Robust encoding/decoding of escape-coded pixels in palette mode

One or more non-transitory computer-readable media having stored thereon encoded data for a picture, the encoded data including a syntax element that represents a quantized sample value for a color component of a unit of the picture, the unit having been encoded in a lossy manner, the encoded data being organized to facilitate decoding of the picture by operations comprising decoding the unit in a palette mode, including, for an escape mode of the palette mode:

• determining a unit-level quantization parameter for the unit, the unit-level quantization parameter being based at least in part on a picture-level quantization parameter for the picture, a slice-level quantization parameter offset for a slice of the picture, and a unit-level quantization parameter offset for the unit;
• decoding the quantized sample value for the color component of the unit using a kth-order Exponential-Golomb binarization of the syntax element without any parsing dependency on the unit-level quantization parameter for the unit, wherein k is a pre-determined number, the color component of the unit being indicated by a color component index cIdx for the color component, and the quantized sample value for the color component of the unit being constrained by a value equal to (1<<BitDepth)−1, wherein BitDepth represents a sample depth that applies for the color component that is indicated by the color component index cIdx, and wherein the decoding includes:
• determining the kth-order Exponential-Golomb binarization by invoking a kth-order Exponential-Golomb binarization process;
• and
• entropy decoding a string of one or more binary values for the quantized sample value for the color component of the unit, wherein the entropy decoding uses the kth-order Exponential-Golomb binarization;
• and
• inverse quantizing the quantized sample value for the color component of the unit.

A computer system comprising a processor and memory that implement a video decoder system, the video decoder system comprising:

• a buffer, implemented using at least some of the memory, configured to receive encoded data for a picture;
• and
• a video decoder configured to decode the picture with operations that include decoding a unit of the picture in a palette mode, the unit having been encoded in a lossy manner, wherein the decoding the unit in the palette mode includes, for an escape mode of the palette mode:
• determining a unit-level quantization parameter for the unit, the unit-level quantization parameter being based at least in part on a picture-level quantization parameter for the picture, a slice-level quantization parameter offset for a slice of the picture, and a unit-level quantization parameter offset for the unit;
• decoding a quantized sample value for a color component of the unit using a kth-order Exponential-Golomb binarization of a syntax element that represents the quantized sample value for the color component of the unit without any parsing dependency on the unit-level quantization parameter for the unit, wherein k is a pre-determined number, the color component of the unit being indicated by a color component index cIdx for the color component, and the quantized sample value for the color component of the unit being constrained by a value equal to (1<<BitDepth)−1, wherein BitDepth represents a sample depth that applies for the color component that is indicated by the color component index cIdx, and wherein the decoding includes:
• determining the kth-order Exponential-Golomb binarization by invoking a kth-order Exponential-Golomb binarization process;
• and
• entropy decoding a string of one or more binary values for the quantized sample value for the color component of the unit, wherein the entropy decoding uses the kth-order Exponential-Golomb binarization;
• and
• inverse quantizing the quantized sample value for the color component of the unit.