Audio Source Selection

Abstract

A processor (4) receives (I1,I2) a first audio and/or video input signal (A1, V1), and a second audio and/or video input signal (Λ2, V2, Λ1b, Λ1c, Λ3, A5). A comparator (41) compares the fist audio or video input signal (A1, V1) and the second audio or video input signal (A2, V2; A1b, A1c, A3, A5), respectively, to detect a match between the first audio signal (A1) and the second audio signal (A2) or the first video signal (V1) and the second video signal (V2). A selector (42) supplies a selected signal ΛS) which is the second audio or video input signal (A2, V2) if the match is detected or the first audio or video input signal (A1, V1) otherwise.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a block diagram of a system which comprises a display apparatus, an audio-video source and an audio processor,

FIG. 2 shows a more detailed block diagram of a system which comprises an audio-video source, an audio source, a display apparatus, and a receiver which comprises the audio processor,

FIG. 3 shows a detailed block diagram of an embodiment of the audio processor, and

FIG. 4 shows a detailed block diagram of another embodiment of the audio processor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a block diagram of a system which comprises a display apparatus, an audio-video source (further referred to as AV-source) and an audio processor. The AV-source 1 supplies a first audio signal Ala which is accompanied by a video signal V1a to the display apparatus 2. The display apparatus 2 comprises a selector (not shown in FIG. 1, see FIG. 2) to select which signal should be displayed on its display. The selector is in a position to display the video signal V1a and to supply the audio signal A1a as the audio signal A1 and/or the video signal V1 to the input I1 of the audio processor 4. The audio signal A1 and the video signal V1 resemble the audio signal A1a and the video signal V1a, respectively, very much. These signals only have to pass the selector and may be amplified/buffered. Also, some pre-processing as noise suppression may be performed on the audio signal A1a and the video signal V1a. The audio signal Al and the video signal V1 belong to the same information and thus are related. For example, the AV-source 1 comprises a DVD player which supplies an analog stereo signal as the audio signal A1 and component video as the video signal V1. The display apparatus 2 may be a television apparatus, a computer monitor, a beamer, or any other display apparatus suitable to display images to which audio is associated. The first audio signal A1a is transported over an interface cable to the display apparatus 2. This interface cable may be a standard scart cable which also transports the video signal V1a from the AV-source 1 to the display apparatus 2.

The audio processor 4 comprises a further input I2 to receive a second audio signal A2 and/or a second video signal V2 which also originate(s) from the AV-source 1. For example, the second audio signal A2 is a digital stereo or multi-channel audio signal. The audio signal A2 may alternatively be an analog or digital multi-channel audio signal. The audio signal A2 may be transported by a single digital interface cable or by a plurality of analog interface cables. The video signal V2 may be composite video.

The audio processor 4 comprises a comparator 41, a controller 40 and a selector 42. The comparator 41 receives the (first) audio signal A1 and the (second) audio signal A2 and supplies a comparison signal CS. The comparison signal CS indicates whether the comparator 41 detects a match between the first audio signal A1 and the second audio signal A2. The comparator 41 may use well known cross-correlation or fingerprinting techniques to determine whether the match exists. An example of a suitable cross-correlation technique is disclosed in “Theory and application of Digital Signal Processing”, L. R. Rabiner and B. Gold, Prentice Hall, 1975. An example of a suitable fingerprinting technique is disclosed in U.S. Pat. No. 6,453,252. The fingerprint of an audio signal is generated based on the energy content in frequency sub-bands. Processing techniques assure a robust identification fingerprint useful to identify signals which are altered after the fingerprint was generated. The fingerprint is compared to a database to identify the audio signal. A match is not intended to mean that the signals compared should be identical, or that the cross-correlation should be 100%, or that the fingerprints should be identical. It may suffice if the signals or the fingerprints are almost identical, or that the cross-correlation is higher than a predetermined level.

