Video compression artifacts and how to identify them
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This document discusses and provides examples of common video compression artifacts, including blocking distortion caused by coarse quantization of neighboring blocks, staircase noise along diagonal edges, blurring from quantization of high frequencies, color bleeding across boundaries from chroma subsampling, mosquito noise around edges from frame to frame, ringing halos around objects from high frequency quantization, and random quantization noise.
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Video compression artifacts and how to identify them
- 1. Examples of Common Video Compression Artifacts Nigel Lee Video Quality Analysis Work 05 Aug 2013 Working-1 NL 11/1/2013
- 2. Block Distortion (Blocking, Blockiness, Pixelation) • Visibility of underlying block encoding structure – Caused by coarse quantization, with different quantization applied to neighboring blocks • More visible in smoother areas of picture Working-2 NL 11/1/2013
- 3. Staircase Noise • Special case of blocking noise along diagonal or curved edges; here, blocking distortion looks like staircase Working-3 NL 11/1/2013
- 4. Blurring (Fuzziness, “Unsharpness”) • Reduction in sharpness of edges, spatial details – Caused by quantization/truncation of high-frequency transform (DCT/DWT) coefficients during compression • More noticeable around edges, textured regions Working-4 NL 11/1/2013
- 5. Color Bleeding (Smearing) Original Compressed • Colors of contrasting hue/saturation bleed across sharp brightness boundaries, looks like “sloppy painting” – Caused by chroma subsampling • Worse in images with high color detail Working-5 NL 11/1/2013
- 6. Mosquito Noise (Gibbs Effect) • Haziness, shimmering, blotchy noise around objects/edges – Varies from frame to frame, like mosquitos flying around person’s head Working-6 NL 11/1/2013
- 7. Ringing (Echoing, Ghosting) • Halo surrounding objects and edges – Caused by quantization/truncation of high-frequency transform (DCT/DWT) coefficients during compression • Doesn’t move around frame-to-frame (unlike mosquito noise) Working-7 NL 11/1/2013
- 8. Quantization Noise • Looks like random noise process (snow); can be grey or colored, but not uniform over image – Caused by quantization of DCT coefficients Working-8 NL 11/1/2013