ADAPTIVE QUANTIZATION METHOD FOR 360-DEGREE VIDEO CODING
Systems, procedures, and instrumentalities may be provided for adaptively adjusting quantization parameters (QPs) for 360-degree video coding. For example, a first luma QP for a first region may be identified. Based on the first luma QP, a first chroma QP for the first region may be determined. A QP offset for a second region may be identified. A second luma QP for the second region may be determined based on the first luma QP and/or the QP offset for the second region. A second chroma QP of the second region may be determined based on the first chroma QP and/or the QP offset for the second region. An inverse quantization may be performed for the second region based on the second luma QP for the second region and/or the second chroma QP for the second region. The QP offset may be adapted based on a spherical sampling density.
1 . A method of decoding 360-degree video, comprising:
identifying a first luma quantization parameter (QP) associated with a first region;
determining, based on the first luma QP, a first chroma QP associated with the first region;
identifying a QP offset associated with a second region;
determining a second luma QP of the second region based on the first luma QP and the QP offset associated with the second region;
determining a second chroma QP of the second region based on the first chroma QP and the QP offset associated with the second region; and
performing an inverse quantization for the second region based on the second luma QP of the second region and the second chroma QP of the second region.
2 . The method of claim 1 , wherein the first region is an anchor coding block, the second region is a current coding block, and the QP offset associated with the second region is identified based on a spherical sampling density of the second region.
3 . The method of claim 1 , wherein the first region is a slice that comprises a current coding block or a picture that comprises the current coding block, the second region is the current coding block, and the QP offset associated with the second region is identified based on a spherical sampling density of the second region.
4 . The method of claim 1 , wherein the QP offset associated with the second region is identified based on a coordinate of the second region.
5 . The method of claim 1 , wherein the QP offset for the second region is identified based on a QP offset indication in a bitstream.
6 . The method of claim 1 , wherein the second luma QP and the second chroma QP are determined at a coding unit level or a coding tree unit level.
7 . The method of claim 1 , wherein the determining of the second chroma QP comprises:
determining a weighted QP offset by applying a weighting factor to the QP offset; and
determining the second chroma QP by applying the weighted QP offset to the first chroma QP.
8 . The method of claim 7 , further comprising:
receiving a chroma QP weighting factor indication in a bitstream; and
determining the weighting factor for the QP offset based on the received chroma QP weighting factor indication.
9 . A device for decoding 360-degree video, comprising:
a processor configured to:
identify a first luma quantization parameter (QP) associated with a first region;
determine, based on the first luma QP, a first chroma QP associated with the first region;
identify a QP offset associated with a second region;
determine a second luma QP of the second region based on the first luma QP and the QP offset associated with the second region;
determine a second chroma QP of the second region based on the first chroma QP and the QP offset associated with the second region; and
perform an inverse quantization for the second region based on the second luma QP of the second region and the second chroma QP of the second region.
10 . The device of claim 9 , wherein the first region is an anchor coding block, the second region is a current coding block, and the processor is configured to identify the QP offset associated with the second region based on a spherical sampling density of the second region.
11 . The device of claim 9 , wherein the first region is a slice associated with a current coding block or a picture associated the current coding block, and the QP offset associated with the second region is identified based on a spherical sampling density of the second region.
12 . The device of claim 9 , wherein the second luma QP and the second chroma QP are determined at a coding unit level or a coding tree unit level.
13 . The device of claim 9 , wherein the QP offset associated with the second region is identified based on at least one of: a reception of the QP offset indication associated with the second region via a bitstream, or a coordinate of the second region.
14 . The device of claim 9 , wherein the processor is configured to determine the second chroma QP of the second region based on the QP offset being multiplied by a weighting factor.
15 . The device of claim 9 , wherein the determination of the second chroma QP comprises:
determining a weighted QP offset by applying a weighting factor to the QP offset; and
determining the second chroma QP by applying the weighted QP offset to the first chroma QP.