1. Technical Field
This invention relates to digital audio processing, for example for use in audio reproduction systems such as hi-fi systems.
2. Description of Related Art
Hi-fi systems can be built up by a user from individually boxed components such as radio tuners, cassette player/recorders, compact disc (CD) players, amplifiers and loudspeakers. The components are connected together so that audio signals can be passed between them in analogue form, from a source component to an amplifier and then to loudspeakers. Systems of this sort are generally expensive, because of the need for separate enclosures, power supplies and circuitry for each component.
In an integrated hi-fi system all of the components except often the loudspeakers are integrated in a single enclosure. However, within that enclosure there is generally little integration at a circuit level between the components, other than the sharing of a power supply. An integrated hi-fi system typically comprises a number of audio source devices, such as radio tuners, cassette player/recorders and compact disc (CD) players, each of which has dedicated electronic circuitry for performing processing associated with its particular functions. For example, a typical radio tuner will have circuitry for demodulating, decoding and equalising received signals, a cassette deck will have circuitry for equalising data recovered from cassette tape in accordance with the type of the tape, and a CD player will have circuitry for error correction and detection and control of tracking and focus errors. From each of these sections of the system analogue audio signals are produced. These signals are fed to common circuitry for allowing features of the signal such as volume and tone to be controlled in the analogue domain, resulting in an analogue output signal that is fed to amplifiers and loudspeakers.
Such integrated systems are complex to manufacture. The circuitry to support the audio devices, in addition to user interface devices such as switch matrices, infra-red remote controllers and displays, involves many separate components, which have to be mounted on circuit boards in such a way that they can be fitted into a single enclosure. As a result, the component and manufacturing costs of such systems are relatively expensive; and if there is a fault, finding which of the many components is damaged can require time consuming and technically demanding testing.