Quantization parameter (QP) coding in video coding

A method of encoding video data, the method comprising:

• determining that a current block of video data is to be encoded using a lossless coding mode;
• determining that the current block of video data is a current quantization block based on a size of the current block of video data;
• determining a quantization parameter (QP) value for the current quantization block of video data based on a zero value for a delta quantization parameter (dQP) for the current quantization block and a value of a QP predictor, wherein the dQP value is a difference between the QP value and the value of the QP Predictor;
• generating a lossless coding syntax element for the current block of video data, the lossless coding syntax element indicating that the current block of video data is encoded using a lossless coding mode, the lossless coding syntax element being separate from the QP value;
• and
• encoding the current quantization block according to the lossless coding mode and the determined QP value.

An apparatus configured to decode video data, the apparatus comprising:

• a memory configured to store the video data;
• and
• a video decoder configured to:
• receive a lossless coding syntax element for a current block of the video data, the lossless coding syntax element indicating that the current block of the video data is encoded using a lossless coding mode, the lossless coding syntax element being separate from a quantization parameter (QP) value;
• determine that the current block of the video data is a current quantization block based on a size of the current block of the video data;
• assign a delta quantization parameter (dQP) value of zero for the current quantization block, wherein the dQP value is a difference between the QP value and a value of a QP Predictor;
• determine the QP value for the current quantization block based on the assigned dQP value and a QP Predictor;
• and
• decode the current quantization block according to the lossless coding mode and the determined QP value.

An apparatus configured to encode video data, the apparatus comprising:

• a memory configured to store the video data;
• and
• a video encoder configured to:
• determine that a current block of the video data is to be encoded using a lossless coding mode;
• determine that the current block of the video data is a current quantization block based on a size of the current block of the video data;
• determine a quantization parameter (QP) value for the current quantization block of the video data based on a zero value for a delta quantization parameter (dQP) for the current quantization block and a value of a QP predictor, wherein the dQP value is a difference between the QP value and the value of the QP Predictor;
• generate a lossless coding syntax element for the current block of the video data, the lossless coding syntax element indicating that the current block of the video data is encoded using a lossless coding mode, the lossless coding syntax element being separate from the QP value;
• and
• encode the current quantization block according to the lossless coding mode and the determined QP value.

An apparatus configured to decode video data, the apparatus comprising:

• means for receiving a lossless coding syntax element for a current block of video data, the lossless coding syntax element indicating that the current block of video data is encoded using a lossless coding mode, the lossless coding syntax element being separate from a quantization parameter (QP) value;
• means for determining that the current block of video data is a current quantization block based on a size of the current block of video data;
• means for assigning a delta quantization parameter (dQP) value of zero for the current quantization block, wherein the dQP value is a difference between the QP value and a value of a QP Predictor;
• means for determining the QP value for the current quantization block based on the assigned dQP value and a QP Predictor;
• and
• means for decoding the current quantization block according to the lossless coding mode and the determined QP value.

An apparatus configured to encode video data, the apparatus comprising:

• means for determining that a current block of video data is to be encoded using a lossless coding mode;
• means for determining that the current block of video data is a current quantization block based on a size of the current block of video data;
• means for determining a quantization parameter (QP) value for the current quantization block of video data based on a zero value for a delta quantization parameter (dQP) for the current quantization block and a value of a QP predictor, wherein the dQP value is a difference between the QP value and the value of the QP Predictor;
• means for generating a lossless coding syntax element for the current block of video data, the lossless coding syntax element indicating that the current block of video data is encoded using a lossless coding mode, the lossless coding syntax element being separate from the QP value;
• and
• means for encoding the current quantization block according to the lossless coding mode and the determined QP value.

A non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors of a device configured to decode video data to:

• receive a lossless coding syntax element for a current block of video data, the lossless coding syntax element indicating that the current block of video data is encoded using a lossless coding mode, the lossless coding syntax element being separate from a quantization parameter (QP) value;
• determine that the current block of video data is a current quantization block based on a size of the current block of video data;
• assign a delta quantization parameter (dQP) value of zero for the current quantization block, wherein the dQP value is a difference between the QP value and a value of a QP Predictor;
• determine the QP value for the current quantization block based on the assigned dQP value and a QP Predictor;
• and
• decode the current quantization block according to the lossless coding mode and the determined QP value.

A non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors of a device configured to encode video data to:

• determine that a current block of video data is to be encoded using a lossless coding mode;
• determine that the current block of video data is a current quantization block based on a size of the current block of video data;
• determine a quantization parameter (QP) value for the current quantization block of video data based on a zero value for a delta quantization parameter (dQP) for the current quantization block and a value of a QP predictor, wherein the dQP value is a difference between the QP value and the value of the QP Predictor;
• generate a lossless coding syntax element for the current block of video data, the lossless coding syntax element indicating that the current block of video data is encoded using a lossless coding mode, the lossless coding syntax element being separate from the QP value;
• and
• encode the current quantization block according to the lossless coding mode and the determined QP value.