Low coding rate parametric spatial audio encoding

Abstract

An apparatus configured to: receive a direction value for a time frame of an audio object; compare, as a first comparison, a bit allocation against a threshold bit allocation value; depending on the first comparison, either quantize the direction value for the time frame of the audio object with a quantizer according to the bit allocation, or compare, as a second comparison, the direction value for the time frame of the audio object with a direction value for a previous time frame of the audio object; and depending on the second comparison quantize the direction value for the time frame with the quantizer according to the bit allocation and signal the second comparison.

Description

Abstract A device is configured to: receive a direction value of a time frame of an audio object; compare a bit allocation with a threshold bit allocation value as a first comparison; depending on the first comparison, quantize the direction value of the time frame of the audio object with the bit allocation using a quantizer, or compare the direction value of the time frame of the audio object with the direction value of a previous time frame of the audio object as a second comparison; and depending on the second comparison, quantize the direction value of the time frame with the bit allocation using the quantizer and signal the second comparison.

Claims

CLAIMS:1 . An apparatus comprising means configured to: receive a direction value for a time frame of an audio object; compare, as a first comparison, a bit allocation against a threshold bit allocation value; depending on the first comparison, either quantize the direction value for the time frame of the audio object with a quantizer according to the bit allocation, or compare, as a second comparison, the direction value for the time frame of the audio object with a direction value for a previous time frame of the audio object; and depending on the second comparison quantize the direction value for the time frame with the quantizer according to the bit allocation and signal the second comparison.

2. The apparatus as claimed in Claim 1 , wherein the means configured to depending on the second comparison quantize the direction value for the time frame with the quantizer according to the bit allocation and signal the comparison is configured to: quantize the direction value for the time frame with the quantizer according to the bit allocation when the second comparison indicates the direction value for the time frame of the audio object is different from the direction value for the previous time frame of the audio object and set a signal flag to indicate that the direction value for the time frame differs from the direction value for the previous time frame; and set a signal flag to indicate that the direction value for the time frame is the same as the direction value for the previous time frame when the second comparison indicates the direction value for the time frame of the audio object is the same as the direction value for the previous time frame of the audio object.

3. The apparatus as claimed in Claims 1 and 2, wherein the means configured to depending on the first comparison, either quantize the direction value for the time frame of the audio object with a quantizer according to the bit allocation, orcompare, as a second comparison, the direction value for the time frame of the audio object with a direction value for a previous time frame of the audio object is configured to: quantize the direction value for the time frame of the audio object with a quantizer according to the bit allocation when the bit allocation for the quantization of the direction value is not less than the threshold bit allocation value; and compare the direction value for the time frame of the audio object with a direction value for a previous time frame of the audio object as the second comparison when the bit allocation for the quantization of the direction value is less than the threshold bit allocation value.

4. The apparatus as claimed in Claims 1 to 3, wherein the quantizer is a spherical grid quantizer wherein the spherical grid is formed by covering the sphere with smaller spheres, wherein the smaller spheres define the points of the spherical grid.

5. The apparatus as claimed in Claims 1 to 4, wherein the direction value comprises an azimuth value and an elevation value.

6. An apparatus comprising means configured to: compare a bit allocation for a direction value index for a time frame of an audio object against a threshold bit allocation value; depending on the comparison, either decode the direction value index for the time frame of the audio object with a de-quantizer according to the bit allocation, or read a state of a signal flag associated with the direction value index for the time frame of the audio object; and depending on the state of the signal flag; either set a quantized direction value for the time frame of the audio object to be a quantized direction value for a previous time frame of the audio object, or decode the direction value index for the time frame of the audio object with a de-quantizer according to the bit allocation giving a quantized direction value for the time frame of the audio object and adjust an azimuthvalue of the quantized direction value for the time frame of the audio object in accordance with a quantization resolution of the azimuth value.

7. The apparatus as claimed in Claim 6, wherein the means configured to adjust an azimuth value of the quantized direction value for the time frame of the audio object in accordance with a quantization resolution of the azimuth value is configured to: compare the product of the azimuth value of the quantized direction value for the time frame and an azimuth value of the quantized direction value for the previous time frame of the audio object, and when the product is greater than zero: determine a difference between two consecutive azimuth quantization values of the de-quantizer; when a difference between the azimuth value of the quantized direction value for the time frame and the azimuth value of the quantized direction value for the previous time frame of the audio object is greater than half the difference between two consecutive azimuth quantization values of the de-quantizer subtract the half difference between two consecutive azimuth quantization values of the de-quantizer from the azimuth value of the quantized direction value for the time frame of the audio object; and when a difference between the azimuth value of the quantized direction value for the previous time frame and the azimuth value of the quantized direction value for the time frame of the audio object is greater than half the difference between two consecutive azimuth quantization values of the de-quantizer add the half difference between two consecutive azimuth quantization values of the de-quantizer to the azimuth value of the quantized direction value for the time frame of the audio object.

8. The apparatus as claimed in Claim 7, wherein the means configured to determine a difference between two consecutive azimuth quantization values of the de-quantizer is configured to: divide the circumference of a circle by a number of azimuth values, where the number of azimuth values is determined by the elevation value of the quantized direction value for the time frame.