The controller 40 receives the comparison signal CS and optionally the priority information PI to supply the select signal SE. The priority information PI indicates the priority of different audio signals. For example, the priority information PI may indicate that a multi-channel audio signal has a higher priority than a stereo signal, and that a digital audio signal has a higher priority than an analog audio signal. The priority information PI may be stored in a memory, or may be determined based on the origin of the signal and thus may be dependent on the input on which the signal is present. Alternatively, a signal with a higher signal to noise ratio may have a higher priority than a signal with a lower signal to noise ratio.

The selector 42 receives the first audio input signal A1, the second audio input signal A2, and the select signal SE to supply a selected audio signal AS to an output O. If the comparison signal CS indicates that the second audio signal A2 matches the first audio signal A1, and the priority information PI indicates that the priority of the second audio signal A2 is higher than that of the first audio signal A1, the select signal SE controls the selector 42 to select the second audio signal A2 as the selected audio signal AS. In all other situations, the select signal SE controls the selector 42 to select the first audio signal A1 as the selected audio signal AS.

By way of example, the AV-source 1 is a DVD player, the first audio signal Al is an analog stereo audio signal, and the second audio signal A2 is a digital multi-channel audio signal. The priority of the digital multi-channel audio signal prevails above the priority of the analog stereo audio signal. Because both the first audio signal A1 and the second audio signal A2 originate from the same AV-source 1, they are correlated and thus the comparator 41 will detect a match. Because both a match is detected and the priority of the second audio signal A2 is the highest, the second audio signal A2 will be automatically selected. If no priority information is used, the second audio signal A2 is selected if it matches the first audio signal A1. Thus, the user does not have to take any action. As long as the audio processor 4 receives the first audio signal A1, it is able to detect whether the second audio signal A2 is matching, and knowing the priorities, the highest priority audio signal will be selected. Thus, if the second (multi-channel) audio signal A2 matches the first (stereo) audio signal A1, this better second audio signal A2 will be selected and thus be heard. If the second audio signal A2 does not match the first audio signal A1, this first audio signal A1 is selected. No match is detected, for example, if the user did not attach a cable between the AV-source 1 and the input I2 of the audio processor 4, or if the user attached a cable to the input I2 which provides a sound signal from a source different than the AV-source 1.

In the same manner, instead of comparing audio signals, also the video signals V1 and V2 may be compared to control the selection.

FIG. 2 shows a more detailed block diagram of a system which comprises an AV-source, an audio source, a display apparatus, and a receiver which comprises the audio processor. The system now comprises an AV-source 1, an audio source 6, a data source 8, a display apparatus 2 and an audio-video receiver 3 (further referred to as AV-receiver or receiver).

The AV-source 1 may be a DVD player which supplies an analog stereo audio signal A1a and a component video signal V1a to the display apparatus 2. The AV-source supplies an analog multi-channel audio signal A1b, and a digital stereo or multi-channel audio signal A1c and optionally a composite (or S) video signal V2 to inputs I2r, I3r and I4r of the receiver 3, respectively. Usually, either the digital multi-channel audio signal or the digital stereo signal is present on the same interface cable connected between the DVD player 1 and the receiver 3. The video signal V1a may be component video signal (R, G, B, not shown) and the video signal V2 may be a composite video signal. Instead of the DVD player 1 any other AV-source which supplies different sound formats and/or video formats in parallel can be used. The audio source 6 supplies a multi-channel analog or digital signal A3 to the input I5 of the receiver 3. The remote content source 8 supplies information A5 to the input I6 of the receiver 3. This information A5 may be a digital data stream. The remote content source 8 may be, for example, an internet server.

