Constrained Coding Tree for Video Coding

Abstract

A video coding mechanism is disclosed. The mechanism includes partitioning an image to create at least one coding tree unit (CTU) with at least one coding tree node. The mechanism further includes determining that the coding tree node height is twice a maximum transform unit (TU) height and the coding tree node width is twice a maximum TU width. The mechanism further includes selecting a split mode for the coding tree node based on the determination. The split mode is selected from a quad-tree split, a horizontal binary-tree split, and no split. The mechanism further includes applying the split mode to the coding tree node to create one or more coding units (CUs). The mechanism further includes encoding the CUs into a bitstream. The mechanism further includes transmitting the bitstream toward a decoder.

What is claimed is: 
     
         1 . A method implemented in an encoder, the method comprising:
 partitioning, by a processor of the encoder, an image to obtain a coding tree unit (CTU) with a coding tree node;   determining, by the processor, whether a triple tree split for the coding tree node is allowed by determining whether a height of the coding tree node is larger than sixty four, or whether a width of the coding tree node is larger than sixty four, wherein the triple tree split for the coding tree node is not allowed when the coding tree node height is larger than sixty four or when a width of the coding tree node is larger than sixty four;   determining, by the processor, a split mode for the coding tree node based on the determination of whether the triple tree split for the coding tree node is allowed;   applying, by the processor, the split mode to the coding tree node to obtain one or more coding units (CUs);   encoding, by the processor, the CUs into a bitstream.   
     
     
         2 . The method of  claim 1 , further comprising storing, by a memory of the encoder, the bitstream for transmission toward a decoder. 
     
     
         3 . The method of  claim 1 , further comprising signaling the split mode for the coding tree node in the bitstream by encoding a first flag to indicate whether the split mode is a quad-tree split and a second flag to indicate whether the split mode is a horizontal binary-tree split when the triple tree split for the coding tree node is not allowed. 
     
     
         4 . The method of  claim 1 , wherein the CTU is a constrained CTU that prevents creation of a CU covered by more than one pipeline blocks. 
     
     
         5 . A method implemented in an encoder, the method comprising:
 partitioning, by a processor of the encoder, an image to obtain a coding tree unit (CTU) with a coding tree node;   determining, by the processor, to split the coding tree node when a height of the coding tree node is not larger than sixty four and a width of the coding tree node is larger than sixty four;   applying, by the processor, a vertical binary-tree split to the coding tree node to obtain one or more coding units (CUs) when determining to split the coding tree node;   encoding, by the processor, the CUs into a bitstream.   
     
     
         6 . The method of  claim 5 , further comprising storing, by a memory of the encoder, the bitstream for transmission toward a decoder. 
     
     
         7 . The method of  claim 5 , wherein a horizontal binary-tree split, a quad-tree split, a vertical triple-tree split, and a horizontal triple-tree split are not applied to the coding tree node when the height of the coding tree node is not larger than sixty four and the width of the coding tree node is larger than sixty four. 
     
     
         8 . The method of  claim 5 , further comprising signaling a split mode for the coding tree node in the bitstream by encoding a first flag to indicate whether the coding tree node is split. 
     
     
         9 . The method of  claim 5 , wherein the CTU is a constrained CTU that prevents creation of a CU covered by more than one pipeline blocks. 
     
     
         10 . A method implemented in a decoder, the method comprising:
 receiving, by a receiver of the decoder, a bitstream including image data of an image;   partitioning, by a processor of the decoder, the image to obtain a coding tree unit (CTU) with a coding tree node;   determining, by the processor, whether a triple tree split for the coding tree node is allowed by determining whether a height of the coding tree node is larger than sixty four, or whether a width of the coding tree node is larger than sixty four samples, wherein the triple tree split for the coding tree node is not allowed when the coding tree node height is larger than sixty four, or when a width of the coding tree node is larger than sixty four;   parsing, by the processor, the bitstream to determine a split mode for the coding tree node based on the determination of whether the triple tree split for the coding tree node is allowed;   applying, by the processor, the split mode to the coding tree node to obtain one or more coding units (CUs);   generating, by the processor, reconstructed blocks of the CUs based on the bitstream to generate a reconstructed image of the image.   
     
     
         11 . The method of  claim 10 , further comprising forwarding, by the processor, the image toward a display. 
     
     
         12 . The method of  claim 11 , wherein parsing the bitstream to determine the split mode for the coding tree node includes parsing a first flag to determine whether the split mode is a quad-tree split when the triple tree split for the coding tree node is not allowed. 
     
     
         13 . The method of  claim 12 , wherein parsing the bitstream to determine the split mode for the coding tree node further includes parsing a second flag to determine whether the split mode is a horizontal binary-tree split when the first flag indicates that the split mode is not the quad-tree split. 
     
     
         14 . The method of  claim 13 , wherein the CTU is a constrained CTU that prevents creation of a CU covered by more than one pipeline blocks. 
     
     
         15 . A method implemented in a decoder, the method comprising:
 receiving, by a receiver of the decoder, a bitstream including image data of an image;   partitioning, by a processor of the decoder, the image to obtain a coding tree unit (CTU) with a coding tree node;   determining, by the processor, a height of the coding tree node is not larger than sixty four and a width of the coding tree node is larger than sixty four;   applying, by the processor, a vertical binary-tree split to the coding tree node to obtain one or more coding units (CUs); and   generating, by the processor based on the bitstream, a reconstructed image containing reconstructed blocks of the CUs.   
     
     
         16 . The method of  claim 15 , further comprising forwarding, by the processor, the image toward a display. 
     
     
         17 . The method of  claim 15 , wherein a horizontal binary-tree split, a quad-tree split, a vertical triple-tree split, and a horizontal triple-tree split are not applied to the coding tree node when the height of the coding tree node is not larger than sixty four and the width of the coding tree node is larger than sixty four. 
     
     
         18 . The method of  claim 15 , further comprising: parsing the bitstream to determine how the coding tree node is split. 
     
     
         19 . The method of  claim 15 , wherein the CTU is a constrained CTU that prevents creation of a CU covered by more than one pipeline blocks.