WO2006134516A1

WO2006134516A1 - Receiving radio broadcasts

Info

Publication number: WO2006134516A1
Application number: PCT/IB2006/051807
Authority: WO
Inventors: Kai Eck
Original assignee: Koninklijke Philips Electronics N.V.; Philips Intellectual Property & Standards Gmbh
Priority date: 2005-06-17
Filing date: 2006-06-07
Publication date: 2006-12-21

Abstract

A method for supplying audio signals to a user includes receiving a radio frequency broadcast signal, demodulating the received radio frequency signal to provide an audio signal, and extracting a parameter value from the audio signal. The extracted parameter value is compared with stored parameter values relating to stored audio signals, and a stored audio signal in dependence upon the comparison of the received parameter value and the stored parameter value. The received audio signal or the stored audio signal is output in dependence upon the quality of the received audio signal. Such a technique enables high quality audio reproduction to be maintained even if the received radio signal suffers degradation.

Description

Receiving radio broadcasts

The present invention relates to receiving radio broadcasts, and in particular to receiving frequency modulated (FM) radio broadcasts in vehicles.

Receiving broadcasted music on FM (frequency modulated) radio whilst moving, for example in a vehicle, is often affected by distortions that are caused by the increasing distance of the vehicle and the transmitting station or by shadow effects of the landscape. In such situations, the transmission quality is good enough to recognize the track played but often not good enough to really enjoy listening to the music. One previously-considered solution is to program the receiver to search automatically for other frequencies broadcasting the same channel and switch to that frequency if the reception quality falls below a certain threshold. This technique obviously fails if the channel is broadcasted on only one frequency. Also, advanced methods for error removal have been proposed that try to reduce the influence of the distortions on the perceived quality. Such techniques generally are able to reduce the influence of low level distortions (noise etc.) but tend to fail when dealing with strong distortions (like multi-second signal losses).

Such previously considered techniques are complex and can be difficult to implement, particular in vehicle-based systems. It is therefore an object of the present invention to provide an improved FM radio receiver.

Embodiments of the present invention can enable perfect music quality to be provided in automotive and mobile applications even under conditions where the music would be barely recognizable when it is played based solely on a received radio signal.

According to a first aspect of the present invention, there is provided a method for supplying audio signals to a user, the method comprising receiving a radio frequency broadcast signal, demodulating the received radio frequency signal to provide an audio signal, extracting a parameter value from the audio signal, comparing the extracted parameter value with stored parameter values relating to stored audio signals, retrieving a stored audio signal in dependence upon the comparison of the received parameter value and the stored parameter value, and outputting the received audio signal or the retrieved stored audio signal in dependence upon the quality of the received audio signal.

According to a second aspect of the present invention, there is provided a radio receiver comprising a receiver unit (10) operable to receive a radio frequency broadcast signal, a demodulator (10) operable to demodulate a received radio frequency signal to produce a received audio signal (m), an extractor unit (14) operable to extract a parameter value (f) from such a received audio signal (m) to produce an extracted parameter value, a storage device (18) operable to store a plurality of stored audio tracks (m') and respective related stored parameter values(f ), a comparison unit (20) operable to compare an extracted parameter value (f) with stored parameter values (f ) to produce a comparison signal, a track retrieval unit (22) operable to retrieve a stored audio track from the storage device (18) in dependence upon a comparison signal received from the comparison unit (20), and an output unit (16, 24) operable to output the received audio signal (m) or the retrieved stored audio signal (m') in dependence upon a quality level of the received audio signal.

Such a method and receiver enable the maintenance of high quality audio output to a user, even if the received radio broadcast signal deteriorates in quality.

In one embodiment, the received audio signal is output when the quality thereof is above a first predetermined level. In another embodiment, the stored audio signal is output when the quality of the received audio signal is below a second predetermined level.

The audio signal may include first and second audio tracks, in which case at least one parameter value is extracted and compared for the first audio track, and a stored first audio track corresponding to the first audio track is retrieved, and the stored first audio track and the second audio track are output in combination.

