WO2005109635A1

WO2005109635A1 - A method of audio reproduction at a receiver using an audio-equaliser

Info

Publication number: WO2005109635A1
Application number: PCT/GB2005/001829
Authority: WO
Inventors: Nick Banks
Original assignee: Radioscape Limited
Priority date: 2004-05-11
Filing date: 2005-05-11
Publication date: 2005-11-17
Also published as: GB0509607D0; GB2414123A; GB2414123B; GB0410454D0

Abstract

A method of audio reproduction at a receiver, comprising the step of the receiver automatically deploying an audio-equaliser parameter in dependence on programme type information received or processed by the receiver. Automatic selection of audio-equaliser parameters dependent on broadcast programme type information is a useful addition to an integrated or stand-alone radio receiver as it has the potential to enhance the listening experience of the user, and means that less interaction with the device is required, thus making the device easier and quicker to use. It finds particular application for in-car or in-vehicle receivers since a driver will rarely wish to manually select audio equaliser presets or manually alter audio equaliser configurations when driving; the advantages of an automatic method of doing so are considerable.

Description

A METHOD OF AUDIO REPRODUCTION AT A RECEIVER USING AN AUDIO-EQUALISER

FIELD OF THE INVENTION

This invention relates to a. method of audio reproduction at a receiver using an audio equaliser. The receiver may be a digital audio receiver such as a DAB or DRM receiver.

DESCRIPTION OF THE PRIOR ART

It is now common for personal and HiFi audio devices to possess an audio-equaliser, which amplifies or attenuates certain frequency bands of the selected audio source, thus allowing the user to customise the 'sound' of the audio source to cope with the acoustic characteristics of the listening environment, the limitations of the sound reproduction equipment (i.e. speakers) or the personal preferences of the listener. Typically, there are a number of preset equaliser parameters or configurations provided by the equipment . manufacturer that are suited to particular types of music (such as 'Rock', 'Jazz', 'Speech' and 'Classical'), and sometimes some user configurable parameters or settings so that the user can configure the equaliser to their exact requirements.

Currently, the selection of these audio-equaliser presets is done manually, so that if a user was to switch from a 'Classical' to a 'Jazz' music radio station on a device containing a radio tuner, they would also have to manually change the equaliser preset to the appropriate type.

^* In DAB (Digital Audio Broadcasting), DRM (Digital Radio Mondiale) and RDS-EON (FM) radio, program type information (e.g. News, Classical, Jazz etc.) is transmitted along with the selected audio service. This information can be displayed on the receiver, aiding an end-user when tuning to different stations. It can also be used to enable the end-user to navigate between radio stations of the same type (e.g. those broadcasting News). SUMMARY OF THE INVENTION

In a first aspect of the invention, there is a method of audio reproduction at a receiver, comprising the step of the receiver automatically deploying an audio-equaliser parameter in dependence on programme type information received or processed by the receiver. Hence, if the receiver tunes to a Jazz station (i.e. as defined by a Jazz programme type information), then it looks up the appropriate audio-equaliser parameter associated with jazz music and then automatically deploys it. This is far faster and more convenient that manual selection of the correct or optimal audio-equaliser parameter or setting.

If a number of audio-equaliser presets (equal to the number of distinct programme types) were provided or a suitable programme type to equaliser preset mapping was provided, then the appropriate audio-equaliser type could be selected automatically dependent on the received programme type; thus the user would not have to select the equaliser preset manually. Automatic selection of audio-equaliser parameters dependent on broadcast programme type information would be a useful addition to an integrated or stand-alone radio receiver as it has the potential to enhance the listening experience of the user, and means that less interaction with the device is required, thus making the device easier and quicker to use. It finds particular application for in-car or in-vehicle receivers since a driver will rarely wish to manually select audio equaliser presets or manually alter audio equaliser configurations when driving; the advantages of an automatic method of doing so are considerable.

