By Topic

Digital Audio Signal Processing, IEE Colloquium on

Date 22 May 1991

Filter Results

Displaying Results 1 - 10 of 10
  • On the re-allocation of processing resources for digital audio signal processing

    Page(s): 7/1 - 7/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    When implemented digitally, large-scale audio processing systems require the realisation of highly parallel architectures. Task scheduling strategies are necessary to distribute the processing algorithms required-termed the taskforce-across such architectures. The results obtained show that good-quality solutions can be expected from simple heuristic methods with minimum scheduling overhead. More advanced heuristic policies demonstrate particular promise for fast near-optimal re-allocation of processing resources in real-time audio processing applications View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design limitations for digital audio power amplification

    Page(s): 4/1 - 4/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    The factors which limit linearity and resolution in digital to analogue conversion (DAC) based on pulse width modulation (PWM) and oversampled noise shaping (ONS) are compared using signal to noise ratio (SNR) and total harmonic distortion (THD) figures. Solutions to each of these factors are suggested, with an indication of the level of effectiveness that can be expected in a practical PWM/ONS digital power amplifier. Results imply that using current technology, 146 dB SNR and THD can be achieved with this type of audio power amplifier View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High quality digital audio

    Page(s): 111 - 112
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    Suggests that in digital-audio systems aspiring to the description `high-quality', an area of major importance is its accuracy in handling low-level signals. To some extent this focus reflects the author's direct experience designing and using digital audio components. The mechanisms of low-level distortions, both static and dynamic have been examined, as has the behaviour of some converter and DSP combinations. To assess the significance of noise and distortion products, auditory-band filtering was introduced, and the error of using 1/3oct filtering was examined. Setting typical replay levels for the system allows us estimation of the detectability of noise and other errors in the system. The author has proposed determining a quality measure based on the difference between the spectra TPD, triangular probability distributions, modulation noise and digital silence-where for a perfect chain all three curves would overlay. This raises some questions on the wisdom of using noise-shaped dither in real systems View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design and performance of a noise shaping, pulse width modulated, digital to analogue converter

    Page(s): 2/1 - 2/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    Describes the implementation of an audio DAC which is based on oversampled, noise shaped pulse width modulation. The basic principles of oversampled noise shaping (ONS) and pulse width modulation (PWM) are outlined, with particular reference to how ONS is used to relax the design specifications of the PWM circuit. The DAC has been tested by measuring its response to digitally generated tones from a commercial test disc via an 8x oversampling CD player. The results of these tests are shown to be in close agreement with previous theoretical and computer simulation results. Furthermore, ONS PWM is shown to be suitable for the direct conversion of digital audio data into analogue power using a fast MOSFET power switch, subject to switching efficiency considerations highlighted by Hiorns, et al. (ibid., p.4/4-4) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A methodological critique of local room equalization techniques

    Page(s): 6/1 - 6/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    A local room equalization scheme for an audio system is desired where the equalization is valid over an area large enough to allow for head movements and ideally for other listeners situated nearby. The authors aim to provide some introductory insight into the size of this area, termed region of equalization (ROE), which depends on many factors-room geometry, boundary treatments, speaker/listener positions, etc. The work forms part of a more detailed study currently in progress of the room-loudspeaker interface and its effective control View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • IEE Colloquium on `Digital Audio Signal Processing' (Digest No.107)

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (20 KB)  

    The following topics were dealt with: high quality digital audio; D/A conversion; power amplifiers; DSP technology and marketing; local room equalisation techniques; digital audio in TV studios; and multiprocessor architectures for audio DSP View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A scalable hybrid multiprocessor for real-time digital audio signal processing

    Page(s): 9/1 - 9/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    The real-time performance requirements of large scale digital audio processing systems demand the use of a computation engine rated in thousands of MIPs. Currently available processors are not capable of operating at these speeds, and so multiprocessor architectures must be constructed in order to implement such systems. The choice of processor, communication scheme and interconnection topology are all important design considerations if an efficient multiprocessor is to be realised. The authors relate these three design choices to the design of a scalable hybrid digital signal multiprocessor offering a very efficient inter-processor communication scheme that allows processor idle time to be reduced to zero View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Improved sampling process for a digital, pulse-width modulated, class D power amplifier

    Page(s): 3/1 - 3/5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    A pulse-width modulation sampling process has been derived which is suitable for implementation in an entirely digital system, but has a performance comparable with that of natural sampling. The new process introduces negligible distortion to audio bandwidth signals at pulse carrier frequencies of 176 kHz or above. As a result it should be possible to realise a high efficiency, high performance class D power amplifier View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sample rate conversion and bit rate reduction in the studio

    Page(s): 8/1 - 8/3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    The standardisation of audio interfaces has enabled a proliferation of digital audio equipment to be used and interconnected to the great benefit of broadcasters and the services they provide. However, it has also introduced additional requirements for sample rate conversion (integer ratio conversion and variable rate conversion) and bit rate reduction processes at many interfaces in the signal routes within the TV studio View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Digital signal processing: technology and marketing for audio systems

    Page(s): 5/1 - 5/6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    Compact disc (CD) and digital audio tape (DAT) formats are now widely accepted as being a very reliable and high quality means of reproducing music. With these new systems has come considerable new terminology and technology. A visit to any high street store will confirm that the marketing and advertising strategies for these systems discusses the attributes of digital filters, 4X's oversampling, analogue to digital conversion, bit-stream conversion, anti-aliasing filters and so on. Graphics equalisers can be purchased that allow very precise digital filter control over the frequency range 100 Hz to 20 KHz. Top of the range amplifiers include displays that perform real time spectrum analysis. The author looks at the way in which digital signal processing is being brought to the general public's attention by digital audio systems and discusses the state of the art capabilities of DSP in audio systems View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.