Such a technique enables a music track, for example, to be played at high quality, whilst maintaining an overlaid voice track, such as a DJ. According to a third aspect of the present invention there is provided a radio broadcast system comprising a radio transmitter operable to transmit a radio frequency broadcast signal, and a radio receiver in accordance with the second aspect of the invention. Fig. 1 illustrates FM radio reception;

Fig. 2 illustrates a system embodying one aspect of the present invention; and Fig. 3 illustrates a method embodying another aspect of the present invention.

Fig. 1 illustrates FM radio reception in a vehicle. A FM radio frequency signal 1 is broadcast from a transmitter 3 and is received at a vehicle 5, in known manner. As described above, the signal received by the vehicle 5 can vary in dependence upon geographic and environmental conditions. For example, the signal can degrade when the vehicle 5 passes through a highly wooded area or an urban area. Embodiments of the present invention, therefore, aim to reduce the effect of these quality variations on the radio program listened to by the user of the vehicle.

Fig. 2 illustrates a system embodying one aspect of the present invention. The system shown in Fig. 2 comprises an FM receiver 10, which includes an antenna for receiving FM broadcasts from the transmitter (of Fig. 1). The FM receiver 10 operates in conventional manner and is operable to demodulate the received radio signal and to supply a program track, for example a music track m, to an output loudspeaker 24 of the system, via a combiner 16. Operation of the combiner 16 will be described in more detail below. In the description, a music track m is described. However, it will be readily appreciated that the present invention can be applied to any audio signal received by the FM receiver 10.

The system also includes a storage device 18, which stores music tracks and associated data, as described below. The storage unit 18 receives music tracks and data to be stored from a storage manager unit 12. The music track m is supplied to the storage manager unit 12 for storing in the storage device 18. The storage manager unit 12 operates to control writing of music tracks to the storage device 18.

In an embodiment of the present invention, the FM receiver 10 supplies the music track m to a feature extractor 14 which operates to extract a "feature vector"/from the music track m. The feature vector/is supplied to a comparison unit 20. The storage device 18 stores feature vectors/' for each of the stored music tracks m ', and the stored feature vectors /' are supplied to the comparison unit 20. A track decoder 22 receives track information from the comparison unit 20, and supplies that track information to the storage device 18 for retrieval of the stored track m ' corresponding to the received track m.

The operation of the system shown in Figure 2 will be described with reference to the flow chart of Figure 3. As the FM radio frequency broadcast is received (step A) the music track is supplied from the FM receiver 10 to the combiner 16 to the feature extractor 14 and to the storage manager 12. The feature extractor 14 extracts the feature vector/relating to the received music track m (step B) and supplies the feature vector/ to the comparison unit 20. The storage unit 18 supplies stored feature vectors/' to the comparison unit 20 for comparison with the received feature vector/ The comparison unit compares (step C) these two feature vectors, and determines whether the storage unit 18 stores the music track m received by the FM receiver 10. If the comparison unit determines that the received and stored feature vectors/and/' are equivalent, then it supplies a signal to the track decoder 22 which in turn supplies a track indicator i to the storage unit 18. The storage unit 18 outputs a stored music track m ' in response to receipt of this track information, to the track decoder 22, which passes the stored music track m ' to the combiner 16. The combiner 16 selects or combines the received music track m with the stored music track m ' for supply to the output loudspeaker 24.

In a situation when the FM receiver 10 is receiving high quality FM signals, and that therefore the quality of the music track m is of sufficient level to be enjoyable, the combiner 16 simply outputs the received music track m to the loudspeaker 24. Optionally, this high quality music track can be recorded, if it has not already been recorded, in the storage unit 18 under the control of the storage manager 12.

