Methods and apparatus for determining quantization parameter predictors from a plurality of neighboring quantization parameters

An apparatus, comprising:

• a memory and a processor, configured to:
• decode image data in at least a current portion of a picture using a quantization parameter predictor for a current quantization parameter to be applied to the current portion, the quantization parameter predictor based on a mean, wherein the mean is a mean of a first quantization parameter of a previously decoded neighboring portion to the left of the current portion and a second quantization parameter of a previously decoded neighboring portion above the current portion when the neighboring portion to the left and the neighboring portion above are both available,
• wherein if both of the first quantization parameter and the second quantization parameter are unavailable due to their respective neighboring portion being unavailable, then both are replaced with a slice level quantization parameter in the mean;
• decode from a bitstream a value indicative of a difference between the current quantization parameter and the quantization parameter predictor;
• and,
• decode image data using said value indicative of a difference between the current quantization parameter and the quantization parameter predictor and said quantization parameter predictor.

A method, comprising:

• encoding image data in at least a current portion of a picture using a quantization parameter predictor for a current quantization parameter to be applied to the current portion, the quantization parameter predictor based on a mean,
• wherein the mean is a mean of a first quantization parameter of a previously coded neighboring portion to the left of the current portion and a second quantization parameter of a previously coded neighboring portion above the current portion when the neighboring portion to the left and the neighboring portion above are both available, and
• if both of the first quantization parameter and the second quantization parameter are unavailable due to their respective neighboring portion being unavailable, then both are replaced with a slice level quantization parameter in the mean;
• and
• signaling in a bitstream a value indicative of a difference between the current quantization parameter and the quantization parameter predictor.

A method, comprising:

• decoding image data in at least a current portion of a picture using a quantization parameter predictor for a current quantization parameter to be applied to the current portion, the quantization parameter predictor based on a mean, wherein the mean is a mean of a first quantization parameter of a previously decoded neighboring portion to the left of the current portion and a second quantization parameter of a previously decoded neighboring portion above the current portion when the neighboring portion to the left and the neighboring portion above are both available,
• wherein if both of the first quantization parameter and the second quantization parameter are unavailable due to their respective neighboring portion being unavailable, then both are replaced with a slice level quantization parameter in the mean;
• decoding from a bitstream a value indicative of a difference between the current quantization parameter and the quantization parameter predictor;
• and,
• decoding image data using said value indicative of a difference between the current quantization parameter and the quantization parameter predictor and said quantization parameter predictor.

A non-transitory computer readable storage media having instructions for encoding video signal data encoded thereupon, comprising:

• encoding image data in at least a current portion of a picture using a quantization parameter predictor for a current quantization parameter to be applied to the current portion, the quantization parameter predictor based on a mean,
• wherein the mean is a mean of a first quantization parameter of a previously coded neighboring portion to the left of the current portion and a second quantization parameter of a previously coded neighboring portion above the current portion when the neighboring portion to the left and the neighboring portion above are both available, and
• if both of the first quantization parameter and the second quantization parameter are unavailable due to their respective neighboring portion being unavailable, then both are replaced with a slice level quantization parameter in the mean;
• and
• signalling in a bitstream a value indicative of a difference between the current quantization parameter and the quantization parameter predictor.