by a variety of methods. This Report attempts to clarify the definitions of the terms and to specify methods of measurement which give unique and repeatable results. Test pictures are described which permit...
Topics: measurement, flare, test, black, display, measurements, signal, contrast, displays, level, test...