The intra prediction in H.264/AVC is a type of spatial domain directional prediction, which means different intra prediction modes represent different prediction directions, such as horizontal, vertical, and diagonal. An intra-coded MB can be partitioned into 4×4, 8×8, or 16×16 intra prediction blocks. The 4×4 and 8×8 intra prediction blocks have nine prediction directions, respectively, and the 16×16 block has four. Hence, totally 22 (9+9+4) intra prediction modes are used in H.264/AVC. The residue usually has high energy along the direction of prediction, as edges are more difficult to be predicted than smooth areas.
Mode-dependent directional transform (MDDT) was proposed to compact the residue produced by intra prediction. It consists of a series of pre-defined separable transforms; each transform is efficient in compacting energy along one of the prediction directions, thus favoring one of the intra modes. The type of MDDT is coupled with the selected[......]

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Permanent Link: Mode-Dependent Directional Transform (MDDT) in JM/KTA

The technique of 1/8-pel interpolation [AD09] was proposed for motion-compensated prediction (MCP) and adopted in KTA software. Three types of interpolation filters are used for 1/2-, 1/4-, and 1/8-pel sub positions, respectively.

• [-3, 12, -39, 158, 158, -39, 12, -3]/256 for 1/2-pel sub positions.
• [-3, 12, -37, 229, 71, -21, 6, -1]/256 and [-1, 6, -21, 71, 229, -37, 12, -3]/256 for 1/4-pel sub positions.
• Bilinear filter for 1/8-pel sub positions.

  The frequency response of the interpolation filter is shown in the following figure. As can be seen, it is almost an ideal low-pass filter with a gain of 8 and a cutoff frequency π/8.

  According to the performance reported in the proposal, the gain on CIF/QCIF sequences is quite significant, i.e., up to 14% bit-rate reduction. I tested this technique based on a set of HD sequences. As shown in Table 1, the R-D performance is measured by BDPSNR [1], i.e., PSNR improvement at the same bit-rate or bit-rate reduction at the same PSNR.
 

 
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Permanent Link: R-D performance of 1/8-pel MCP on HD sequences

In the Geneva meeting held in Feb. 2009, a proposal with the title “Video Coding Using Extended Block Sizes” was adopted by KTA, where the MB size is extended up to 64×64 and the motion partitions are scaled accordingly. At the same time, a 2D order-16 transform was also proposed for transforming the residual blocks with the size larger than or equal to 16×16. The transformation matrix of the proposed 2D order-16 transform is given as below, which is obtained by scaling the transformation matrix of 2D order-16 DCT by the factor 128 and rounding, and is non-orthogonal.

  Non-orthogonality will inevitably introduce transform error. Before analyzing the transform error quantitatively, let’s recall two properties of orthogonal transforms. Firstly, signals can be reconstructed perfectly if no quantization is performed in the transform domain. Secondly, if quantization is performed in the transform domain, the average variance (or energy) of the reconstruction er[......]

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Permanent Link: Transform error introduced by non-orthogonality

The latest KTA software is JM11KTA2.3, which integrates the coding tools adopted in the Geneva meeting (Jan. 2009) and before.  

1. Inter prediction
   1. Adaptive interpolation filter (AIF)
      • 2-D non-separable AIF (AD08, AE16)
      • Separable AIF (COM16-C219, AG10)
      • Directional AIF (DAIF) (AG21, AG22, AH17, AH18)
      • Enhanced DAIF (E-DAIF) (AI12,  COM16-C125, COM16-C126)
      • Enhanced AIF (EAIF) (COM16-C464, AI38, AJ30)
      • Switch interpolation filters with offsets (SIFO) (COM16-C463, AI35, AJ29, COM16-C126)
      • High precision filter (HPF) (AI33)
      • Single-Pass Encoding (AJ29, AK26)
   2. 1/8-pel MCP (AD09)
   3. Extended MCP block size (COM16-C123)
   4. Competition-based MV prediction (AC06r1)
2. Transform and quantization
   1. Mode-dependent directional transform (MDDT) (AF15, AG11, AH20, AJ24, AI36)
   2. Very large block transform (COM16-C123)
   3. Adaptive prediction error coding (APEC) (AB06, AD07, AE15)
   4. Adaptive quantization matrix selection (AQMS) (AC07, AD06, AF08, AI19)
   5. Rate-distortion optimized quantization (RDO-Q) (AH21)
3. Entropy coding[......]

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Permanent Link: KTA software JM11KTA2.3

H.265 is a long-term video coding standard, launched by VCEG. As indicated in ITU-T SG16’s homepage, VCEG plans to complete the requirement definition and begin the detailed algorithm design for H.265 in the study period 2005-2008, and if the progress in contribution technology is sufficient, H.265 is expected to be finalized in 2009-2010.
Currently, H.265 hasn’t been formalized and VCEG keeps seeking proposals and information regarding the possibility of a major gain in performance to justify the step from H.264 to H.265. Though the necessary scope of H.265 is yet to be determined, it is agreed that among the goals will be [AA01]:

• simplicity and “back to basics” approach
• high coding efficiency, e.g., two times compared with H.264
• computational efficiency, considering both encoder and decoder
• loss/error robustness
• network friendliness
• other considerations as necessary 

Backward/forward compatibility is not assumed to be required for H.265, as H.265 is a brand [......]

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Permanent Link: Current status of H.265 (as at July 2008)

Hello, everybody, welcome to H265.net!
This blog is dedicated to the development of H.265 that is still in its infancy. Not only does this blog records the events of H.265, but it also discusses the (potential) techniques for H.265, i.e., the proposals in VCEG. Please feel free to post your comments and suggestions, no matter you are a beginner or an expert.
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Should you have suggestions for the construction of this blog, please send an e-mail to admin@h265.net. Thank you very m[......]

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Permanent Link: Welcome to H265.net