Adaptive loop filter (ALF) coefficients in video coding

A device for coding video data, the device comprising:

• memory configured to store ALF coefficients of a previously coded picture or slice;
• and
• processing circuitry coupled to the memory and configured to:
• determine that temporal prediction for adaptive loop filter (ALF) is enabled for one or more intra coded slices of a picture, wherein to determine that temporal prediction for ALF is enabled, the processing circuitry is configured to determine that temporal prediction for ALF is enabled based on the picture having a temporal index value that is not equal to 0;
• determine ALF coefficients for one or more blocks of the one or more intra coded slices, for which the temporal prediction for ALF is enabled, based on the ALF coefficients of the previously coded picture or slice stored in memory;
• and
• apply the determined ALF coefficients to the one or more blocks to generate one or more filtered blocks.

A non-transitory computer-readable storage medium having instructions stored thereon that when executed cause one or more processors of a device for coding video data to:

• determine that temporal prediction for adaptive loop filter (ALF) is enabled for one or more intra coded slices of a picture, wherein the instructions that cause the one or more processors to determine that temporal prediction for ALF is enabled comprise instructions that cause the one or more processors to determine that temporal prediction for ALF is enabled based on the picture having a temporal index value that is not equal to 0;
• determine ALF coefficients for one or more blocks of the one or more intra coded slices, for which the temporal prediction for ALF is enabled, based on ALF coefficients of a previously coded picture or slice;
• and
• apply the determined ALF coefficients to the one or more blocks to generate one or more filtered blocks.

A device for coding video data, the device comprising:

• means for determining that temporal prediction for adaptive loop filter (ALF) is enabled for one or more intra coded slices of a picture, wherein the means for determining that temporal prediction for ALF is enabled comprises means for determining that temporal prediction for ALF is enabled based on the picture having a temporal index value that is not equal to 0;
• means for determining ALF coefficients for one or more blocks of the one or more intra coded slices, for which the temporal prediction for ALF is enabled, based on ALF coefficients of a previously coded picture or slice;
• and
• means for applying the determined ALF coefficients to the one or more blocks to generate one or more filtered blocks.

A device for decoding video data, the device comprising:

• memory configured to store ALF coefficients of a previously decoded picture or slice;
• and
• processing circuitry coupled to the memory and configured to:
• determine that temporal prediction for adaptive loop filter (ALF) is enabled for one or more intra decoded slices of a picture, wherein to determine that temporal prediction for ALF is enabled, the processing circuitry is configured to determine that temporal prediction for ALF is enabled without determining a slice type of the one or more blocks;
• determine ALF coefficients for one or more blocks of the one or more intra decoded slices, for which the temporal prediction for ALF is enabled, based on the ALF coefficients of the previously decoded picture or slice stored in memory;
• and
• apply the determined ALF coefficients to the one or more blocks to generate one or more filtered blocks.