History-based rice parameter derivations for wavefront parallel processing in video coding

A processing device, comprising:

• a memory configured to store a computer program;
• and
• a processor:
• wherein the processor is configured to execute the computer program stored on the memory to:
• access a binary string representing a partition of a video, the partition comprising a plurality of coding tree units (CTUs) forming one or more CTU rows;
• for each CTU of the plurality of CTUs in the partition,
• prior to decoding the CTU, determine that the CTU is the first CTU of a current CTU row among the one or more CTU rows in the partition;
• in response to determining that the CTU is the first CTU of the current CTU row in the partition, set a history counter for a color component for calculating Rice parameters to an initial value;
• decode the CTU, comprising:
• calculating the Rice parameters for transform units (TUs) in the CTU based on the history counter;
• decoding the binary string corresponding to the TUs in the CTU into coefficient values of the TUs based on the calculated Rice parameters;
• and
• determining pixel values for the TUs in the CTU from the coefficient values;
• and
• output a decoded partition of the video comprising the decoded plurality of CTUs in the partition,
• wherein the processor is further configured to, when setting the history counter for a color component cIdx for calculating Rice parameters to an initial value, execute the computer program to perform one or more of following operations:
• in response to determining that a history-based Rice parameter derivation is enabled, calculating the initial value by
• StatCoeff[cIdx]=2*Floor(Log 2(BitDepth−10),
• wherein StatCoeff denotes the history counter, BitDepth specifies a bit depth of samples of luma and chroma arrays of the video, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.

A method for encoding a video, the method comprising:

• accessing a partition of the video, the partition comprising a plurality of coding tree units (CTUs) forming one or more CTU rows;
• processing the partition of the video to generate a binary representation of the partition, the processing comprising:
• for each CTU of the plurality of CTUs in the partition,
• prior to encoding the CTU, determining that parallel coding is enabled and that the CTU is the first CTU of a current CTU row among the one or more CTU rows in the partition;
• in response to determining that the parallel coding is enabled and that the CTU is the first CTU of the current CTU row in the partition, setting a history counter for a color component for calculating Rice parameters to an initial value;
• and
• encoding the CTU, comprising:
• calculating the Rice parameters for transform units (TUs) in the CTU based on the history counter, and
• encoding coefficient values of the TUs into a binary representation corresponding to the TUs in the CTU based on the calculated Rice parameters;
• and
• encoding the binary representation of the partition into a bitstream of the video,
• wherein setting the history counter for a color component cIdx for calculating Rice parameters to an initial value comprises:
• in response to determining that a history-based Rice parameter derivation is enabled, calculating the initial value by
• StatCoeff[cIdx]=2*Floor(Log 2(BitDepth−10),
• wherein StatCoeff denotes the history counter, BitDepth specifies a bit depth of samples of luma and chroma arrays of the video, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.

A processing device, comprising:

• a memory configured to store a computer program and a bitstream;
• and
• a processor:
• wherein the processor is configured to execute the computer program stored on the memory to perform the following steps for generating the bitstream:
• accessing a partition of a video, the partition comprising a plurality of coding tree units (CTUs) forming one or more CTU rows;
• processing the partition of the video to generate a binary representation of the partition, the processing comprising:
• for each CTU of the plurality of CTUs in the partition,
• prior to encoding the CTU, determining that parallel coding is enabled and that the CTU is the first CTU of a current CTU row among the one or more CTU rows in the partition;
• in response to determining that the parallel coding is enabled and that the CTU is the first CTU of the current CTU row in the partition, setting a history counter for a color component for calculating Rice parameters to an initial value;
• and
• encoding the CTU, comprising:
• calculating the Rice parameters for transform units (TUs) in the CTU based on the history counter, and
• encoding coefficient values of the TUs into a binary representation corresponding to the TUs in the CTU based on the calculated Rice parameters, and
• encoding the binary representation of the partition into the bitstream,
• wherein the processor is further configured to, when setting the history counter for a color component cIdx for calculating Rice parameters to an initial value, execute the computer program to perform the following steps for generating the bitstream;
• in response to determining that a history-based Rice parameter derivation is enabled, calculating the initial value by
• StatCoeff[cIdx]=2*Floor(Log 2)BitDepth−10)),
• wherein StatCoeff denotes the history counter, BitDepth specifies a bit depth of samples of luma and chroma arrays of the video, Floor(x) represents the largest integer less than or equal to x, and Log 2(x) is base-2 logarithm of x.