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A Method to Suppress Visual Dithering in Consecutive Intra-Refresh Encoding

IP.com Disclosure Number: IPCOM000239471D
Publication Date: 2014-Nov-10
Document File: 5 page(s) / 150K

Publishing Venue

The IP.com Prior Art Database

Abstract

Obvious visual dithering may be observed when encoding still video with consecutive intra-refresh at predefined resolution/bitrate/refresh rate combinations. Dynamically disabling the deblocking filter on a frame basis, disabling the deblocking filter on a CIR region only, or isolating a CIR region in a slice helps to effectively suppress the dithering.

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A Method to Suppress Visual Dithering in Consecutive Intra-Refresh Encoding

Abstract

Obvious visual dithering may be observed when encoding still video with consecutive intra-refresh at predefined resolution/bitrate/refresh rate combinations. Dynamically disabling the deblocking filter on a frame basis, disabling the deblocking filter on a CIR region only, or isolating a CIR region in a slice helps to effectively suppress the dithering.

Acronyms
MB - macroblock
CIR - consecutive intra refresh
PSNR - peak signal to noise ratio

What’s the problem?

When encoding screen or other still videos to video streams in H.264 or like standards, and encoding with consecutive intra-refresh at required resolution/bitrate/refresh rate combinations (e.g., 720p@5Mbps, 10% refresh rate) to ensure channel error recovery, there will probably be visual dithering in the encoded stream obvious to see because the video should be stationary.

What’s the solution?

Use below methods in encoder to suppress the visual dithering.

1) Dynamically disable deblocking filter by 2-pass encoding.
Encode the current frame twice. The first encoding with deblocking filter disabled, the second encoding with deblocking filter enabled. If the first encoding output has obvious higher PSNR than the second encoding, choose the first encoding.

2) Disable deblocking filter for MBs in CIR region

CIR region is marked grey. Disable deblocking filter for MBs in this region, and keep deblocking filter enabled for MBs outside this region. A variation is to dynamically disable deblocking filter for CIR region using PSNR comparison similar to method 1).

3) Encode to multiple slices and fit CIR region to a slice
For example, encode each slice using same number of MBs as those in CIR region, so that CIR region exactly fits in a slice.

The picture is encoded to slices with same number of MBs. The CIR region ma...