The display apparatus 2, which in this embodiment is a TV comprises a tuner 20, a selector 21, a sound processor 22, a video processor 23, two loudspeakers 25 and 26, and a display 24. The tuner 20 receives television programs and supplies the television audio signal At and the television video signal Vt. The selector 21 selects the television audio signal At and the television video signal Vt from the tuner 20, or the analog stereo audio signal A1a and the video signal V1a from the AV-source 1. The selected audio signal Ad is supplied to the sound processor 22 which supplies loudspeaker signals LS1 and LS2 to the loudspeakers 25 and 26. The selected video signal Vd is supplied to the video processor 23 which supplies drive signals DS to the display 24. The selected audio and video signals are also supplied to the outputs TO1 and TO2 of the display apparatus 2 as the output audio signal A1 and the output video signal V1, respectively. In FIG. 2, the selector 21 selects the analog stereo audio signal A1a and the video signal V1a from the AV-source 1. The output video signal V1 is related or identical to the video signal V1a, the output audio signal A1 is related or identical to the audio signal A1a. With related to is meant that the signals mentioned are processed but such that they have a very high resemblance, for example, only the amplitudes are different, or a noise reduction algorithm is performed. The output video signal V1 and the output audio signal A1 are supplied to the input I1r of the receiver 3 via a standard interface cable, for example, via a scart cable.

The receiver 3 comprises the audio processor 4 and a decoder/output amplifier 5. The audio processor 4 receives the analog stereo output audio signal A1 via the input I1r, the analog multi-channel audio signal A1b via the inputs I2r, the digital stereo or multi-channel audio signal A1c via the input I3r, the multi-channel analog or digital signal A3 via the input I5r, and the audio signal A5 which originates from a distant content source 8 via the input I6r. The distant content source 8 may be coupled via wire or wireless (for example, WLAN), for example, by phone or by internet.

The audio processor 4 comprises the comparator 41, the controller 40 and the selector 42 shown in FIG. 1 (not shown in FIG. 2). The comparator 41 checks each (or a relevant sub-group) of input audio signals A1b, A1c, A3, A5 whether there is a match. If at least one match is found, the priority of the matching input audio signal(s) is checked and the matching input audio signal with the highest priority is selected to be supplied to the decoder/output amplifiers 5. The selected audio signal AS may be a digital signal which is first decoded 5 before it is amplified by output amplifiers 5. The selected audio signal AS may be an analog audio signal which only needs to be amplified by the amplifiers 5. It is also possible that all digital audio signals are first decoded into analog audio signals before the selection is made. Now the decoder/amplifiers 5 only comprise amplifiers. FIG. 2 shows, by way of example only, a 5.1 channel AV-receiver 3 which has 6 outputs Q1 to Q6, respectively, to supply output signals to the following speakers: a front left speaker L, a front right speaker R, a center speaker C, a left surround speaker SRL, a right surround speaker SRR, and a sub-woofer SW. In the system shown in FIG. 2, the digital multi-channel audio signal A1c has the highest priority, and when present will match the analog stereo audio signal A1a (and thus A1) and thus will be selected. If not present, for example because the DVD is stereo only, or if the cable transporting the digital audio signal A1c is not present, the audio signal A5 may be a better signal. The audio signal A5 may only be present if the content provider first received information characterizing the audio output signal A1. This information may be sent always or only if no better audio signal is found. If the content provider has a better matching audio signal this is provided from the distant content source 8 of the content provider to the input I6r. The input I6r need not be an actual plug, it may, for example also be an infrared or other wireless receiver. The processor 4 may comprise a communication unit 7 being able to process the data which is received over the input I6r.

The receiver 3 may comprise a radio tuner (not shown), the output amplifiers need not be able to directly drive loudspeakers. A separate amplifier may be used to drive the loudspeakers.

Instead of comparing audio signals to find a match, also video signals may be compared. For example, the processor 4 (up till now referred to as audio processor) may also compare the video signal V2 with the video signal V1. If a match is found, the video signal which has the highest priority is selected and/or the associated one of the audio signals A1b, A1c may be selected. Or if several matches are found, for example if the content source 8 is also supplying a matching video signal the signal which has the highest priority is selected.