9. The apparatus as claimed in Claims 6 to 8, wherein the state of the signal flag indicates one of: a direction value for the time frame of the audio object differs from a direction value for the previous time frame of the audio object; or a direction value for the time frame of the audio object is the same as a direction value for the previous time frame of the audio object;10. The apparatus as Claimed in Claims 6 to 9, wherein the de-quantizer is a spherical grid quantizer wherein the spherical grid is formed by covering the sphere with smaller spheres, wherein the smaller spheres define the points of the spherical grid.

11. A method comprising: receiving a direction value for a time frame of an audio object; comparing, as a first comparison, a bit allocation against a threshold bit allocation value; depending on the first comparison, either quantizing the direction value for the time frame of the audio object with a quantizer according to the bit allocation, or comparing, as a second comparison, the direction value for the time frame of the audio object with a direction value for a previous time frame of the audio object; and depending on the second comparison quantizing the direction value for the time frame with the quantizer according to the bit allocation and signal the second comparison.

12. The method as claimed in Claim 11 , wherein depending on the second comparison quantize the direction value for the time frame with the quantizer according to the bit allocation and signal the comparison comprises: quantizing the direction value for the time frame with the quantizer according to the bit allocation when the second comparison indicates the direction value for the time frame of the audio object is different from the direction value for the previous time frame of the audio object and set a signal flag to indicate that thedirection value for the time frame differs from the direction value for the previous time frame; and setting a signal flag to indicate that the direction value for the time frame is the same as the direction value for the previous time frame when the second comparison indicates the direction value for the time frame of the audio object is the same as the direction value for the previous time frame of the audio object.

13. The method as claimed in Claims 11 and 12, wherein depending on the first comparison, either quantizing the direction value for the time frame of the audio object with a quantizer according to the bit allocation, or comparing, as a second comparison, the direction value for the time frame of the audio object with a direction value for a previous time frame of the audio object comprises: quantizing the direction value for the time frame of the audio object with a quantizer according to the bit allocation when the bit allocation for the quantization of the direction value is not less than the threshold bit allocation value; and comparing the direction value for the time frame of the audio object with a direction value for a previous time frame of the audio object as the second comparison when the bit allocation for the quantization of the direction value is less than the threshold bit allocation value.

14. The method as claimed in Claims 11 to 13, wherein the quantizer is a spherical grid quantizer wherein the spherical grid is formed by covering the sphere with smaller spheres, wherein the smaller spheres define the points of the spherical grid.

15. The method as claimed in Claims 11 to 14, wherein the direction value comprises an azimuth value and an elevation value.

16. A method comprising: comparing a bit allocation for a direction value index for a time frame of an audio object against a threshold bit allocation value; depending on the comparison, either decoding the direction value index for the time frame of the audio object with a de-quantizer according to the bit allocation,or reading a state of a signal flag associated with the direction value index for the time frame of the audio object; and depending on the state of the signal flag; either setting a quantized direction value for the time frame of the audio object to be a quantized direction value for a previous time frame of the audio object, or decoding the direction value index for the time frame of the audio object with a de-quantizer according to the bit allocation giving a quantized direction value for the time frame of the audio object and adjusting an azimuth value of the quantized direction value for the time frame of the audio object in accordance with a quantization resolution of the azimuth value.

17. The method as claimed in Claim 16, wherein adjusting an azimuth value of the quantized direction value for the time frame of the audio object in accordance with a quantization resolution of the azimuth value comprises: comparing the product of the azimuth value of the quantized direction value for the time frame and an azimuth value of the quantized direction value for the previous time frame of the audio object, and when the product is greater than zero: determining a difference between two consecutive azimuth quantization values of the de-quantizer; when a difference between the azimuth value of the quantized direction value for the time frame and the azimuth value of the quantized direction value for the previous time frame of the audio object is greater than half the difference between two consecutive azimuth quantization values of the de-quantizer subtracting the half difference between two consecutive azimuth quantization values of the de-quantizer from the azimuth value of the quantized direction value for the time frame of the audio object; and when a difference between the azimuth value of the quantized direction value for the previous time frame and the azimuth value of the quantized direction value for the time frame of the audio object is greater than half the difference between two consecutive azimuth quantization values of the de-quantizer adding the half difference between twoconsecutive azimuth quantization values of the de-quantizer to the azimuth value of the quantized direction value for the time frame of the audio object.

18. The method as claimed in Claim 17, wherein determining a difference between two consecutive azimuth quantization values of the de-quantizer comprises: dividing the circumference of a circle by a number of azimuth values, where the number of azimuth values is determined by the elevation value of the quantized direction value for the time frame.

19. The method as claimed in Claims 16 to 18, wherein the state of the signal flag indicates one of: a direction value for the time frame of the audio object differs from a direction value for the previous time frame of the audio object; or a direction value for the time frame of the audio object is the same as a direction value for the previous time frame of the audio object;20. The method as claimed in Claims 16 to 19, wherein the de-quantizer is a spherical grid quantizer wherein the spherical grid is formed by covering the sphere with smaller spheres, wherein the smaller spheres define the points of the spherical grid.

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