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DEBLOCKING FILTER

Present: Pham Ngoc Giao

Professor: Kim - Jong Nam

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Contents

Position of deblocking filter in H.264?1

Why H.264 use deblocking filter?2

Function and operation of deblocking filter 3

4 Reference

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Position of deblocking filter

Transform &Quantization

Motion

Estimation

MotionCompensation

PictureBuffering

EntropyCoding

IntraPrediction

Intra/Inter ModeDecision

Inverse Quantization& Inverse Transform

DeblockingFilter

+

-

++

Video Input

Bitstream

Output

Encoder H.264

Using Inter mode

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Position of deblocking filterDecoder H.264

MotionCompensation

EntropyDecoding

IntraPrediction

Intra/Inter ModeSelection

Inverse Quantization& Inverse Transform

DeblockingFilter

+

+BitstreamInput Video

Output

PictureBuffering

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Why H.264 use deblocking filter

After inverse quantization and inverse transform, macroblocks have blocking

distortion and blocking artifacts. Thus, frame image is used for motion estimation

and motion compensation in inter mode, has noise and errors => using blocking

filter to reduce noise, smooth blocks and improve frame.

MotionCompensation

EntropyDecoding

IntraPrediction

Intra/Inter ModeSelection

Inverse Quantization& Inverse Transform

DeblockingFilter +

+BitstreamInput Video

Output

PictureBuffering

Noise, distortion and artifacts

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Function of deblocking filter

Reduceblocking

distortion

Improvequality of decodedpicture

Reduceblockingartifacts

Smoothblockedges

functions

Deblocking filter:

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Operation of deblocking filter

Filtering is applied to horizontal or verticaledges of 4 x 4 blocks in a macroblock,adaptively on the several levels: slice, block-edge, sample

Vertical edges(chroma)

Vertical edges(luma)

Horizontal edges(luma)

Horizontal edges(chroma)

16*16 Macroblock 16*16 Macroblock

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Operation of deblocking filter

Each filtering operation affects up to three samples oneither side of the boundary. The strength of the filter (theamount of filtering) depends on the current quantiser, thecoding modes of neighbouring blocks and the gradient ofimage samples across the boundary

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Operation of deblocking filter

Determine Boundary strengths: H264/MPEG4 has a set offour boundary strengths

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Operation of deblocking filter

Decision Filter:

+ A group of samples from the set (p2, p1, p0, q0, q1,

q2) is filtered only if:(a) BS > 0 and

(b) |p0 q 0|

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Operation of deblocking filter

Determine valid edge:

In a given MB an edge is selected for de-blocking

if : the slice to which the current MB belongs is

enabled for de-blocking the corresponding neighboring block is

available

For the horizontal edge of a field mode block in a

frame, both the lines 0 and 1 of the block are selected

for de-blocking if the top-right macro-block pair is a

field MB

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Operation of deblocking filter

Da

Data flow for de-blocking process

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Operation of deblocking filter

Da

Algorithm for data flow

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Operation of deblocking filter

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Operation of deblocking filter

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Operation of deblocking filter

[1] ITU-T Recommendation, H.264 Advanced VideoCoding for Generic Audiovisual Services, 03/2005

[2] ITU-T Recommendation, H.264.1 ConformanceSpecification for H.264 Advanced Video Coding, 03/2005

[3] Iain E. G. Rechardson, H.264 and MPEG-4 VideoCompression, John Wiley and Sons, 2003

[4] Wu Di, Gao Wen, Hu Mingzeng, Ji Zhenzhou, An Exp-Golomb Encoder and Decoder Architecture forJVT/AVS, IEEE, 2003

[5] Overview of the H.264/AVC Video Coding StandardThomas Wiegand, Gary J. Sullivan, Senior Member, IEEE,

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