A further option may be that the receiver 3, if in stand-by, is activated when a signal is detected on one or particular ones of its inputs I1r to I6r. Further, the receiver 3 may switch to an input of which is detected that a signal becomes available. For example, the starting situation is that the audio source 6 is a CD player 6 which is active and the receiver 3 has selected the CD-player signal A3 to be outputted as the selected signal AS. Now the television receiver 2 is switched on, and the AV-receiver 3 detects that the signal A1 on the scart input I1r coupled via a scart cable to the TV receiver 3 becomes active. Now the AV- receiver 3 automatically switches over to this scart input I1r and starts searching for a matching signal present on another input I2r to I6r. The AV-receiver 3 stores the input which was active before the switch over. When the TV receiver 2 is switched off, the AV-receiver 3 selects the input of which is stored that it was active before the switch over.

FIG. 3 shows a detailed block diagram of an embodiment of the audio processor 4. All signals which have the same references as in FIG. 2 are identical to the signals of FIG. 2. The audio processor 4 comprises a comparator 41 which operates in the digital domain. The analog to digital converter 44 converts the analog stereo audio signal Al into a digital audio signal Aod. The multi-channel to stereo converter 45 converts the multi-channel analog audio signal A1b into an analog stereo audio signal A1bs. The analog to digital converter 46 converts the analog stereo audio signal A1bs into a digital stereo signal A1bd. The stereo or multi-channel digital audio signal A1e is fed directly to the comparator 41. If the audio signal A1c is a multi-channel signal it may be digitally processed in the comparator 41 to first obtain a digital stereo signal before the matching is checked. The multi-channel to stereo converter 47 converts the multi-channel analog audio signal A3 into an analog stereo audio signal A3s. The analog to digital converter 48 converts the analog stereo audio signal A3s into a digital stereo signal A3d. The protocol decoder 49 receives coded digital information A5 (for example, coded with the internet protocol, or with wireless protocols) and retrieves the stereo information A5s. The analog to digital converters 44, 46 and 48 may be separate circuits, or may be used in time multiplex.

Thus, now, all audio signals which are matched are digital stereo signals, and the quality of the matching is improved. The digital comparator 41 supplies the comparison signal to the controller 40. The controller 40 further may receive the priority information PI which is stored in the memory 43, and supplies the select signal SE to the selector 42. The selector 42 receives the input audio signals A1, A1b, A1c, A3 and A5 and supplies the selected audio signal AS which is one of the input audio signals A1, A1b, A1c, A3 and A5. Actually, the selector 42 may comprise an analog part for selecting the analog input audio signals, and a digital part for selecting the digital audio signals. Alternatively, the analog signals may be digitized and the selector 42 is a digital circuit.

FIG. 4 shows a detailed block diagram of another embodiment of the audio processor. All signals which have the same references as in FIG. 3 are identical to the signals of FIG. 3.

The audio processor 4 comprises a comparator 41 which now operates in the analog domain. The analog stereo audio signal A1 is directly fed to the comparator 41. The multi-channel to stereo converter 50 converts the analog multi-channel audio signal A1b into an analog stereo audio signal A1ba. The digital to analog converter 52 converts the stereo or multi-channel digital audio signal A1c into a stereo analog audio signal A1ca. If the audio signal A1c is a multi-channel signal it may be digitally processed in the digital to analog converter 52 to first obtain a digital stereo signal before it is converted into an analog stereo signal. The multi-channel to stereo converter 53 converts the multi-channel analog audio signal A3 into an analog stereo audio signal A3s. The protocol decoder 54 receives coded digital information A5 (again, for example, coded with the internet protocol, or with wireless protocols) and retrieves the digital stereo information A5d. The digital to analog converter 55 converts the digital stereo information A5d into the analog stereo audio A5a. The digital to analog converters 52 and 55 may be separate circuits, or may be used in time multiplex.

