Image encoding method and apparatus and image decoding method and apparatus

An image decoding apparatus comprising:

• at least one processor configured to:
• obtain at least one coding unit including a current coding unit by hierarchically splitting a current image;
• determine a code value for a difference quantization parameter for the current coding unit as a first value, when a first flag indicating whether signaling for the difference quantization parameter is to be enabled indicates that the signaling for the difference quantization parameter is enabled and a second flag indicating whether a predefined signaling scheme of the difference quantization parameter is to be used indicates that the predefined signaling scheme of the difference quantization parameter is used and a split flag indicating whether or not to split the current coding unit indicates that the current coding unit is split and a split type of the current coding unit is a ternary split type and a sum of a value resulting from applying log 2 to a width of the current coding unit and a value resulting from applying log 2 to a height of the current coding unit is equal to a value resulting from adding 1 to a value resulting from applying log 2 to an area of a difference quantization parameter signaling unit;
• obtain the difference quantization parameter for the current coding unit based on information about a transform unit of the current coding unit, when the code value for the difference quantization parameter for the current coding unit is equal to the first value;
• obtain a quantization parameter for the current coding unit based on a predicted quantization parameter for the current coding unit and the difference quantization parameter for the current coding unit;
• and
• obtain a reconstructed block of the current coding unit, based on the quantization parameter for the current coding unit,
• wherein the split flag indicates one of a binary split type and the ternary split type when the split flag indicates that the current coding unit is split, and
• wherein the value resulting from applying log 2 to the area of the difference quantization parameter signaling unit is determined based on information obtained from a Picture Parameter Set (PPS).

An image encoding method performed by an apparatus, the method comprising:

• obtaining at least one coding unit including a current coding unit by hierarchically splitting a current image;
• obtaining a difference quantization parameter for the current coding unit, based on a predicted quantization parameter for the current coding unit and a quantization parameter for the current coding unit;
• determining a code value for the difference quantization parameter for the current coding unit as a first value, when a first flag indicating whether signaling for the difference quantization parameter is to be enabled indicates that the signaling for the difference quantization parameter is enabled and a second flag indicating whether a predefined signaling scheme of the difference quantization parameter is to be used indicates that the predefined signaling scheme of the difference quantization parameter is used and a split flag indicating whether or not to split the current coding unit indicates that the current coding unit is split and a split type of the current coding unit is a ternary split type and a sum of a value resulting from applying log 2 to a width of the current coding unit and a value resulting from applying log 2 to a height of the current coding unit is equal to a value resulting from adding 1 to a value resulting from applying log 2 to an area of a difference quantization parameter signaling unit;
• obtaining information about a transform unit of the current coding unit based on the difference quantization parameter for the current coding unit, when the code value for the difference quantization parameter for the current coding unit is equal to the first value;
• and
• encoding the information about the transform unit of the current coding unit,
• wherein the split flag indicates one of a binary split type and the ternary split type when the split flag indicates that the current coding unit is split, and
• wherein the value resulting from applying log 2 to the area of the difference quantization parameter signaling unit is determined based on information obtained from a Picture Parameter Set (PPS).

An image encoding apparatus comprising:

• at least one processor configured to:
• obtain at least one coding unit including a current coding unit by hierarchically splitting a current image;
• obtain a difference quantization parameter for the current coding unit, based on a predicted quantization parameter for the current coding unit and a quantization parameter for the current coding unit;
• determine a code value for the difference quantization parameter for the current coding unit as a first value, when a first flag indicating whether signaling for the difference quantization parameter is to be enabled indicates that the signaling for the difference quantization parameter is enabled and a second flag indicating whether a predefined signaling scheme of the difference quantization parameter is to be used indicates that the predefined signaling scheme of the difference quantization parameter is used and a split flag indicating whether or not to split the current coding unit indicates that the current coding unit is split and a split type of the current coding unit is a ternary split type and a sum of a value resulting from applying log 2 to a width of the current coding unit and a value resulting from applying log 2 to a height of the current coding unit is equal to a value resulting from adding 1 to a value resulting from applying log 2 to an area of a difference quantization parameter signaling unit;
• obtain information about a transform unit of the current coding unit based on the difference quantization parameter for the current coding unit, when the code value for the difference quantization parameter for the current coding unit is equal to the first value;
• and
• encode the information about the transform unit of the current coding unit,
• wherein the split flag indicates one of a binary split type and the ternary split type when the split flag indicates that the current coding unit is split, and
• wherein the value resulting from applying log 2 to the area of the difference quantization parameter signaling unit is determined based on information obtained from a Picture Parameter Set (PPS).