Witness the development of H.265

Adaptive Interpolation Filter for Video Coding

2010-07-21 KTA 2 Comments Views(15,666)

Why use interpolation in video coding?  
Motion-compensated prediction (MCP) is the key to the success of the modern video coding standards, as it removes the temporal redundancy in video signals and reduces the size of bitstreams significantly. With MCP, the pixels to be coded are predicted from the temporally neighboring ones, and only the prediction errors and the motion vectors (MV) are transmitted. However, due to the finite sampling rate, the actual position of the prediction in the neighboring frames may be out of the sampling grid, where the intensity is unknown, so the intensities of the positions in between the integer pixels, called sub-positions, must be interpolated and the resolution of MV is increased accordingly.  
Interpolation in H.264/AVC  
In H.264/AVC, for the resolution of MV is quarter-pixel, the reference frame is interpolated to be 16 times the size for MCP, 4 times both sides. As shown in Fig. 1(a), the interpolation defined in H.264 includes two stages, inter[......]

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Introduction to Test Model under Consideration (TMuC)

2010-06-27 H.265/HEVC 11 Comments Views(15,260)

TMuC is the initial test model of JCT-VC, but it is not formally adopted as a test model of the draft standard, as no thorough testing has been performed for such a possible combination of tools. The coding tools in TMuC will be further tested to confirm their effectiveness, before adopted in a formal test model.
TMuC provides more flexibility than H.264/AVC. The  basic coding unit, called coding tree block (CTB), which has a similar role to the macroblocks in H.264/AVC, can have variable sizes (a power of 2). The sizes of the largest and smallest CTBs are specified in the sequence parameter set (SPS). A frame is divided into non-overlapped largest CTBs (LCTB), e.g., 128×128, and then each LCTB can be further divided in a recursive tree representation.
Each CTB has its own prediction type (intra/inter) and prediction partition. The partition can be symmetric, just as in H.264/AVC, or asymmetric, e.g., 64×64 block can be partitioned into 64×16/64×48 or 16×64/48&[......]

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The First JCT-VC Meeting, Dresden, DE

2010-06-19 H.265/HEVC Post Comment Views(9,316)

During Apr. 15-23, 2010, the first meeting of JCT-VC was held in Dresden, DE. In the meeting, 27 responses to the Call for Proposal, issued in Jan. 2010, were reviewed and the associated video material was evaluated in extensive subjective tests.
Tentative Conclusions from CfP Responses Reviews
Coding tools used in respective proposals are listed in JCTVC-A203. High-level noteworthy aspects from the review of the proposals and the outcome of the subjective tests are outlined:

  • Substantial progress in coding efficiency has clearly been demonstrated, compared with H.264/AVC
  • There is no indication of a need to change the fundamental architecture of “conventional” hybrid video coding designs to achieve a substantial improvement
  • Inclusion of support of larger block sizes in a highly variable (typically tree-structured) block segmentation approach is a major common theme, although large block sizes were not found in all proposals that did well subjectively (and objectively)
  • Modif[......]

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Final Call for Proposals on H.NGVC/HVC Issued Jointly by VCEG and MPEG

2010-01-20 H.265/HEVC 3 Comments Views(5,970)

[Update]: A new email reflector,  jct-vc@lists.rwth-aachen.de, is created for discussions of the new team effort. For subscription, you should follow this link: http://mailman.rwth-aachen.de/mailman/listinfo/jct-vc. Only subscribers to the list will be able to send messages to this list.
During the 39th VCEG and 91st MPEG meeting held in Kyoto, Japan on January 17-22, 2010, the call for proposals (CfP) on video compression technology (H.NGVC/HVC) will be finally issued jointly by ITU-T SG16 Q.6 (VCEG) and ISO/IEC JTC1/SC29/WG11 (MPEG) on January 22, 2010. A Joint Collaborative Team (JCT) on Video Coding Standard Development will also be established accordingly between VCEG and MPEG.
Some minor modifications to draft CfP issued in November 2009 are made. The modifications involve the timeline, test conditions and test fees, etc., as follows:

  • Timeline

The timeline of the Call for Proposals is changed:
2010/01/22:                 Final Call for Proposals.
2010/01/22:                 For[......]

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Delay the Submission of Responses to CfP on HVC, or not?

2009-10-26 H.265/HEVC 4 Comments Views(3,852)

In the beginning plenary of 90th MPEG meeting on Oct. 26, several national bodies, such as USNB, FRNB, SGNB, and CNNB, recommended to delay the submission date of responses to the Call for Proposal (CfP) on HVC from December 2009 to March 2010. The major concerns from the national bodies are:

  • the need of sufficient time to finalize the establishment of collaborative team with VCEG and only then issue a joint CfP;
  • the need of sufficient time to determine the cost of the subjective evaluation tests after the CfP is finalized;
  • the need of sufficient time to refine the CfP test conditions/materials and only then generate the proposed bitstreams;
  • the need of sufficient time to define the complexity evaluation criterion in an objective method for quantitative analysis,
  • the need of sufficient time to perform the subjective evaluation tests but currently planned in the year-end holidays period.

This recommendation aroused controversy between the delegates of national bodies and the convenor,[......]

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

2009-09-22 KTA 15 Comments Views(13,620)

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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Adaptive Post/Loop Filters in JM/KTA – Part 2

2009-08-23 KTA 12 Comments Views(17,109)

3. Adaptive Loop Filter
As far as adaptive loop filter (ALF) is concerned, there are three types of ALF: frame-based, block-based and quadtree-based ALFs. All of them are based on wiener filter, but with different filtering control basis. In frame-based ALF [VCEG-C437/AI14, C402], only one picture level flag is used to signal the decision of filtering or non-filtering.
Although wiener filter can restore the reconstructed picture to the original picture globally, there are degraded pixels locally. Since the degraded area reduce the filtering efficiency, if these areas are not filtered, the capabilities of picture restoration and loop filtering are improved. Therefore, block-based ALF [VCEG-AI18/AJ13] use explicit flags for filtering on-off on block by block basis, while quadtree-based ALF [VCEG-C181/AK22] introduces a quadtree data structure to carry out the variable-size block filtering.
3.1 Block-based Adaptive Loop Filter
Block-based ALF is an improvement of frame-based ALF. Figure 2[......]

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Adaptive Post/Loop Filters in JM/KTA – Part 1

2009-08-22 KTA Post Comment Views(7,495)

1. Introduction
The basic idea of adaptive post/loop filter is the same. Both of them use adaptive wiener filtering technique to improve the quality of reconstructed picture which is degraded by compression. The difference between them is whether the filtering process is applied in or out of the core coding loop, as shown in Figure 1,  to improve the quality of reconstructed picture or just displayed picture.
kta_diagram
Figure 1. Block diagram of JM/KTA
2. Adaptive Post Filter
In H.264/AVC, there is already an existing post-filter hint SEI message [JVT-S030/T039/U035] which provides the coefficients of a post-filter or correlation information for the design of a post-filter for potential use in post-processing of the output decoded pictures to obtain improved displayed quality.
To find the coefficients of adaptive wiener filter, the following cost function based on the whole frame is minimized:
Eq1 (1)
where R is the reconstructed picture, R’ is the filtered picture, and I is the original pic[......]

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