Picture encoding device and picture encoding method

1. A picture encoding device that encodes a picture and encodes a difference quantization parameter in a unit of a quantization coding block which is divided from the picture and is a management unit of a quantization parameter, comprising:

a quantization parameter derivation unit that derives a quantization parameter of a first quantization coding block;

a prediction quantization parameter derivation unit that derives a prediction quantization parameter using the quantization parameters of two quantization coding blocks which precede the first quantization coding block in order of encoding;

a difference quantization parameter derivation unit that derives a difference quantization parameter of the first quantization coding block, using a difference between the quantization parameter of the first quantization coding block and the prediction quantization parameter; and

an encoder that encodes the difference quantization parameter,

wherein the prediction quantization parameter derivation unit derives the prediction quantization parameter using two quantization parameters: one quantization parameter of a previous quantization coding block which immediately precedes the first quantization coding block to be encoded in order of encoding and another quantization parameter of a quantization coding block which precedes the previous quantization coding block in order of encoding and is not spatially neighboring the first quantization coding block to be encoded, and

wherein a size of a coding block which is a basic unit of encoding process is set hierarchically.

2. A picture encoding method that encodes a picture and encodes a difference quantization parameter in a unit of a quantization coding block which is divided from the picture and is a management unit of a quantization parameter, comprising:

a quantization parameter derivation step of deriving a quantization parameter of a first quantization coding block;

a prediction quantization parameter derivation step of deriving a prediction quantization parameter using the quantization parameters of two quantization coding blocks which precede the first quantization coding block in order of encoding;

a difference quantization parameter derivation step of deriving a difference quantization parameter of the first quantization coding block, using a difference between the quantization parameter of the first quantization coding block and the prediction quantization parameter; and

an encoding step of encoding the difference quantization parameter,

wherein the prediction quantization parameter derivation step derives the prediction quantization parameter using two quantization parameters: one quantization parameter of a previous quantization coding block which immediately precedes the first quantization coding block to be encoded in order of encoding and another quantization parameter of a quantization coding block which precedes the previous quantization coding block in order of encoding and is not spatially neighboring the first quantization coding block to be encoded, and

wherein a size of a coding block which is a basic unit of encoding process is set hierarchically.

3. A picture decoding device that decodes a picture and decodes a bitstream in which a difference quantization parameter is encoded in a unit of a quantization decoding block which is divided from the picture and is a management unit of a quantization parameter, comprising:

a decoder that decodes the bitstream in the unit of the quantization decoding block and extracts a difference quantization parameter of a first quantization decoding block to be decoded;

a prediction quantization parameter derivation unit that derives a prediction quantization parameter using the quantization parameters of two quantization decoding blocks which precede the first quantization decoding block to be decoded in order of decoding; and

a quantization parameter derivation unit that adds the difference quantization parameter of the first quantization decoding block to be decoded and the prediction quantization parameter to derive the quantization parameter of the first quantization decoding block to be decoded,

wherein the prediction quantization parameter derivation unit derives the prediction quantization parameter using two quantization parameters: one quantization parameter of a previous quantization decoding block which immediately precedes the first quantization decoding block to be decoded in order of decoding and another quantization parameter of a quantization decoding block which precedes the previous quantization decoding block in order of decoding and is not spatially neighboring the first quantization decoding block to be decoded, and

wherein a size of a decoding block which is a basic unit of decoding process is set hierarchically.

4. A picture decoding method that decodes a picture and decodes a bitstream in which a difference quantization parameter is encoded in a unit of a quantization decoding block which is divided from the picture and is a management unit of a quantization parameter, comprising:

a decoding step of decoding the bitstream in the unit of the quantization decoding block and extracting a difference quantization parameter of a first quantization decoding block to be decoded;

a prediction quantization parameter derivation step of deriving a prediction quantization parameter using the quantization parameters of two quantization decoding blocks which precede the first quantization decoding block to be decoded in order of decoding; and

a quantization parameter derivation step of adding the difference quantization parameter of the first quantization decoding block to be decoded and the prediction quantization parameter to derive the quantization parameter of the first quantization decoding block to be decoded,

wherein the prediction quantization parameter derivation step derives the prediction quantization parameter using two quantization parameters: one quantization parameter of a previous quantization decoding block which immediately precedes the first quantization decoding block to be decoded in order of decoding and another quantization parameter of a quantization decoding block which precedes the previous quantization decoding block in order of decoding and is not spatially neighboring the first quantization decoding block to be decoded, and

wherein a size of a decoding block which is a basic unit of decoding process is set hierarchically.