Image encoding device, image encoding method and program, image decoding device, and image decoding method and program

An image decoding device comprising:

• a first decoding unit configured to input a bit stream in which a luminance signal of an image and a chrominance signal of the image are encoded, and to decode a header including a bit depth of the luminance signal and a bit depth of the chrominance signal;
• a second decoding unit configured to decode quantization coefficients;
• a first reconstructing unit configured to reconstruct a luminance quantization parameter used to perform inverse quantization of luminance components of the quantization coefficient;
• a second reconstructing unit configured to reconstruct a chrominance quantization parameter used to perform inverse quantization of chrominance components of the quantization coefficient, the chrominance quantization parameter being a value within a range determined depending on a difference between the bit depth of the luminance signal and the bit depth of the chrominance signal;
• and
• an inverse quantization unit configured to perform inverse quantization of luminance components of the quantization coefficients using the luminance quantization parameter, and to perform inverse quantization of chrominance components of the quantization coefficients using the chrominance quantization parameter.

An image encoding method comprising:

• an input process in which a luminance signal of an image and a chrominance signal of the image are input;
• a first determination process in which a luminance quantization parameter used to quantize the input luminance signal is determined;
• a second determination process in which a chrominance quantization parameter used to quantize the input chrominance signal is determined, the chrominance quantization parameter being a value within a range depending a difference between a bit depth of the input luminance signal and a bit depth of the input chrominance signal;
• and
• a quantizing process in which the input luminance signal is quantized by the luminance quantization parameter, and the input chrominance signal is quantized by the chrominance quantization parameter.

An image decoding method comprising:

• a first decoding process in which a bit stream in which a luminance signal of an image and a chrominance signal of the image are encoded is input, and a header including a bit depth of the luminance signal and a bit depth of the chrominance signal is decoded;
• a second decoding process in which quantization coefficients are decoded;
• a first reconstructing process in which a luminance quantization parameter used to perform inverse quantization of luminance components of the quantization coefficient is reconstructed;
• a second reconstructing process in which a chrominance quantization parameter used to perform inverse quantization of chrominance components of the quantization coefficient is reconstructed, the chrominance quantization parameter being a value within a range determined depending on a difference between the bit depth of the luminance signal and the bit depth of the chrominance signal;
• and
• an inverse quantization process in which luminance components of the quantization coefficients are subjected to inverse quantization using the luminance quantization parameter, and in which chrominance components of the quantization coefficients are subjected to inverse quantization using the chrominance quantization parameter.

A non-transitory computer-readable storage medium storing a computer program for causing a computer to execute a method comprising;

• an input process in which a luminance signal of an image and a chrominance signal of the image are input;
• a first determination process in which a luminance quantization parameter used to quantize the input luminance signal is determined;
• a second determination process in which a chrominance quantization parameter used to quantize the input chrominance signal is determined, the chrominance quantization parameter being a value within a range depending a difference between a bit depth of the input luminance signal and a bit depth of the input chrominance signal;
• and
• a quantizing process in which the input luminance signal is quantized by the luminance quantization parameter, and the input chrominance signal is quantized by the chrominance quantization parameter.

A non-transitory computer-readable storage medium storing a computer program for causing a computer to execute a method comprising;

• a first decoding process in which a bit stream in which a luminance signal of an image and a chrominance signal of the image are encoded is input, and a header including a bit depth of the luminance signal and a bit depth of the chrominance signal is decoded;
• a second decoding process in which quantization coefficients are decoded;
• a first reconstructing process in which a luminance quantization parameter used to perform inverse quantization of luminance components of the quantization coefficient is reconstructed;
• a second reconstructing process in which a chrominance quantization parameter used to perform inverse quantization of chrominance components of the quantization coefficient is reconstructed, the chrominance quantization parameter being a value within a range determined depending on a difference between the bit depth of the luminance signal and the bit depth of the chrominance signal;
• and
• an inverse quantization process in which luminance components of the quantization coefficients are subjected to inverse quantization using the luminance quantization parameter, and in which chrominance components of the quantization coefficients are subjected to inverse quantization using the chrominance quantization parameter.