METHOD FOR GENERATING A CONVERSION FILTER FOR CONVERTING A MULTIDIMENSIONAL OUTPUT AUDIO SIGNAL INTO A TWO-DIMENSIONAL AUDIO SIGNAL FOR LISTENING

Abstract

The present invention relates to methods for generating a conversion filter (KF) for converting a multidimensional original audio signal (AA) into a two-dimensional listening audio signal (HA), comprising the following steps: 1. Transformation of a time-based original audio signal (PAA) into a frequency-based original audio signal (FAA) 2. Sequential optimization of a basis conversion matrix (BKM) for converting the frequency-based original audio signal (FAA) into a frequency-based listening audio signal (FHA) using a first optimization algorithm (KA1), preferably starting from low frequencies and ascending at least up to a switching frequency (UF) 3. Sequential optimization of the basis conversion matrix (BKA) for converting the frequency-based original audio signal (FAA) into a frequency-based listening audio signal (FHA) using a second optimization algorithm (KA2), preferably starting from the switching frequency (UF) and ascending to high frequencies 4. Storing the optimized basis conversion matrix (BKA) of the correlation between the frequency-based original audio signal (FAA) and the frequency-based listening audio signal (FHA) in a frequency-based conversion matrix (FKM) 5. Transforming the frequency-based conversion matrix (FKM) into a time-based conversion matrix (PKM) as a conversion filter (KF).

Claims

1. Method for generating a conversion filter (KF) for converting a multidimensional original audio signal (AA) into a two-dimensional listening audio signal (HA), comprising the following steps: transforming a time-based original audio signal (PAA) into a frequency-based original audio signal (FAA); sequentially optimizing a basis conversion matrix (BKM) for converting the frequency-based original audio signal (FAA) into a frequency-based listening audio signal (FHA) using a first optimization algorithm (KA1), preferably starting from low frequencies and ascending to at least a switch frequency (UF); sequentially optimizing the basis conversion matrix (BKA) for converting the frequency-based original audio signal (FAA) into a frequency-based listening audio signal (FHA) using a second optimization algorithm (KA2), preferably starting from the switch frequency (UF) and ascending to high frequencies; storing the optimized basis conversion matrix (BKA) of the correlation between the frequency-based original audio signal (FAA) and the frequency-based listening audio signal (FHA) in a frequency-based conversion matrix (FKM); transforming the frequency-based conversion matrix (FKM) into a time-based conversion matrix (PKM) as the conversion filter (KF).

2. The method of claim 1, characterized in that a predefined fixed switch frequency (FUF) is specified as the switch frequency (UF).

3. The method according to claim 1, characterized in that at least sectionally, in particular completely from low frequencies to the switch frequency (UF), the first optimization algorithm (KA1) and the second optimization algorithm (KA2) are carried out in parallel, with the difference between the two optimization results, in particular with respect to the same error measure, being determined as the optimization error of the first optimization algorithm (KA1).

4. The method of claim 3, characterized in that, for storage in the frequency-based conversion matrix (FKM), the result of the first optimization algorithm (KA1) with a variable switch frequency (VUF) is stored until a predefined error limit is reached, and from this variable switch frequency (VUF) onwards, the result of the second optimization algorithm (KA2) is stored.

5. The method of claim 4, characterized in that only the second optimization algorithm (KA2) is applied above the variable switch frequency (VUF).

6. The method according to characterized in that only the first optimization algorithm (KA1) is used starting from low frequencies up to a frequency limit below the variable switch frequency (VUF).

7. The method according to claim 3, characterized in that a range of variable switch frequencies (VUF) of these optimization procedures is stored as the expected switch frequency (UF) based on multiple optimization procedures.

8. The method according to claim 1, characterized in that the first optimization algorithm (KA1) is phase-dependent and the second optimization algorithm (KA2) is phase-independent.

9. The method according to claim 1, characterized in that at least one of the following specification parameters is used for the two optimization algorithms (KA1, KA2): recording profile (AP) specific to the geometric recording arrangement; listener group profile (HGP) specific to a certain listener group; listener individual profile (HPP) specific to a specific listener.

10. The method according to claim 1, characterized in that at least partially a real recorded multidimensional audio signal is used as the original audio signal (AA).

11. The method according to claim 1, characterized in that a digitally generated audio signal is used at least partially as the multidimensional original audio signal (AA).

12. The method according to claim 1, characterized in that the two-dimensional listening audio signal (HA) is designed as a left-right audio signal.

13. The method according to claim 1, characterized in that the method steps are carried out at least twice for different orientations of the two-dimensional listening audio signal (HA).

14. A computer program product comprising commands which, when executed by a computer, cause the steps of the method according to claim 1 to be performed.

15. Conversion method for converting a multidimensional original audio signal (AA) into a two-dimensional listening audio signal (HA), comprising the following step: Applying a conversion filter (KF) generated by a method having the features of claim 1 to the original audio signal (AA) for conversion into the listening audio signal (HA).

Description

[0049] FIG. 1 shows an embodiment of the inventive conversion method,

[0050] FIG. 2 shows an embodiment during the recording of original audio signals,

[0051] FIG. 3 shows a representation during the playback of listening audio signals,

[0052] FIG. 4 shows a first step of an inventive method,

[0053] FIG. 5 shows a further step of an inventive method,

[0054] FIG. 6 shows another step of an inventive method,

[0055] FIG. 7 shows a detailed representation of a step of an inventive method,

[0056] FIG. 8 shows a further detailed representation of a step of an inventive method, and

[0057] FIG. 9 shows a further detailed representation of a step of an inventive method.

