EP2139133A2 - Device and method for matching the playback spectrum of two audio sources - Google Patents

Abstract

The device has an adaptive filter (3) including two inputs and an output. Transfer function elements (32, 33) render audio sources (1, 2) at inputs of the filter. The function element (32) is adjustable by a user and the function element (33) is automatically established such that a rendering spectrum at the output of the filter is same for both the audio sources. A memory device stores the transfer function elements. Conformity memories (30, 31) store a portion of signals of the sources. An integrator (7) determines the spectrum at the output and/or a signal spectrum of the source (2). Independent claims are also included for the following: (1) a method for switching audio sources (2) a computer program with a program code stored on a machine-readable medium for executing a method for switching audio sources.

Description

The invention relates to a device for adapting the reproducible spectrum of two audio sources, comprising an adaptive filter having a first and a second input and an output, wherein a first transfer function for reproducing the first audio source at the first input and a second transfer function for reproducing the second audio source is provided at the second input.

Devices of the type mentioned are used in particular to play different audio sources with the same program content alternately, with no noticeable switching effects should occur for the listener.

From the DE 101 03 400 A1 It is known to provide a radio receiver with an analog and a digital receiver. Often identical program content is disseminated via both analogue and digital channels. The previously known radio receiver always selects the transmission path available at the respective location with the highest quality and automatically switches to a different transmission path when the transmission deteriorates.

If there is a time offset between nominally identical program contents, this time offset is taken into account during the switchover, so that no noticeable switching effects occur for the listener. Furthermore, it is proposed in the prior art to determine a difference in volume between the transmission paths and to adjust the volume of the audio sources during the switching.

It is also known to provide variable filter stages as a tone control, by means of which the user can raise or lower individual frequency ranges of the input signal in order to adapt the signal to his listening habits and his personal preferences. However, if the signal of the first audio source and the signal of the second audio source are different bandwidth, i. have a different frequency spectrum, results due to the changing in the switching of the transmission path input signal despite the sound adjustment by the user a different sound impression. The user must compensate for this difference after switching so by manually operating the tone controls again.

The invention is therefore based on the object to make the remaining prior art switching effects as far as possible inaudible to the user the task.

The object is achieved by a device for adjusting the reproducible spectrum of two audio sources, comprising an adaptive filter having a first and a second input and an output, wherein a first transfer function for reproducing the first audio source at the first input and a second transfer function for playback the second audio source is provided at the second input, wherein the first transfer function is adjustable by the user, and the second transfer function is automatically determined, so that the playback spectrum at the output of the adaptive filter is the same for both audio sources.

Furthermore, the object is achieved in a method for switching two audio sources of the same program content, in which an adaptive filter with a first transfer function for reproducing the first audio source and a second transfer function of the second audio source is used to the playback spectrum at the output of the adaptive filter for both To equalize audio sources, wherein the first transfer function is set by the user and the second transfer function is determined automatically.

According to the invention, it is proposed to provide a filter with variable transmission behavior for individual sound adjustment by the user. This allows the user to customize the playback to their individual needs. After the switching of the audio signal, for example, from an analog radio receiver to a digital radio receiver or vice versa results in a different output signal due to the different bandwidth of both signal sources with unchanged filter function. In the prior art, the user would have to make the sound settings again, i. change the transfer function of the filter to replay according to its individual preferences.

According to the invention, it is now proposed to analyze the playback spectrum at the output of the filter and, by analyzing the input spectrum of the second audio source, to calculate a second filter function and to store it in a memory before the switchover. In this way, the transfer function of the filter can be switched simultaneously with the audio source, so that the playback spectrum remains almost unchanged.

A virtually unchanged or equal reproduction spectrum in the sense of the present invention is understood to mean a reproduction spectrum which causes the same sound impression to the user or listener. This does not exclude that two reproduction spectra have partly different signal intensities in one or more frequency bands, if these differences are not perceived by the user, for example due to psychoacoustic effects or due to the inaudibility of frequencies at the edge of the reproduction spectrum.

In one embodiment of the invention can be provided, for each broadcast program, a first and a second transfer function store in a storage device. If the user makes no changes to the sound settings when the corresponding broadcast program is called up, the program can be played back immediately with the stored transfer function and thus with the sound settings preferred by the user. The radio receiver with the inventive device selects depending on the input signal, for example, as a function of a digital or an analog transmission path, the appropriate transfer function.

Figur 1

zeigt dabei ein Blockschaltbild der erfindungsgemäßen Vorrichtung zur Umschaltung zweier Audioquellen.

Figur 2

zeigt ein Blockdiagramm des erfindungsgemäßen Verfahrens zur Umschaltung zweier Audioquellen.

The invention will be explained in more detail with reference to figures without limiting the general inventive concept.

FIG. 1

shows a block diagram of the device according to the invention for switching two audio sources.

FIG. 2

shows a block diagram of the inventive method for switching two audio sources.