However, as the quality of the FM reception drops, the quality of the music track m accordingly drops. In that case, the combiner 16 switches to output the alternative music track m ' received from the storage unit 18. This provides the listener with a high quality version of the music track that is currently being supplied by the FM receiver at low quality. As the quality of the FM reception returns, then the music track being played through the loudspeaker 24 can be switched back to the original music track m. It is common in FM radio transmissions for speech and music to overlap.

Accordingly, in another embodiment of the present invention the combiner 16 operates to filter out the speech signal from the original music track m and combines that with the stored music track m ' in order to provide a high quality music, without loss of the associated speech signals. This is done by first subtracting the stored, high-quality music track from the received music track. The result contains only the speech which is distorted by the transmission distortions. This signal is filtered using speech signal restoration techniques known to those working in this field. Afterwards, the restored speech signal is again added to the stored music signal and is provided to the listener. Accordingly, it can be seen that the embodiments of the present invention provide a system and technique in which high quality music signals can be relayed to users of vehicles, whilst maintaining the reception of an FM radio broadcast. It will be appreciated that, although the present invention has been described with reference to music tracks, it is applicable to any recorded audio signal.

In addition, embodiments of the present invention are also able to deal with temporally distorted signals. If, for example, a DJ regularly talks while the song is still playing, the undistorted song can be reconstructed from multiple broadcastings of the distorted song by combining the undistorted temporal samples. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parentheses shall not be construed as limiting the claims. The words "comprising" and "comprises", and the like, do not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer, if appropriate. In a claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. A method for supplying audio signals to a user, the method comprising: receiving a radio frequency broadcast signal; demodulating the received radio frequency signal to provide an audio signal; extracting a parameter value from the audio signal; comparing the extracted parameter value with stored parameter values relating to stored audio signals; retrieving a stored audio signal in dependence upon the comparison of the received parameter value and the stored parameter value; and outputting the received audio signal or the retrieved stored audio signal in dependence upon the quality of the received audio signal.

2. A method as claimed in claim 1, wherein the received audio signal is output when the quality thereof is above a first predetermined level.

3. A method as claimed in claim 1 or 2, wherein the stored audio signal is output when the quality of the received audio signal is below a second predetermined level.

4. A method as claimed in claim 1, 2 or 3, wherein the audio signal includes first and second audio tracks, and the method comprises extracting and comparing at least one parameter value for the first audio track, retrieving a stored first audio track corresponding to the first audio track, and outputting the stored first audio track and the second audio track in combination.

5. A radio receiver comprising: a receiver unit (10) operable to receive a radio frequency broadcast signal; a demodulator (10) operable to demodulate a received radio frequency signal to produce a received audio signal (m) ; an extractor unit (14) operable to extract a parameter value (f) from such a received audio signal (m) to produce an extracted parameter value; a storage device (18) operable to store a plurality of stored audio tracks (m') and respective related stored parameter values(f ); a comparison unit (20) operable to compare an extracted parameter value (f) with stored parameter values (f ) to produce a comparison signal; a track retrieval unit (22) operable to retrieve a stored audio track from the storage device (18) in dependence upon a comparison signal received from the comparison unit (20); and an output unit (16, 24) operable to output the received audio signal (m) or the retrieved audio signal (m') in dependence upon a quality level of the received audio signal.

6. A receiver as claimed in claim 5, wherein the output unit (16,24) is operable to output the received audio signal if the quality level of the received audio signal is above a first predetermined level.

7. A receiver as claimed in claim 5 or 6, wherein the output unit (16,24) is operable to output the stored audio signal if the quality level of the received audio signal is below a second predetermined level.

8. A receiver as claimed in claim 5, 6 or 7, wherein the received audio signal includes first and second audio tracks, and the extractor unit (14), comparison unit (20) and track retrieval unit (22) are operable to process the first audio track, and the output unit (16, 24) is operable to combine and output a retrieved audio signal corresponding to the first audio signal and the second audio signal.

9. A radio broadcast system comprising a radio transmitter operable to transmit a radio frequency broadcast signal, and a radio receiver as claimed in any one of claims 5 to 8.