Model parameter derivation of local illumination compensation in the luma mapping with chroma scaling-mapped domain in video coding

Abstract

An example device for decoding video data includes memory configured to store the video data and one or more processors implemented in circuitry and communicatively coupled to the memory. The one or more processors are configured to reshape a pixel domain reference template block using a forward mapping function into a mapped domain reference template block and derive local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain neighboring reconstruction template block. The one or more processors are configured to apply the LIC model parameters to motion-compensated prediction signals and decode the video data based on the application of the LIC model parameters.

What is claimed is: 
     
         1 . A method of decoding video data, the method comprising:
 reshaping a pixel domain reference template block using a forward mapping function into a mapped domain reference template block;   deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain neighboring reconstruction template block;   applying the LIC model parameters to motion-compensated prediction signals; and   decoding the video data based on the application of the LIC model parameters.   
     
     
         2 . The method of  claim 1 , wherein applying the LIC model parameters further comprises applying an integer shift to the motion-compensated prediction signals. 
     
     
         3 . The method of  claim 2 , wherein the integer shift is a right shift by 6. 
     
     
         4 . The method of  claim 1 , wherein the motion-compensated prediction signals are in a pixel domain. 
     
     
         5 . The method of  claim 1 , wherein the motion-compensated prediction signals are in a mapped domain. 
     
     
         6 . The method of  claim 1 , wherein the forward mapping function comprises:
   FwdMap( Y _pred)=(( b 2− b 1)/( a 2− a 1))*( Y _pred− a 1)+ b 1,
   
       where Y_pred is a luma prediction signal, i is a piece index, a1 is an input pivot point of i, a2 is an input pivot point of i+1, b1 is a mapped pivot point of i, and b2 is a mapped pivot point of i+1. 
     
     
         7 . The method of  claim 1 , wherein the forward mapping function comprises a gamma function. 
     
     
         8 . The method of  claim 7 , wherein the gamma function comprises:
   FwdMap( x )= A*xr,      
       where A and r are constant values. 
     
     
         9 . The method of  claim 1 , wherein the forward mapping function comprises a polynomial function. 
     
     
         10 . The method of  claim 9 , wherein the polynomial function comprises FwdMap(x)=Σi∈{0, 1, . . . , n} a i x i , where a i  represents a real number which is a coefficient of the polynomial function of x. 
     
     
         11 . The method of  claim 1 , wherein the LIC model parameters are applied on a coding unit (CU) basis. 
     
     
         12 . The method of  claim 11 , further comprising:
 determining that luma mapping with chroma scaling is enabled for the CU.   
     
     
         13 . A device for decoding video data, the device comprising:
 memory configured to store the video data; and   one or more processors implemented in circuitry and communicatively coupled to the memory, the one or more processors being configured to:
 reshape a pixel domain reference template block using a forward mapping function into a mapped domain reference template block; 
 derive local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain neighboring reconstruction template block; 
 apply the LIC model parameters to motion-compensated prediction signals; and 
 decode the video data based on the application of the LIC model parameters. 
   
     
     
         14 . The device of  claim 13 , wherein as part of applying the LIC model parameters, the one or more processors are further configured to:
 apply an integer shift to the motion-compensated prediction signals.   
     
     
         15 . The device of  claim 14 , wherein the integer shift is a right shift by 6. 
     
     
         16 . The device of  claim 13 , wherein the motion-compensated prediction signals are in a pixel domain. 
     
     
         17 . The device of  claim 13 , wherein the motion-compensated prediction signals are in a mapped domain. 
     
     
         18 . The device of  claim 13 , wherein the forward mapping function comprises:
   FwdMap( Y _pred)=(( b 2− b 1)/( a 2− a 1))*( Y _pred− a 1)+ b 1,
   
       where Y_pred is a luma prediction signal, i is a piece index, a1 is an input pivot point of a2 is an input pivot point of i+1, b1 is a mapped pivot point of i, and b2 is a mapped pivot point of i+1. 
     
     
         19 . The device of  claim 13 , wherein the forward mapping function comprises a gamma function. 
     
     
         20 . The device of  claim 19 , wherein the gamma function comprises:
   FwdMap( x )= A*xr,      
       where A and r are constant values. 
     
     
         21 . The device of  claim 13 , wherein the forward mapping function comprises a polynomial function. 
     
     
         22 . The device of  claim 21 , wherein the polynomial function comprises:
   FwdMap( x )=Σ i∈{ 0,1, . . . , n}a   i   x   i ,
   
       where a i  represents a real number which is a coefficient of the polynomial function of x. 
     
     
         23 . The device of  claim 13 , wherein the one or more processors apply the LIC model parameters on a coding unit (CU) basis. 
     
     
         24 . The device of  claim 23 , wherein the one or more processors are further configured to:
 determine that luma mapping with chroma scaling is enabled for the CU.   
     
     
         25 . The device of  claim 13 , further comprising:
 a display configured to display the video data.   
     
     
         26 . The device of  claim 13 , further comprising:
 a camera configured to capture the video data.   
     
     
         27 . The device of  claim 13 , wherein the device comprises a mobile telephone. 
     
     
         28 . A non-transitory computer readable storage medium having instructions stored thereon which, when executed, cause one or more processors to:
 reshape a pixel domain reference template block using a forward mapping function into a mapped domain reference template block;   derive local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain neighboring reconstruction template block;   apply the LIC model parameters to motion-compensated prediction signals; and   decode the video data based on the application of the LIC model parameters.   
     
     
         29 . A device for decoding video data, the device comprising:
 means for reshaping a pixel domain reference template block using a forward mapping function into a mapped domain reference template block;   means for deriving local illumination compensation (LIC) model parameters from the mapped domain reference template block and a mapped domain neighboring reconstruction template block;   means for applying the LIC model parameters to motion-compensated prediction signals; and   means for decoding the video data based on the application of the LIC model parameters.