In FIG. 1 a device according to the invention for switching two audio sources is shown schematically. In the embodiment according to FIG. 1 For example, the two audio sources 1 and 2 comprise two broadcast receiving parts, for example, an analog broadcast receiver 1 and a digital broadcast receiver 2. Each broadcast receiver is provided with an antenna for receiving a broadcast signal intended for it. After demodulation of the broadcast signal from the carrier frequency and optionally after analog / digital or digital / analog conversion of the signal, both audio signals are available at two inputs of an adaptive filter 3.

The adaptive filter 3 can be constructed as an analog or digital filter. An analog filter can be constructed as a passive filter consisting of resistors, capacitors and inductors. An active analog filter may have filter stages, for example, which operate with at least one operational amplifier. A digital filter can be realized by means of a digital signal processor or a microprocessor, which executes a corresponding software, which represents the desired filter characteristic.

The adaptive filter 3 has a conformance memory 30 and 31 at each input. The conformity memory is used for buffering the input signals of the audio sources 1 and 2, for example in the form of a FIFO stack. The data read from the conformity memory 30 are convolved with a filter function 32. This can be done either in the form of analog or digital filtering, for example with a digital signal processor. In FIG. 1 In this case, the situation is shown that the data arrive at the output of the filter 32 via a changeover switch 34 to the output of the adaptive filter 3.

The transfer function 32 of the first signal path can be set by the user via a user interface 6. For example, the user may individually raise or lower individual frequency bands such as bass, mid or high according to his preferences.

The transfer function 32 changes the sound spectrum of the input signal of the first audio source 1 at the output of the adaptive filter 3. This output signal is subsequently supplied to a signal amplifier 4. The signal amplified in the signal amplifier 4 is then reproduced via at least one loudspeaker 5.

For clarity, is in FIG. 1 only one signal amplifier with a loudspeaker dargstellt. It will be understood by those skilled in the art that multiple signal amplifiers and multiple speakers may be used for playback, for example for stereo playback or to use separate loudspeakers for the bass, midrange and treble ranges.

After the user-desired sound adaptation, d. H. the definition of the transfer function 32 is completed via the user interface 6, the arithmetic unit 7 analyzes the reproduction spectrum at the output of the transfer filter 3. This can be done for example by means of a Fourier or a wavelet transformation. The arithmetic unit 7 contains, for example, a semiconductor memory and / or a digital signal processor and / or a microprocessor and / or a microcontroller and corresponding software.

In the same way, the input signal of the second audio source 2 is analyzed. For this purpose, the arithmetic unit 7 reads data from the audio source 2 from the conformity memory 31.

The arithmetic unit 7 then determines from the differences of the respective signal spectra a transfer function 33 which is suitable for converting the signal of the second audio source 2 into the reproduction spectrum. The transfer function 33 is thus used to reproduce the nominal content-identical audio signal of the audio source 2 in such a way that the same playback spectrum is available at the output of the adaptive filter 3 even with different input spectra of the audio sources 1 and 2. For this purpose, the arithmetic unit 7 may also comprise a unit known per se in order to equalize the volume and / or a time offset between the signals of the audio sources 1 and 2.

After the transfer function 33 has been determined, both transfer functions 32 and 33 can be stored in an in FIG. 1 Memory not shown are stored. Together with the transfer functions 32 and 33, an identifier is generated and stored, which assigns the transfer functions 32 and 33 to a specific radio program. In a development of the invention, further information can also be stored in the memory, for example a time offset between audio sources with a nominally identical program content.

As long as the user makes no changes to the transfer function 32 via the control element 6, stands the stored, user-preferred sound impression for this broadcast program available, regardless of whether this program is played on the audio source 1 or the audio source 2. Due to the automatically determined transfer function 33, this sound impression does not change when switching between the two audio sources 1 and 2 by means of the switch 34.

The switch 34 can either automatically switch from the first to the second audio source, for example from a digital radio receiver to an analog radio receiver, if the signal of the currently not reproduced audio source better reception, i. promises a better sound impression. Alternatively, the switching can also be done manually by an intervention of the user.

In one embodiment of the invention can be provided to make the structure of the adaptive filter 3 symmetric, d. H. also let the user specify the transfer function 33 by means of the user interface 6 and instead to automatically generate the transfer function 32 as described above.

FIG. 2 shows a flow chart of the proposed method according to the invention. First, both the first and the second audio signal are buffered in a conformity memory 2. The buffering preferably comprises a data amount which allows playback for about 0.5 to 15 seconds. Preferably, the buffering of the audio signals takes place in the form of digital signals.

Upon completion of caching, a playback source is automatically selected. Since both the first and the second audio signal transmit the same program content, the selection of the playback source is based on the quality of the audio signals. For example, if the signal voltage of an analog received audio signal is very low, a digital audio signal is preferred selected. If a digital audio signal can only be transmitted with a high bit error rate, an analog audio signal is preferably selected.

It is then checked whether a transfer function for the selected audio source and / or the program content intended for reproduction has already been stored in the memory device assigned to the device. If the transfer functions have already been deposited, the transfer function assigned to the respective audio source is selected and the audio source is reproduced on the audio signal using the transfer function.