Thus, now, all audio signals which have to be matched are analog stereo signals, and the quality of the matching is improved. The analog comparator 41 supplies the comparison signal CS. The selector 42 (not shown, see FIG. 3) receives the input audio signals A1, A1b, A1c, A3 and A5 and supplies the selected audio signal AS which is one of the input audio signals A1, A1b, A1c, A3 and A5. Actually, the selector 42 may comprise an analog part for selecting the analog input audio signals, and a digital part for selecting the digital audio signals. Alternatively, the digital audio signals may be converted into analog audio signals and the selector 42 is an analog switching circuit.

In a preferred embodiment, the processor 4 receives a first audio and/or video signal A1, V1, and a second audio and/or video signal A2, V2; A1b, A1c, A3, A5. The comparator 41 compares the first audio or video signal A1; V1 and the second audio or video signal A2, A1b, A1c, A3, A5; V2, respectively, to detect a match between the first audio signal A1 and the second audio signal A2 or the first video signal V1 and the second video signal V2. A selector 42 supplies a selected signal AS which is the second audio or video signal A2, V2 if the match is detected or the first audio or video signal A1, V1 otherwise.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

Although the majority of embodiments and examples are directed to comparing audio signals to determine a match, video signals may be compared as well, although this involves a higher processing effort. The matching of signals need not be done with exactly the same signals. For example, a high correlation (directly or of the fingerprints) might be detected for one of the channels of a stereo audio signal and one of the channels of the multi-channel audio signal. For example if the DVD player supplies the center channel audio signal to TV-receiver, such that the loudspeakers of the TV-receiver are used as the center speaker, this center audio signal is used for finding a match. A reliable match may still be possible between this center audio signal and one or more channels of another audio signal, especially if the robust fingerprinting technique is used. Or, one of the components of component video may be compared with the luminance information of a S-VHS video signal.

Although with respect to FIGS. 3 and 4 is elucidated that the input signals can be received in parallel by the comparator 41, alternatively, the input signals may be selected one by one and the required pre-processing functions need to be present only once. Dependent on the nature of the input signal the correct pre-processing is selected or performed.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device 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

1. A processor (4) for receiving (I1) a first input signal (A1, V1) comprising a first audio signal (A1) and/or a first video signal (V1) and for receiving (I2) a second input signal (A2, V2; A1b, A1c, A3, A5) comprising a second audio signal (A2; A1b, A1c, A3, A5) and/or a second video signal (V2), the processor comprising: a comparator (41) for comparing the first input signal (A1, V1) and the second input signal (A2, V2; A1b, A1c, A3, A5) to detect a match between the first input signal (A1, V1) and the second input signal (A2, V2; A1b, A1c, A3, A5), and a selector (42) for supplying a selected signal (AS) being the second input signal (A2, V2; A1b, A1c, A3, A5) if the match is detected or being the first input signal (A1, V1) if no match is detected.

2. A processor (4) as claimed in claim 1, further comprising means (40) for receiving priority information (PI) indicating a priority between the first input signal (A1, V1) and the second input signal (A2, V2; A1b, A1c, A3, A5), and wherein the selector (42) is arranged for supplying the selected signal (AS) being the second input signal (A2, V2; A1b, A1c, A3, A5) if the match is detected and the priority indicates that the second input signal (A2, V2; Alb, A1c, A3, A5) is preferred above the first input signal (A1, V1), or for supplying the first input signal (A1, V1) otherwise.

3. A processor (4) as claimed in claim 1, comprising a first input (I1) for receiving the first input signal (A1, V1) from an external source (1) and a second input (I2) for receiving the second input signal (A2, V2; A1b, A1c, A3, A5) from said external source (1) or from a further external source, and wherein the processor (4) further comprises an output (O) for supplying the selected signal (AS).

4. A processor (4) as claimed in claim 1, wherein the comparator (41) comprises a cross-correlation determining circuit (41) for determining a cross-correlation between the first input signal (A1, V1) and the second input signal (A2, V2; A1b, A1c, A3, A5), the match being detected if the cross-correlation is higher than a predetermined value.

