摘要:
This disclosure describes techniques for intra-prediction mode signaling for video coding. In one example, a video coder is configured to determine, for a block of video data, a set of most probable intra-prediction modes such that the set of most probable intra-prediction modes has a size that is equal to a predetermined number that is greater than or equal to two. The video coder is also configured to code a value representative of an actual intra-prediction mode for the block based at least in part on the set of most probable intra-prediction modes and code the block using the actual intra-prediction mode. The video coder may further be configured to code the block using the actual intra-prediction mode, e.g., to encode or decode the block. Video encoders and video decoders may implement these techniques.
摘要:
This disclosure describes techniques for mitigating rounding errors in a fixed-point transform associated with video coding by applying a variable localized bit-depth increase at the transform. More specifically, the techniques include selecting a constant value based on a size of a fixed-point transform in a video coding device and applying a variable localized bit-depth increase at the transform with a value equal to the constant value. Applying the variable localized bit-depth increase includes left-shifting a transform input signal by a number of bits equal to the constant value before the fixed-point transform, and right-shifting a transform output signal by a number of bits equal to the constant value after the fixed-point transform. The constant value is selected from a plurality of constant values stored on the video coding device. Each of the constant values is pre-calculated for one of a plurality of different transform sizes supported by the video coding.
摘要:
The example techniques described in this disclosure provide for an efficient manner to encode or decode a video block of a picture using a single reference picture list. The single reference picture list may include identifiers for reference picture or pictures used to encode or decode the video block. In some examples, a video encoder or decoder may encode or decode a video block that is predicted from two reference pictures using the single reference picture list, and encode or decode a video block that is predicted from one reference picture using the same, single reference picture list.
摘要:
This disclosure relates to techniques for constructing a combined reference picture list, List C, based on List 0 and List 1, used for uni-directional prediction of video blocks in any direction. The techniques include coding one or more syntax elements defined to indicate construction information for List C, and performing reference picture list construction for List C from List 0 and List 1 based on the syntax elements. The one or more syntax elements may indicate that List C is used for uni-directional prediction, and may also indicate a number of reference pictures identified in List C and a reference index of a reference picture for each entry in List C. Each coded video block of a B slice may have an associated syntax element, i.e., inter_pred_idc, to indicate whether the video block is bi-predicted from List 0 and List 1 (Bi) or uni-directional predicted from List C (Pred_LC).
摘要:
A method of coding video data includes determining a candidate motion vector for each of one or more candidate portions of a video frame and determining a current motion vector for a current portion of a current frame. The current motion vector identifies a portion of a reference frame that at least partially matches the current portion of the current frame. The method also includes calculating a motion vector difference between the current motion vector and each of the candidate motion vectors, selecting one of the candidate motion vectors based on the calculated motion vector differences, signaling an index identifying the candidate portion having the selected one of the candidate motion vectors, and signaling the corresponding motion vector difference calculated with respect to the selected one of the candidate motion vectors.
摘要:
In one example, this disclosure describes a method of codeword adaptation for variable length coding. The method includes applying a first codeword adaptation scheme to groups of codewords in a variable length coding (VLC) table to change mappings of codewords within the groups to events in the VLC table; and applying a second codeword adaptation scheme to individual codewords within the groups of codewords in the VLC table to change mappings of the codewords to the events within the groups in the VLC table.
摘要:
In one example, a video decoder is configured to determine whether a component of a transform unit of a coding unit of video data includes at least one non-zero coefficient based on a codeword for the transform unit, determine whether the transform unit is split into sub-transform units based on the codeword, and decode the transform unit based on the determinations. In another example, a video encoder is configured to determine whether a component of a transform unit of a coding unit of video data includes at least one non-zero coefficient, determine whether the transform unit is split into sub-transform units, select a codeword from a variable length code table, wherein the variable length code table provides an indication that the codeword corresponds to the determinations, and provide the codeword for the transform unit.
摘要:
A video encoder can maintain, by generating, storing, adjusting, altering, and/or updating, one or more variable length coding (VLC) tables that represent a mapping of prediction modes to codewords. One or more codewords representing a selected prediction mode can be communicated to the decoder for a CU of a frame. The decoder maintains one or more VLC tables that match the VLC tables maintained by the video encoder. Thus, based on the one or more codewords received from the video encoder, the video decoder can determine the prediction mode used to encode a CU.
摘要:
This disclosure relates to techniques for reducing a cost of coding prediction information in video coding. Video blocks in a generalized P/B (GPB) frame are encoded using up to two motion vectors calculated from reference pictures in two separate reference picture lists that are identical. When one of the reference picture lists is preferred over the other reference picture list, the preferred reference picture list may be used for unidirectional prediction, by default. When a GPB frame is enabled such that the first and second reference picture lists are identical, either of the first and second reference picture lists may be used for unidirectional prediction. The techniques include coding one or more syntax elements indicating that a video block is coded using one of the unidirectional prediction mode with respect to a reference picture in a reference picture list and the bidirectional prediction mode using less than two bits.
摘要:
In one example, a device for coding video data includes a video coder configured to configured to code information representative of whether an absolute value of an x-component of a motion vector difference value for a current block of video data is greater than zero, code information representative of whether an absolute value of a y-component of the motion vector difference value is greater than zero, when the absolute value of the x-component is greater than zero, code information representative of the absolute value of the x-component, when the absolute value of the y-component is greater than zero, code information representative of the absolute value of the y-component, when the absolute value of the x-component is greater than zero, code a sign of the x-component, and when the absolute value of the y-component is greater than zero, code a sign of the y-component.