Method and device for arithmetic encoding or arithmetic decoding

• US 10,848,180 B2
• Filed: 11/07/2019
• Issued: 11/24/2020
• Est. Priority Date: 10/09/2009
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Wuebbolt, Oliver
• Primary Examiner(s): Beck, Leron
• Application Number:
  US16/677,539
• Publication Number:
  US 20200076450A1
• Time in Patent Office: 383 Days
• Field of Search: 37524001- 29
• CPC Class Codes: H03M 7/4006 Conversion to or from arithmetic code
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/182 the unit being a pixel

Abstract

The invention proposes a method and a device for arithmetic encoding of a current spectral coefficient using preceding spectral coefficients. Said preceding spectral coefficients are already encoded and both, said preceding and current spectral coefficients, are comprised in one or more quantized spectra resulting from quantizing time-frequency-transform of video, audio or speech signal sample values.

Said method comprises processing the preceding spectral coefficients, using the processed preceding spectral coefficients for determining a context class being one of at least two different context classes, using the determined context class and a mapping from the at least two different context classes to at least two different probability density functions for determining the probability density function, and arithmetic encoding the current spectral coefficient based on the determined probability density function wherein processing the preceding spectral coefficients comprises non-uniformly quantizing absolutes of the preceding spectral coefficients for use in determining of the context class.

Claims

1. A method for arithmetic decoding of a current spectral coefficient, the method comprising:

determining a context state based on preceding spectral coefficients, wherein the context state is determined from at least two different context states, and wherein the context state is based on a sum of quantized absolutes of the preceding spectral coefficients;

receiving a reset signal, wherein, in response to the reset signal, only preceding spectral coefficients of current frame are used to determine the context state;

determining a probability density function based on the context state and a mapping from the at least two different context states to at least two different probability density functions; and

arithmetic decoding the current spectral coefficient based on the probability density function.

2. The method of claim 1, wherein processing the preceding spectral coefficients comprises a first quantizing step in which the absolutes of the processed preceding spectral coefficients are quantized according a first quantization scheme, a step of determining a variance of the absolutes of the processed preceding spectral coefficients quantized according the first quantization scheme, a step of using determined variance for selecting one of at least two different nonlinear second quantization schemes, and a second quantizing step in which the absolutes of the processed preceding spectral coefficients quantized according the first quantization scheme are further quantized according to a selected nonlinear second quantization scheme.

3. The method of claim 2, wherein the step of determining the variance of the absolutes of the processed preceding spectral coefficients quantized according the first quantization scheme comprises determining a sum of the absolutes of the processed preceding spectral coefficients quantized according the first quantization scheme and comparing the sum with at least one threshold.

4. A non-transitory storage medium for arithmetic decoding according to the method of claim 1.

5. An apparatus for arithmetic decoding of a current spectral coefficient, the apparatus comprising:

a context classifier configured to determine a context state based on preceding spectral coefficients, wherein the context state is determined from at least two different context states, and wherein the context state is based on a sum of quantized absolutes of the preceding spectral coefficients,

a receiver for receiving a reset signal, wherein the context classifier, in response to the reset signal, uses only preceding spectral coefficients of current frame to determine the context class;

a probability density module configured to determine a probability density function, said probability density module being adapted to use a determined context state and a mapping from the at least two different context states to at least two different probability density functions to determine the probability density function;

and an arithmetic decoder configured to arithmetically decode the current spectral coefficient based on the probability density function.

6. The apparatus of claim 5, wherein a processor is configured to process the preceding spectral coefficients by quantizing absolutes of the preceding spectral coefficients according a first quantization scheme, determining a variance of the absolutes of the preceding spectral coefficients quantized according the first quantization scheme, using a determined variance for selecting one of at least two different nonlinear second quantization schemes, and further quantizing the absolutes of the preceding spectral coefficients quantized according the first quantization scheme according to a selected nonlinear second quantization scheme.

7. The apparatus of claim 6, wherein the processor is configured to determine the variance of the absolutes of the preceding spectral coefficients quantized according the first quantization scheme by determining a sum of the absolutes of the preceding spectral coefficients quantized according the first quantization scheme and comparing a determined sum with at least one threshold.