Parallel CABAC Decoding Using Entropy Slices

Abstract

A method of video encoding is provided that includes performing context-adaptive binary arithmetic coding (CABAC) on a plurality of syntax element values in a slice to generate a plurality of entropy-encoded syntax element values, generating an entropy slice header to identify the plurality of entropy-encoded syntax element values as an entropy slice, wherein the entropy slice header comprises context model initialization information, and outputting the entropy slice header and the plurality of entropy encoded syntax element values.

1 . A method of video encoding comprising:
 performing context-adaptive binary arithmetic coding (CABAC) on a plurality of syntax element values in a slice to generate a plurality of entropy-encoded syntax element values;   generating an entropy slice header to identify the plurality of entropy-encoded syntax element values as an entropy slice, wherein the entropy slice header comprises context model initialization information; and   outputting the entropy slice header and the plurality of entropy encoded syntax element values.   
   
   
       2 . The method of  claim 1 , wherein the context model initialization information comprises values for setting an initial state of a selected context model. 
   
   
       3 . The method of  claim 1 , wherein the context model initialization information comprises values for setting an initial state of each of a subset of context models selected from a plurality of context models. 
   
   
       4 . The method of  claim 3 , wherein at least one context model included in the subset is empirically selected. 
   
   
       5 . The method of  claim 3 , wherein at least one context model in the subset is dynamically selected based on use of the context model during the CABAC coding of the plurality of syntax element values. 
   
   
       6 . The method of  claim 5 , wherein a context index of the at least one context model in the subset is comprised in the entropy slice header. 
   
   
       7 . The method of  claim 3 , wherein at least one context model in the subset is selected based on a type of the slice. 
   
   
       8 . The method of  claim 3 , wherein generating an entropy slice header comprises compressing the values. 
   
   
       9 . A method of video decoding comprising:
 identifying a plurality of entropy slice headers in a slice; and   decoding entropy slices corresponding to the plurality of entropy slice headers in parallel, wherein each entropy slice comprises a plurality of entropy-encoded syntax element values encoded using context-adaptive binary arithmetic coding (CABAC), and wherein decoding each entropy slice comprises:
 initializing a context model of a plurality of context models using context model initialization information comprised in the entropy slice header corresponding to the entropy slice; 
 decoding the plurality of entropy-encoded syntax element values comprised in the entropy slice to generate a plurality of syntax element values, wherein the initialized context model is used; and 
 outputting the plurality of syntax element values. 
   
   
   
       10 . The method of  claim 9 , wherein the context model initialization information comprises values for setting an initial state of each of a subset of context models selected from the plurality of context models. 
   
   
       11 . The method of  claim 10 , wherein at least one context model included in the subset was empirically selected. 
   
   
       12 . The method of  claim 10 , wherein at least one context model in the subset was dynamically selected based on use of the context model during the CABAC encoding of the plurality of syntax element values. 
   
   
       13 . The method of  claim 12 , wherein a context index of the at least one context model in the subset is comprised in the entropy slice header in the entropy slice header corresponding to the entropy slice. 
   
   
       14 . The method of  claim 10 , wherein at least one context model in the subset was selected based on a type of the slice. 
   
   
       15 . The method of  claim 9 , further comprising decompressing the context model initialization information. 
   
   
       16 . A method for video decoding comprising:
 identifying a plurality of entropy slice headers in a slice; and   decoding entropy slices corresponding to the plurality of entropy slice headers in parallel, wherein each entropy slice comprises a plurality of entropy-encoded syntax element values encoded using context-adaptive binary arithmetic coding (CABAC), and wherein decoding each entropy slice comprises:
 estimating context model initialization information for a context model of a plurality of context models based on decoding of a reference entropy slice subset; 
 initializing the context model using the estimated context model initialization information; 
 decoding the plurality of entropy-encoded syntax element values comprised in the entropy slice to generate a plurality of syntax element values, wherein the initialized context model is used; and 
 outputting the plurality of syntax element values. 
   
   
   
       17 . The method of  claim 16 , wherein the reference entropy slice subset is identified in the entropy slice header corresponding to the entropy slice. 
   
   
       18 . The method of  claim 16 , wherein the reference entropy slice subset comprises at least one of M sequential entropy slices decoded prior to decoding the entropy slice, wherein M is a maximum number of entropy slices that can be decoded in parallel. 
   
   
       19 . The method of  claim 18 , wherein the value of M is set by a video encoder that generates the plurality of entropy slices.