If no transfer function could be found for the desired program content, the audio signal of the selected audio source is reproduced without the use of a transfer function. Playback now takes place with the sound settings provided by the transmitter or a default setting of the first transfer function.

If the user wishes to adapt the sound impression to his individual listening habits, he can achieve this by adapting the first transfer function, which is intended to reproduce the first audio source. The setting of the transfer function here comprises in particular the lowering or raising of selectable frequency ranges of the audio signal. After completion of the setting of the first transfer function by the user, this first transfer function is stored in a storage device.

It should be noted that the setting of the transfer function by the user is not mandatory, but the user can be satisfied with the sound settings provided by the transmitter or the default setting stored in the radio receiver. In this case, the first transfer function may be a constant function that does not change the audio signal provided by the first audio source.

After the transfer function has been stored, the first audio source is played using the user-selected first transfer function. The transfer function thereby changes the spectrum of the input signal to a reproduction spectrum, for example by folding the input signal with the transfer function.

The playback spectrum is now analyzed by means of an arithmetic unit, for example by means of a digital signal processor. Furthermore, the spectrum of the input signal supplied by the non-selected signal source is analyzed in the same way. In the illustrated embodiment, this is the second audio signal. The analysis can be carried out, for example, by a Fourier transformation, a Hilbert transformation or a wavelet transformation of the audio signals.

Based on the analysis of the reproduction spectrum and the analysis of the input signal spectrum of the non-selected signal source, a transfer function is now calculated, which converts the spectrum of the non-selected signal source into the reproduction spectrum. If the spectrum of the input signal of the first audio source and the second audio source is identical, an identity of the first and the second transfer function also results. If the spectrum of both audio sources is not identical, there are differences in the transfer functions, which convert these different input spectra into an identical reproduction spectrum.

After the second transfer function has also been calculated, the first transfer function is stored together with the second transfer function and an identifier characterizing the program content. Thus, the transfer functions, which map the individual listening habits of the user while eliminating the tonal differences of the audio sources, are available for future use. Only when a transfer function is changed by a user intervention, a second transfer function is automatically calculated again, which also maps these changes.

If the signal strength of the selected audio source decreases so much that a reproduction of the program content by means of the second audio source promises a better reproduction quality, both the audio source and the associated transfer function are changed so as to enable a reproduction with an identical reproduction spectrum.

Claims (11)

Device for switching over two audio sources (1, 2), comprising an adaptive filter (3) having a first and a second input and an output, wherein a first transfer function (32) for reproducing the first audio source (1) at the first input and a second transfer function (33) for playback of the second audio source (2) is provided at the second input, characterized in that the first transfer function (32) is adjustable by the user and the second transfer function (33) can be determined automatically, so that the playback spectrum on Output of the adaptive filter (3) for both audio sources (1, 2) is the same. Apparatus according to claim 1, characterized in that further comprises a memory device is provided, by means of which the first and the second transfer function can be stored. Device according to one of claims 1 or 2, characterized in that the first or the second audio source (1, 2) comprises an analog radio receiver and the second or the first audio source (2, 1) comprises a digital radio receiver. Apparatus according to claim 2 and 3, characterized in that the memory device is adapted for each broadcast program, which is receivable both by means of the analog radio receiver (1) and by means of the digital radio receiver (2), a first and a second transfer function (33 , 32) to save. Device according to one of claims 1 to 4, characterized in that a conformity memory (30, 31) is present, in which at least part of the signals of the first and the second audio source (1, 2) can be stored and an analysis device (7) is present is, with which the playback spectrum at the output of the adaptive filter and / or the signal spectrum of an audio source (2) can be determined. Method for switching over two audio sources (1, 2) of the same program content, in which an adaptive filter (3) having a first transfer function (32) for reproducing the first audio source (1) and a second transfer function (33) for reproducing the second audio source (2 ) is used to equalize the reproduction spectrum at the output of the adaptive filter (3) for both audio sources (1, 2), characterized in that the first transfer function (32) is set by the user and the second transfer function (33) is determined automatically. A method according to claim 6, characterized in that a conformity memory (30, 31) is used to at least partially store the signals of the first and second audio sources (1, 2), wherein after the setting of the first transfer function (32) the reproduction spectrum determined at the output of the adaptive filter (3) and the signal spectrum of the second audio source (2) and the second transfer function (33) is automatically set so that for the second audio source (2) results in the same playback spectrum. Method according to one of claims 6 or 7, characterized in that the first and the second transfer function (32, 33) is stored. A method according to claim 8, characterized in that the first or the second audio source (1, 2) comprises an analogue radio receiver and the second or the first audio source (2, 1) comprises a digital radio receiver and for each broadcasting program, which by means of both the analogue Broadcasting receiver as well as by means of the digital radio receiver is receivable, a first and a second transfer function (32, 33) is stored. Computer program with program code, which is stored on a machine-readable carrier, for carrying out the method according to one of claims 6 to 9, when the computer program is executed on a computer. Radio receiver with a device according to one of claims 1 to 5.

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