1. Block Distortion
(Blocking, Blockiness)
• 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-1
NL 10/26/2013
* also called Gibbs effect

2. Staircase Noise
• Special case of blocking noise along diagonal or curved
edges; here, blocking distortion looks like staircase
Working-2
NL 10/26/2013
* also called Gibbs effect

3. 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-3
NL 10/26/2013
* also called Gibbs effect

4. 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-4
NL 10/26/2013
* also called Gibbs effect

5. Mosquito Noise (Gibbs Effect)
• Haziness, shimmering, blotchy noise around objects/edges
– Varies from frame to frame, like mosquitos flying around
person’s head
Working-5
NL 10/26/2013

6. 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-6
NL 10/26/2013
* also called Gibbs effect

7. 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-7
NL 10/26/2013
* also called Gibbs effect

8. Jerkiness (Temporal Artifacts)
(Not the best
example; must be in
Slideshow to play)
• Motion (originally smooth and continuous) that is perceived
as series of distinct “snapshots”
– Caused by skipping video frames
Working-8
NL 10/26/2013