Processing microphone generated signals to generate surround sound

• US 20080170728A1
• Filed: 01/12/2007
• Published: 07/17/2008
• Est. Priority Date: 01/12/2007
• Status: Active Grant

• Current Assignee: Fraunhofer-Gessellschaft Zur Foerderung Angewandten Forschung E.V.
• Original Assignee: Fraunhofer-Gessellschaft Zur Foerderung Angewandten Forschung E.V.
• Inventors: Faller, Christof
• Granted Patent: US 8,041,043 B2
• Time in Patent Office: Days
• US Class Current: 381/182
• CPC Class Codes: H04R 5/027 Spatial or constructional arrangements of microphones, e.g. in dummy heads
• CPC Class Codes: H04S 5/005 of the pseudo five- or more-channel type, e.g. virtual surround

Abstract

Surround sound recording is a tedious task requiring the use of many microphones. The invention aims at enabling the use of two-channel microphones (or stereo microphones) for multi-channel surround recording. A conventional stereo microphone, or a two-channel microphone specifically optimized for use with the proposed algorithm, is used to generate two signals. A post-processor is applied to the microphone generated signals to convert them to multi-channel surround.

This aim is achieved through a method to generate multiple output audio channels (y1, . . . , yM) from two microphone generated audio channels (x1, x2), in which the number of output channels is equal or higher than two, this method comprising the steps of:

• • determine directions of sound components related to the microphone characteristics
  • determine compensation gains of sound components related to the microphone characteristics
  • generating the output audio channels, y1, . . . , yM, by using the microphone generated audio channels, x1, x2, directions, and compensation gains

Claims

1. Method to generate multiple output audio channels (y1, . . . , yM) from two microphone generated audio channels (x1, x2), in which the number of output channels is equal or higher than two, this method comprising the steps of:

determining directions of sound components related to the microphone characteristics

determining compensation gains of sound components related to the microphone characteristics

generating the output audio channels, y1, . . . , yM, by using the microphone generated audio channels, x1, x2, directions, and compensation gains

2. Method of claim 1, whereas the directions of sound components are determined as a function of amplitude ratios of the microphone generated signals.

3. Method of claim 1, whereas the directions of sound components are determined as a function of phase relations between the microphone generated signals.

4. Method of claim 1, whereas the compensation gains are determined related to the sum of the responses of the microphones.

5. Method of claim 1, whereas the output audio channels are a surround sound audio signal.

6. Method of claim 1, whereas for generating the output audio channels a matrix decoder is used.

7. Method of claim 1, whereas the microphone generated audio channels are decomposed into direct sound, ambient sound, and a measure related to direction of direct sound.

8. Method of claim 1, whereas the processing is carried out in a plurality of subbands, and the directions of sound components and compensation gains are estimated in each subband as a function of time.

9. Device to generate multiple output audio channels (y1, . . . , yM) from two microphone generated audio channels (x1, x2), in which the number of output channels is equal or higher than two, this device comprising:

first calculation means to determine directions of sound components related to the microphone characteristics

second calculation means to determine compensation gains of sound components related to the microphone characteristics

third calculation means for generating the output audio channels, y1, . . . , yM, by using the microphone generated audio channels, x1, x2, directions, and compensation gains

10. Device of claim 9, wherein the directions of sound components of the first calculation means are determined as a function of amplitude ratios of the microphone generated signals.

11. Device of claim 9, whereas the directions of sound components of the first calculation means are determined as a function of phase relations between the microphone generated signals.

12. Device of claim 9, wherein the compensation gains of the second calculation means are determined related to the sum of the responses of the microphones.

13. Device of claim 9, wherein it comprises a splitting means to convert the input signal into a plurality of subbands and the first, second, and third calculation means are acting on each subband as a function of time.