| CPC H04N 19/126 (2014.11) [H04N 19/124 (2014.11); H04N 19/172 (2014.11); H04N 19/176 (2014.11); H04N 19/186 (2014.11); H04N 19/187 (2014.11); H04N 19/196 (2014.11); H04N 19/197 (2014.11); H04N 19/34 (2014.11); H04N 19/46 (2014.11); H04N 19/463 (2014.11); H04N 19/593 (2014.11); H04N 19/61 (2014.11); H04N 19/70 (2014.11); H04N 19/184 (2014.11)] | 20 Claims |

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1. One or more non-transitory computer-readable media having stored thereon computer-executable instructions for causing one or more processing units, when programmed thereby, to perform operations of a computer-implemented video decoder, the operations comprising:
receiving encoded data for a picture organized in multiple channels, the multiple channels including two chroma channels, the encoded data including quantization parameter (“QP”) information that indicates multiple QPs that at least in part parameterize inverse quantization for the picture, the QP information including an index for a given chroma channel among the two chroma channels for a current unit of the picture; and
decoding the encoded data to reconstruct the picture, including varying inverse quantization spatially and between the multiple channels for the picture, wherein the decoding the encoded data to reconstruct the picture includes, for the current unit:
determining a unit-level QP of a spatially neighboring unit, including:
determining whether an actual QP of the spatially neighboring unit is available; and
depending on whether the actual QP of the spatially neighboring unit is available, assigning the actual QP of the spatially neighboring unit to be the unit-level QP of the spatially neighboring unit or substituting another QP as the unit-level QP of the spatially neighboring unit;
determining a predicted QP based at least in part on the unit-level QP of the spatially neighboring unit; and
determining a unit-level QP for the given chroma channel for the current unit based at least in part on the predicted QP and the index for the given chroma channel for the current unit.
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