Abstract: In one example, an apparatus for encoding video data includes a video encoder configured to scan a two-dimensional block of transform coefficients to produce a one-dimensional vector of the transform coefficients, determine values indicative of whether the transform coefficients in the one-dimensional vector are significant; and entropy encode at least one of the values using a context model selected based on at least a percentage of significant coefficients in a predetermined number of the values encoded before the at least one of the values.

Abstract: Video coding devices and methods use a function-based definition of scan order to scan transform coefficients associated with a block of residual video data. A video coder may define a scan order for coefficients based on a predefined function and one or more parameter values. A video encoder may use a function-based scan order to scan a two-dimensional array of coefficients to produce a one-dimensional array of coefficients for use in producing encoded video data. The video encoder may signal the parameters to a video decoder, or the video decoder may infer one or more of the parameters. The video decoder may use the function-based scan order to scan a one-dimensional array of coefficients to reproduce the two-dimensional array of coefficients for use in producing decoded video data. In each case, the scan order may vary according to the parameter values, which may include block size, orientation, and/or orientation strength.

Abstract: During the prediction stage of a video encoding and/or decoding process, a video coder can use relatively longer filters for certain motion vectors pointing to certain sub-pixel positions and relatively shorter filters for motion vectors pointing to other sub-pixel positions, where a longer filter generally refers to an interpolation filter with a greater number of filter coefficients, also called taps, while a shorter filter generally refers to an interpolation filter with fewer taps.

Abstract: 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.

Abstract: In one example, an apparatus for encoding video data includes a video encoder configured to calculate a residual block for a block of video data based on a predicted block formed using an intra-prediction mode, and transform the residual block using a transform mapped from the intra-prediction mode. In another example, an apparatus includes video encoder configured to receive an indication of a first intra-prediction mode in a first set of intra-prediction modes for a block of video data, determine a second intra-prediction mode from a second set of intra-prediction modes, smaller than the first set of intra-prediction modes, to which the first intra-prediction mode is mapped, determine a directional transform to which the second intra-prediction mode is mapped, and apply the directional transform to residual data of the block.

Abstract: In one example, an encoder may apply a plurality of pre-defined interpolation filters to units of video data, such as frames of reference video, in order to generate a plurality of different interpolated prediction data. The encoder may also at times determine that a new interpolation filter or set of interpolation filters might improve coding quality by either improving video compression or improving reconstructed image quality. The encoder may also signal to a video decoder whether one of the pre-defined interpolation filters was used or a new set of interpolation filters was used. The encoder may also signal to a video decoder whether to continue using the new set of interpolation filters, or whether to revert back to using the pre-defined set of interpolation filters. A video decoder can decode video data based on data received from the video encoder.

Abstract: In general, techniques are described for implementing an 8-point inverse discrete cosine transform (IDCT). An apparatus comprising an 8-point inverse discrete cosine transform (IDCT) hardware unit may implement these techniques to transform media data from a frequency domain to a spatial domain. The 8-point IDCT hardware unit includes an even portion comprising factors A, B that are related to a first scaled factor (?) in accordance with a first relationship. The 8-point IDCT hardware unit also includes an odd portion comprising third, fourth, fifth and sixth internal factors (G, D, E, Z) that are related to a second scaled factor (?) in accordance with a second relationship. The first relationship relates the first scaled factor to the first and second internal factors. The second relationship relates the second scaled factor to the third, fourth, fifth and sixth internal factors.

Abstract: In general, techniques are described for implementing a 16-point inverse discrete cosine transform (IDCT) that is capable of applying multiple IDCTs of different sizes. For example, an apparatus comprising a 16-point inverse discrete cosine transform of type II (IDCT-II) unit may implement the techniques of this disclosure. The 16-point IDCT-II unit performs these IDCTs-II of different sizes to transform data from a spatial to a frequency domain. The 16-point IDCT-II unit includes an 8-point IDCT-II unit that performs one of the IDCTs-II of size 8 and a first 4-point IDCT-II unit that performs one of the IDCTs-II of size 4. The 8-point IDCT-II unit includes the first 4-point DCT-II unit. The 16-point IDCT-II unit also comprises an inverse 8-point DCT-IV unit that includes a second 4-point IDCT-II unit and a third 4-point IDCT-II unit. Each of the second and third 4-point IDCT-II units performs one of the IDCTs-II of size 4.

Abstract: In general, techniques are described for implementing a 16-point discrete cosine transform (DCT) that is capable of applying multiple IDCT of different sizes. For example, an apparatus comprising a 16-point discrete cosine transform of type II (DCT-II) unit may implement the techniques of this disclosure. The 16-point DCT-II unit performs these DCTs-II of different sizes to transform data from a spatial to a frequency domain. The 16-point DCT-II unit includes an 8-point DCT-II unit that performs one of the DCTs-II of size 8 and a first 4-point DCT-II unit that performs one of the DCTs-II of size 4. The 8-point DCT-II unit includes the first 4-point DCT-II unit. The 16-point DCT-II unit also comprises an 8-point DCT-IV unit that includes a second 4-point DCT-II unit and a third 4-point DCT-II unit. Each of the second and third 4-point DCT-II units performs one of the DCTs-II of size 4.

Abstract: This disclosure describes techniques for performing entropy encoding and decoding of video coefficients using a joint context model shared between transform units having different sizes. For example, the joint context model may be shared between transform units having a first size of 32×32 and transform units having a second size of 16×16. Performing entropy coding using a joint context model shared between transform units having different sizes may reduce an amount of memory necessary to store contexts and probabilities, and reduce computational costs of maintaining context models. In one example, the joint context model may be shared between transform units having the first size with coefficients zeroed out to generate a retained coefficient block having the second size and transform units having the second size. In another example, the joint context model may be shared between transform units having the first size and transform units having the second size.