5. A processor (4) as claimed in claim 1, wherein the comparator (41) comprises a finger-print determining circuit (41) for determining a first fingerprint of the first input signal (A1, V1) and a second fingerprint of the second input signal (A2, V2; A1b, A1c, A3, A5), the match being detected if the first and the second fingerprint match.

6. A processor (4) as claimed in claim 1, wherein the first input signal (A1, V1) and second input signal (A2, V2; A1b, A1c, A3, A5) originate from a same source (1).

7. A processor (4) as claimed in claim 1, wherein the first input signal (A1, V1) is the first audio signal (A1) being a stereo audio signal, and wherein the second input signal (A2, V2; A1b, A1c, A3, A5) is the second audio signal (A2; A1b, A1c, A3, A5) being a multi-channel audio signal.

8. A processor (4) as claimed in claim 7, further comprising a decoder (45, 46, 50, 53) for converting the multi-channel audio signal into a further stereo signal, and wherein the comparator (41) is arranged for comparing the stereo audio signal and the further stereo signal.

9. A processor (4) as claimed in claim 1, wherein the first input signal (Al, V1) is the first audio signal (A1) being an analog audio signal, and wherein the second input signal (A2, V2; A1b, A1c, A3, A5) is the second audio signal (A2; A1c, A5) being a digital audio signal.

10. A processor (4) as claimed in claim 9, further comprising an analog to digital converter (44, 47) for converting the analog audio signal into a further digital audio signal, and wherein the comparator (41) is arranged for comparing the further digital audio signal with the digital audio signal.

11. A processor (4) as claimed in claim 1, wherein the first input signal (A1, V1) is the first audio signal (A1), and wherein the second input signal (A2, V2; A1b, A1c, A3, A5) is the second audio signal (A2; A1b, A1c, A3, A5).

12. A processor (4) as claimed in claim 1, wherein the first input signal (A1, V1) is the first video signal (V1), and wherein the second input signal (A2, V2; A1b, A1c, A3, A5) is the second video signal (V2).

13. A receiver (3) comprising the processor (4) as claimed in claim 1, the receiver (3) having a first receiver input (I1r) for receiving the first input signal (A1, V1), a second receiver input (I2r) for receiving the second input signal (A2, V2; A1b, A1c, A3, A5), and a receiver output (Q1, Q2, Q3, Q4, Q5, Q6) for supplying an output audio signal (L, R, C, SRL, SRR, SW) being related to the selected signal (AS).

14. A receiver (3) as claimed in claim 13, wherein the processor (4) further comprises a wireless or wired communication unit (7) for communicating with an external information source (8) to receive the second input signal (A5).

15. A system comprising: an audio-video source (1) for supplying a first audio output signal (A1a) and a first input video signal (V1a);a display apparatus (2) having a video input for receiving the first input video signal (V1a) to supply the first video signal (V1) being related to first input video signal (V1a), and/or an audio input for receiving the first audio input signal (A1a) to supply the first audio signal (A1) being related to the first audio input signal (A1a), an image processor (23) for processing the first video signal (V1) to obtain a display signal (DS), a display (24) for displaying the display signal (DS); anda receiver (2) as claimed in claim 13 being physically separated from the display apparatus (2).

16. A system as claimed in claim 15, wherein the audio-video source (1) is arranged for also supplying the second audio signal (A2) being different than, but related to, the first audio signal (A1).

17. A method of processing comprising receiving (I1, I2) a first input signal (A1, V1) comprising a first audio signal (A1) and/or a first video signal (V1) and a second input signal (A2, V2; A1b, A1c, A3, A5) comprising a second audio signal (A2; A1b, A1c, A3, A5) and/or a second video signal (V2), comparing (41) the first input signal (A1, V1) and the second input signal (A2) to detect a match between the first input signal (A1, V1) and the second input signal (A2), and supplying (42) a selected signal (AS) being the second input signal (A2) if the match is detected or being the first input signal (A1, V1) if no match is detected.