In one implementation, the receiver includes several audio-equaliser parameters, each parameter being automatically deployed when a pre-defined programme type information is being received or processed by the receiver. Alternatively, the receiver may include audio-equaliser parameters, each capable of being assigned by an end-user to be automatically deployed when a different programme type information is being received or processed by the receiver. Hence, one audio-equaliser parameter could be labelled as 'loud' (it could boost the lower frequencies like a conventional 'loudness function). The end-user could program the receive so that it would deploy this particular audio-equaliser parameter or setting whenever a radio station with a 'Rock' programme type was being received or processed. An end-user could also define the details of the audio-equaliser parameter to be automatically deployed when a given programme type information is being received or processed by the receiver. For example, many audio receivers include a graphic equaliser set of controls to the audio equaliser; the end-user could then manually define a specific audio-equaliser parameter by setting the graphic equaliser controls in a certain position; he could then define that stations with a given programme type information would automatically deploy this specific specific audio-equaliser parameter. The equaliser could be an analog equaliser or a digital equaliser. The receiver may also include an over-ride function that enables an end-user to disable the automatic deployment of an audio equaliser parameter and to instead manually set the audio equaliser parameter.

In a preferred implementation, the structure of an audio codec in the receiver provides equalisation directly by adjusting the coefficients/scale factors of the individual frequencies/ sub-bands synthesised in the codec. -For example, the scale factors are multiplied by pre-determined amounts to generate audio equalisation appropriate to the programme type. The codec could be a MPEG-1 Layer 2 or Layer 3 codec.

The receiver can be a digital audio broadcasting (DAB) receiver and programme type information is then in the Fast Information Group in the Fast Information Channel. Another implementation is a Digital Radio Mondiale (DRM) receiver and the programme type information is then contained within the Service Parameters of the Fast Access Channel (FAC). The programme type information could also be contained in a file.

In a second aspect, there is a receiver adapted to reproduce audio, in which the receiver is adapted to automatically deploy an audio-equaliser parameter in dependence on programme type information received or processed by the receiver. The receiver could be a DAB, DRM, DNB or DNB-H receiver. In a preferred implementation, the receiver is an in-car receiver. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to the accompanying drawings, in which:

Figure 1 is a block diagram of a receiver with an audio-equaliser implementation in accordance with the present invention;

Figure 2 is a block diagram of a receiver with an audio-equaliser implementation in accordance with the present invention in which equalisation is applied by adjusting scale factors in an audio decoder.

DETAILED DESCRIPTION

The following description specifically uses the Digital Audio Broadcasting (DAB) system as defined by Eureka-147 and described in the ETSI standards document ETS 300 401. Note however that the method generally applies to any system which provides a Programme Type (PTy) information field (or anything functionally equivalent or similar). In the case of DAB,, this information is provided in the Fast Information Channel (FIC) and is essentially a signal. For other systems it may be contained in a file header or even an associated descriptor or help file.

An example implementation of the invention is shown in Figure 1 for the DAB case. The off-the-air broadcast signal is received by the Receiver and Demodulator (1) which separates and outputs various demodulated data. Within that data the Main Service Channel (MSC) contains the 'content'. The 'content' will usually consist of music or speech but may also contain data services. The required sub-channel in the MSC is selected by the Control and User Interface functionality (8) and decoded according to the channel coding plan that has been applied (2). That channel coding plan is signalled via the FIC and decoded using FIC decoder unit (6). Once the sub-channel data has been decoded, in the case of audio (e.g. music or speech) it is passed to the audio decoder (3) where it is typically converted to PCM format ready for application to the audio output (5). Note that other output forms exist including digital formats such as SPDIF. In the usual case the audio signal will pass directly from the audio decoder (3) to the output (5). In more advanced systems the audio may be passed to the output via an audio equaliser function (4). Previously, this function has been controlled manually, where the user will select an equaliser setting appropriate to the content and the listening environment.

The programme type information allows the receiver to have knowledge of the type of content that is being received, e.g. Rock, Jazz, sports commentary etc.. And with the present invention, this is used for the automatic selection of the audio equaliser settings. The Programme Type (PTy) information is extracted from the Information Channel (in the case of DAB from the Fast Information Group (FIG 0/17) in the FIC channel) and decoded to determine the programme type in the FIG extractor/interpreter (7) in Figure 1. The code received will correspond to a pre-assigned audio type. The equaliser setting that has been associated with that programme type (e.g. in a simple look up table) is then activated in the equaliser. In this way, the user can have the audio of the received signal adjusted to suit their own requirements. For a DRM implementation, the Programme Type information is contained in the Service Parameters of the Fast Access Channel (FAC). Hence, if the user tunes to a jazz music station broadcasting a 'jazz' Programme Type information, that PTy information is automatically correlated in the receiver to a preset audio equalisation configuration, which is then automatically deployed. Likewise, if the user tunes away from the jazz station to a classical station with a 'classical' PTy tag, then the receiver automatically uses that tag to determine the appropriate audio equalisation parameters to deploy and then automatically proceeds to deploy them.