Abstract: This disclosure describes techniques for performing entropy encoding and decoding of video coefficients using a joint context model shared between transform units having different sizes. For example, the joint context model may be shared between transform units having a first size of 32×32 and transform units having a second size of 16×16. Performing entropy coding using a joint context model shared between transform units having different sizes may reduce an amount of memory necessary to store contexts and probabilities, and reduce computational costs of maintaining context models. In one example, the joint context model may be shared between transform units having the first size with coefficients zeroed out to generate a retained coefficient block having the second size and transform units having the second size. In another example, the joint context model may be shared between transform units having the first size and transform units having the second size.

Abstract: In one example, an apparatus includes a video encoder configured to partition a block of video data into a first partition and a second partition using a geometric motion partition line, calculate a slope value and a y-intercept value of the geometric motion partition line, wherein the slope value and the y-intercept value comprise integer values, calculate a mask indicative of pixels of the block in the first partition and pixels of the block in the second partition, encode the first partition and the second partition based on the mask, and output the encoded first partition, the encoded second partition, the slope value, and the y-intercept value. This may allow for a fixed point implementation. A video decoder may receive the slope and y-intercept values to calculate the mask and decode the block based on the mask.

Abstract: This disclosure describes video encoding and decoding techniques in which a first order prediction process and a second order prediction process are used in combination to generate predictive video blocks for video coding. First order prediction may be similar to conventional motion estimation and motion compensation that generates residual video blocks. The second order prediction may involve a process similar to conventional intra-prediction, but is performed on the residual video blocks. The techniques of this disclosure may pre-define the second order prediction to a specific mode, such as a mode similar to the intra-DC mode used in intra coding. In addition, the techniques of this disclosure may combine aspects of the first order and second order prediction into a single process so that the effects of second order prediction on the residuals are taken into account during the first order prediction process, which may improve compression.

Abstract: In general, techniques are described for implementing an 8-point discrete cosine transform (DCT). An apparatus comprising an 8-point discrete cosine transform (DCT) hardware unit may implement these techniques to transform media data from a spatial domain to a frequency domain. The 8-point DCT hardware unit includes an even portion comprising factors A, B that are related to a first scaled factor (?) in accordance with a first relationship. The 8-point DCT hardware unit also includes an odd portion comprising third, fourth, fifth and sixth internal factors (G, D, E, Z) that are related to a second scaled factor (?) in accordance with a second relationship. The first relationship relates the first scaled factor to the first and second internal factors. The second relationship relates the second scaled factor to the third internal factor and a fourth internal factor, as well as, the fifth internal factor and a sixth internal factor.

Abstract: In one example, this disclosure describes a method of decoding video data. The method comprises receiving a coding unit (CU) of encoded video data. The CU is partitioned into a set of block-sized coded units (CUs) according to a quadtree partitioning scheme, and decoding one or more syntax elements for the CU to indicate a change in a quantization parameter for the CU relative to a predicted quantization parameter for the CU only if the CU includes any non-zero transform coefficients. The one or more syntax elements are decoded from a position within the encoded video data after an indication that the CU will include at least some non-zero transform coefficients, and before the transform coefficients for the CU.

Abstract: Video coding devices and methods use a function-based definition of scan order to scan transform coefficients associated with a block of residual video data. A video coder may define a scan order for coefficients based on a predefined function and one or more parameter values. A video encoder may use a function-based scan order to scan a two-dimensional array of coefficients to produce a one-dimensional array of coefficients for use in producing encoded video data. The video encoder may signal the parameters to a video decoder, or the video decoder may infer one or more of the parameters. The video decoder may use the function-based scan order to scan a one-dimensional array of coefficients to reproduce the two-dimensional array of coefficients for use in producing decoded video data. In each case, the scan order may vary according to the parameter values, which may include block size, orientation, and/or orientation strength.

Abstract: This disclosure describes techniques for performing entropy encoding and decoding of video coefficients using a joint context model shared between transform units having different sizes. For example, the joint context model may be shared between transform units having a first size of 32×32 and transform units having a second size of 16×16. Performing entropy coding using a joint context model shared between transform units having different sizes may reduce an amount of memory necessary to store contexts and probabilities, and reduce computational costs of maintaining context models. In one example, the joint context model may be shared between transform units having the first size with coefficients zeroed out to generate a retained coefficient block having the second size and transform units having the second size. In another example, the joint context model may be shared between transform units having the first size and transform units having the second size.

Abstract: This disclosure describes techniques for performing entropy encoding and decoding of video coefficients using a joint context model shared between transform units having different sizes. For example, the joint context model may be shared between transform units having a first size of 32×32 and transform units having a second size of 16×16. Performing entropy coding using a joint context model shared between transform units having different sizes may reduce an amount of memory necessary to store contexts and probabilities, and reduce computational costs of maintaining context models. In one example, the joint context model may be shared between transform units having the first size with coefficients zeroed out to generate a retained coefficient block having the second size and transform units having the second size. In another example, the joint context model may be shared between transform units having the first size and transform units having the second size.

Abstract: 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.

Abstract: This disclosure describes techniques for entropy coding bins representing video data symbols with reduced bottlenecks in the entropy coding process. The techniques of this disclosure enable an entropy coding device to perform entropy coding of bins grouped into bin subsets from across different bin groups, e.g., context groups or probability groups, using variable length codewords. In one example, the bins may be assigned to context groups with no context dependencies between the context groups. In another example, the bins may be assigned to probability groups associated with different intervals of probability states. The bins may be grouped into the bin subsets according to determined formations of the bin subsets. In this way, the entropy coding device may reduce an amount of bin and codeword buffering by efficiently forming the bin subsets and designing variable length codewords for each of the bin subsets.