KTA employs two concatenating loop filters: the deblocking loop filter and the adaptive loop filter. The deblocking loop filter, inherited from H.264/AVC, alleviates the blocking artifacts caused by the block-based DCT+MCP video coding framework. It uses a bank of low-pass filters, which are adaptively applied to block boundaries according to the boundary strength (BS), and provides better visual quality [...]

Permanent Link: Two Loop Filters in KTA

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 [...]

Permanent Link: Adaptive Interpolation Filter for Video Coding

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 [...]

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

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 [...]

Permanent Link: Adaptive Post/Loop Filters in JM/KTA – Part 2

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 [...]

Permanent Link: Adaptive Post/Loop Filters in JM/KTA – Part 1

4. Rate-Distortion Optimized Quantization Previously, adaptive rounding was proposed to improve quantization, which captures the statistics of the incoming residual signal and adjusts the rounding offsets accordingly. However, the adaptive rounding quantization is still based on the criterion which minimizes the mean-squared quantization error between the original signal and the quantization reconstructed signal. From the [...]

Permanent Link: Quantization Techniques in JM/KTA – Part 4

3. Adaptive Rounding Encoding Technique using an Equal Expected-Value Rule As discussed above, if the input p.d.f. is Laplacian distributed and if we can estimate λ, then the optimal f can be found analytically. But, usually the estimate of input p.d.f. is not available, then, how to select the rounding offset f? In order to [...]

Permanent Link: Quantization Techniques in JM/KTA – Part 3

2. Principle of H.264/AVC Normal Quantization Scheme 2.1. Scalar dead-zone quantization In this section the principle of H.264/AVC normal quantization scheme is described in a generalized form. A scalar quantizer for input signal W can be decomposed into a function Z=C[W] called a classification rule that selects an integer-valued class identifier called the quantization index [...]

Permanent Link: Quantization Techniques in JM/KTA – Part 2