Method and apparatus for adaptively encoding and decoding a quantization parameter based on a quadtree structure

Abstract

Disclosed are an apparatus and a method of encoding/decoding a video, particularly a method and an apparatus for storing a quantization parameter differential value in a largest coding unit (LCU) based on quadtree splitting and adaptively predicting a quantization parameter value based on context information on neighboring CUs. Quadtree-based quantization parameter encoding and decoding methods and apparatuses effectively show information on a block having a quantization parameter differential value based on splitting information on a CU and adaptively predict a quantization parameter value using context information including a block size, block partition and a quantization parameter of a neighboring CU.

The invention claimed is: 
     
       1. A method for decoding a video by a decoding apparatus using derivation of a dequantization parameter, the method comprising:
 determining a parameter recorded unit for which dequantization parameter information is signaled, wherein the parameter recorded unit is split in a quadtree structure;   determining a parameter prediction unit used for deriving a predicted dequantization parameter, wherein the parameter prediction unit comprises the parameter recorded unit;   deriving the predicted dequantization parameter for the parameter prediction unit, wherein the predicted dequantization parameter is derived using an average value of dequantization parameters of a block neighboring to a left of the parameter prediction unit and a block neighboring above the parameter prediction unit;   deriving a differential dequantization parameter for the parameter recorded unit based on the dequantization parameter information;   deriving the dequantization parameter using a sum of the predicted dequantization parameter and the differential dequantization parameter; and   performing dequantization using the dequantization parameter.   
     
     
       2. The method of  claim 1 , wherein the parameter prediction unit is a block which has a size same with one of a coding unit size from size of smallest coding unit to size of largest coding unit when a quantization parameter flag has a value of true, and
 wherein the quantization parameter flag indicates whether information with which the dequantization parameter is predicted for coding unit is present or not.   
     
     
       3. The method of  claim 1 , wherein splitting information is a split flag, and
 wherein the parameter recorded unit is split into blocks of lower depth in a quadtree structure when the split flag is equal to 1, and the parameter recorded unit is not split further when the split flag is equal to 0.   
     
     
       4. The method of  claim 1 , wherein splitting information is a split flag,
 wherein the split flag equal to 0 indicates that the differential dequantization parameter is signaled for the parameter recorded unit and the split flag equal to 1 indicates that the parameter recorded unit is split into sub-blocks and the differential dequantization parameter is not signaled for the parameter recorded unit, and   wherein split flags for the sub-blocks are signaled when the split flag is equal to 1.   
     
     
       5. A method for decoding a video by a decoding apparatus using derivation of a dequantization parameter, the method comprising:
 determining a unit image block for parameter recording for which dequantization parameter information is signaled, wherein the unit image block for parameter recording is split in a quadtree structure;   determining a unit image block for parameter predicting, used for deriving a predicted dequantization parameter, wherein the unit image block for parameter predicting comprises the unit image block for parameter recording;   deriving the predicted dequantization parameter for the unit image block for parameter predicting, wherein the predicted dequantization parameter is derived using dequantization parameters of a plurality of blocks neighboring to the unit image block for parameter predicting;   deriving a differential dequantization parameter for the unit image block for parameter recording based on the dequantization parameter information;   deriving the dequantization parameter using a sum of the predicted dequantization parameter and the differential dequantization parameter; and   performing dequantization using the dequantization parameter.   
     
     
       6. The method of claim 5,
 wherein the unit image block for parameter predicting is a block which has a size same with one of a coding unit size from a size of a smallest coding unit to a size of a largest coding unit when a quantization parameter flag has a value of true, and   wherein the quantization parameter flag indicates whether information with which the dequantization parameter is predicted for a coding unit is present or not.   
     
     
       7. A method for encoding a video by an encoding apparatus using encoding of a dequantization parameter, the method comprising:
 determining a parameter recorded unit for which dequantization parameter information is signaled, wherein the parameter recorded unit is split in a quadtree structure;   determining a parameter prediction unit used for deriving a predicted dequantization parameter, wherein the parameter prediction unit comprises the parameter recorded unit;   deriving the predicted dequantization parameter for the parameter prediction unit, wherein the predicted dequantization parameter is derived using dequantization parameters of a block neighboring to a left of the parameter prediction unit and a block neighboring above the parameter prediction unit;   deriving a differential dequantization parameter for the parameter recorded unit by subtracting the predicted dequantization parameter from a dequantization parameter for the parameter recorded unit; and   encoding the differential dequantization parameter as the dequantization parameter information for the parameter recorded unit,   wherein the quadtree structure splits a block into four sub-blocks with half horizontal size.   
     
     
       8. The method of claim 7,
 wherein the parameter prediction unit is a block which has a size same with one of a coding unit size from a size of a smallest coding unit to a size of a largest coding unit when a quantization parameter flag has a value of true, and   wherein the quantization parameter flag indicates whether information with which the dequantization parameter is predicted for a coding unit is present or not.   
     
     
       9. A method for transmitting a bitstream generated by an encoding method performed by an encoding apparatus, the encoding method comprising:
 determining a unit image block for parameter recording for which dequantization parameter information is signaled, wherein the unit image block for parameter recording is split in a quadtree structure;   determining a unit image block for parameter predicting used for deriving a predicted dequantization parameter, wherein the unit image block for parameter predicting comprises the unit image block for parameter recording;   deriving the predicted dequantization parameter for the unit image block for parameter predicting, wherein the predicted dequantization parameter is derived using dequantization parameters of a plurality of blocks neighboring to the unit image block for parameter predicting;   deriving a differential dequantization parameter for the unit image block for parameter recording by subtracting the predicted dequantization parameter from a dequantization parameter for the unit image block for parameter recording; and   encoding the differential dequantization parameter as the dequantization parameter information for the unit image block for parameter recording.   
     
     
       10. The method of claim 9,
 wherein the unit image block for parameter predicting is a block which has a size same with one of a coding unit size from a size of a smallest coding unit to a size of a largest coding unit when a quantization parameter flag has a value of true, and   wherein the quantization parameter flag indicates whether information with which the de quantization parameter is predicted for a coding unit is present or not.