The present invention is not limited to receivers that are purely audio receivers; it can for example be deployed in receivers that receive video. For DNB receiver (e.g. DNB-H), it is possible for Programme Type information to be specified in the Service Information.

Referring again now to the drawings, in Figure 1 the equaliser is applied as an audio equaliser, using either analog or digital implementation. Typically the equaliser will be applied as the standard Bass/Treble implementation or a 'Graphic Equaliser' where the level of a number of sub-bands, or frequencies, can be controlled. In both cases, the level of the audio signal within the selected frequency ranges (e.g. treble may be the audio signal above 2 kHz, while for a Graphic Equaliser a 10 band implementation would typically have a sub-band centred at 1kHz) can be adjusted, for example, by as much as plus or minus lOdB or more.

Another implementation is to apply the required signal adjustments directly within the audio decoder itself. This is particularly the case for audio codecs which encode the audio using parametric means as is the case, for example, in MPEG-1. The audio codec generally used in DAB is the MPEG-1 Layer 2 codec, also called MP2. In this case, the audio is coded based on sub-band filtering according to a psychoacoustic model. Each sub-band has an associated scale factor which represents the level of that sub-band within the overall signal. In the audio decoder the scale factors are applied to synthesised signals for each sub-band. As shown in Figure 2 the equalisation can be directly applied at this stage by simply adjusting the scale factors. Essentially this simply requires the multiplication of the scale-factors and the preset equaliser coefficients (e.g. as read from a simple Look Up Table) at the time of application and hence is a very efficient method of implementation.

The same method may also be used for MP3 (MPEG-1 Layer 3) encoded signals as well as other audio codecs which use a sub-band encoding methodology. We note that the implementation of the equaliser is strictly dependent on the receiver only and requires no modification of any transmission equipment. It is simply sufficient that the broadcaster includes the programme type information in the transmission. The receiver manufacturer is then at liberty to implement any number of styles of equaliser which may have different sub-band selectivity or simply base/treble control.

Claims

1. A method of audio reproduction at a receiver, comprising the step of the receiver automatically deploying an audio-equaliser parameter in dependence on programme type information received or processed by the receiver.

2. The method of Claim 1 in which the receiver includes several audio-equaliser parameters, and each is automatically deployed when a pre-defined programme type information is being received or processed by the receiver.

3. The method of Claim 1 in which the receiver includes several audio-equaliser parameters, each capable of being assigned by an end-user to be automatically deployed when a different programme type information is being received or processed by the receiver.

4. The method of Claim 1 in which an end-user defines the details of the audio- equaliser parameter to be automatically deployed when a given programme type information is being received or processed by the receiver.

5. The method of Claim 1 in which the equaliser is an analog equaliser.

6. The method of Claim 1 in which the equaliser is a digital equaliser.

7. The method of Claim 1 in which the receiver includes an over-ride function that enables an end-user to disable the automatic deployment of an audio-equaliser parameter and to instead manually set the audio equaliser parameter.

8. The method of Claim 1 in which the structure of an audio codec in the receiver provides equalisation directly by adjusting the coefficients/scale factors of the individual frequencies/sub-bands synthesised in the codec.

9. The method of Claim 8 in which the scale factors are multiplied by predetermined amounts to generate audio equalisation appropriate to the programme type.

10. The method of Claim 8 in which the codec is a MPEG-1 Layer 2 or Layer 3 codec.

11. The method of Claim 1 in which the receiver is a digital audio broadcasting (DAB) receiver and programme type information is in the Fast Information Group in the

Fast Information Channel.

12. The method of Claim 1 in which the receiver is a Digital Radio Mondiale (DRM) receiver and programme type information is contained within the Service Parameters of the Fast Access Channel (FAC).

13. The method of Claim 1 in which the programme type information is contained in a file.

14. A receiver adapted to reproduce audio, in which the receiver is adapted to automatically deploy an audio-equaliser parameter in dependence on programme type information received or processed by the receiver.

15. The receiver of Claim 14, being a DAB, DRM, DNB or DVB-H receiver.

16. The receiver of Claim 15, being an in-car receiver.