[0058] In FIG. 1, it is shown schematically how multidimensional original audio signals AA can be converted into a plurality of individual data lines. For this purpose, a conversion device 10 is provided, which is capable of performing a conversion into a two-dimensional listening audio signal HA in a computationally efficient manner using a conversion filter KF. This conversion is performed independently of the optimization algorithms KA1 and KA2 explained above and leads to two audio signals for the left and the right ear. The application of these signals is based on a multidimensional recording, as shown, for example, in FIG. 2.

[0059] FIG. 2 shows a microphone array as a recording device 20 schematically. Here, a spherical dummy head is depicted as the recording device 20, on the surface of which a plurality of individual microphones 22 are arranged. Each of these individual microphones 22 records a sound track in a recording situation, with all sound tracks together, shown on the right in FIG. 2, forming the multidimensional original audio signal AA. The actual arrangement of the microphones 22 and the overall geometry of the recording device 20 represent the specification in the form of a recording profile AP.

[0060] FIG. 3 shows how the listening situation appears. A schematically depicted head of a listener is here equipped with headphones as playback device 30. This playback device 30 has a left headphone output and a right headphone output as audio output means 32. Either a listener group profile HGP or a listener individual profile HPP is specified here as a specification for the listening profile, specifically for a listener group or the exact listener. A left soundtrack and a right soundtrack are played back here, which together form the two-dimensional listening audio signal HA in this embodiment.

[0061] In order to carry out the conversion into the necessary two-dimensional listening audio signal HA using a conversion filter KF that is computationally efficient, an inventive method is performed beforehand.

[0062] FIG. 4 shows how, in a first step, the time-based original audio signal PAA is converted into a frequency-based original audio signal FAA. This can be a real audio signal or a virtual audio signal. Multiple directions are provided for each channel, allowing for large channel numbers of 1000 or more. For example, a Fast Fourier Transform can be used. The number of audio tracks for each direction remains preferably the same and thus unchanged in this first transformation step.

[0063] In the subsequent step of the inventive method, the actual conversion takes place. As shown in FIG. 5, at least two different optimization algorithms KA1 and KA2 are used. Using the basis conversion matrix, the conversion to the frequency-based listening audio signal FHA is carried out, which is schematically shown with two channels for one direction. For example, if 1000 directions are used for the method, this conversion will result in 2000 individual channels for the frequency-based listening audio signal FHA. The result of the optimization algorithms is stored in the frequency-based conversion matrix FKM in the form of the optimized basis conversion matrix BKM.

[0064] FIG. 6 shows the final step, in which a time-based conversion matrix PKM is generated from the frequency-based conversion matrix FKM through inverse transformation, which can then be used as a conversion filter KF in the conversion task of a conversion process.

[0065] FIG. 7 shows a way in which the different optimization algorithms KA1 and KA2 can be used. Here, a single audio track of the frequency-based original audio signal FAA is shown schematically. A sharp separation is given for a fixed switching frequency FUF as a switching frequency UF, so that starting from the lowest frequency, only the first optimization algorithm KA1 is used sequentially. When the switching frequency UF is reached, the process switches to the second optimization algorithm KA2, so that only the second optimization algorithm KA2 is used for the higher frequencies starting from the fixed switching frequency FUF.

[0066] FIG. 8 shows the described possibility of a completely parallel implementation of the optimization algorithms KA1 and KA2. However, only the qualitatively better optimization result is used for storage in the respective frequency-based conversion matrix FKM. In particular, a comparison of the optimization results at the same frequencies is performed based on the parallel implementation of the optimization.

[0067] FIG. 9 shows a way to reduce this double conversion, so that for example, only the first optimization algorithm KA1 is used at the beginning of the conversion. Over a certain period of time in the form of a frequency range, parallel acquisition takes place, for example, from a frequency threshold value, and the variable switching frequency VUF is set once the optimization error exceeds a predefined error threshold. From this variable switching frequency VUF, only the second optimization algorithm KA2 is used, so that compared to the embodiment of FIG. 8, the frequency range in which the parallel and thus double optimization must take place could be significantly reduced.

[0068] The above explanation describes the present invention solely within the scope of examples. Of course, individual features of the embodiments can be freely combined with each other, if technically feasible, without departing from the scope of the present invention.

REFERENCE SYMBOL LIST

[0069] 10 Conversion Device [0070] 20 Recording Device [0071] 22 Microphone [0072] 30 Playback Device [0073] 32 Audio Output Device [0074] AP Recording Profile [0075] HGP Listener Group Profile [0076] HPP Listener Individual Profile [0077] KF Conversion Filter [0078] BKM Base Conversion Matrix [0079] FKM Frequency-based Conversion Matrix [0080] PKM Time-based Conversion Matrix [0081] KA1 First Conversion Algorithm [0082] KA2 Second Conversion Algorithm [0083] AA Original Audio Signal [0084] PAA Time-based Original Audio Signal [0085] FAA Frequency-based Original Audio Signal [0086] HA Listening Audio Signal [0087] FHA Frequency-based Listening Audio Signal [0088] UF Switching Frequency [0089] FUF Fixed Switching Frequency [0090] VUF Variable Switching Frequency