Subjective Quality Assessment in Stereoscopic Video Based on Analyzing Parallax and Disparity
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The document discusses subjective quality assessment of stereoscopic video, focusing on visual discomfort caused by variations in 3D disparity. It outlines a methodology for characterizing video sequences, analyzing transitions, and evaluating viewer reactions through subjective assessments. The findings suggest that motion and the placement of negative parallax in 3D sequences significantly influence visual discomfort, leading to recommendations for content creators and tools for automatic discomfort detection.
Subjective Quality Assessment in Stereoscopic Video Based on Analyzing Parallax and Disparity
- 1. Subjective Quality Assessment in Stereoscopic Video Based on Analyzing Parallax and Disparity Juan Pedro López Velasco, Juan Antonio Rodrigo, David Jiménez and José Manuel Menéndez Universidad Politécnica de Madrid Las Vegas NV, 10th January 2015
- 2. Index • Problem description: Visual discomfort in 3D • Work methodology: Characterization of individual sequences Description of pairs of sequences Subjective quality assessment • Results and examples • Future work • Conclusions
- 3. Problem description (I) • The differences and variations in 3D Disparity may cause visual discomfort. • What is disparity in 3D video?
- 4. • Disparity may offer an incredible experience. • The eye focus the objects. Accommodation of the eyes needs enough time to adapt to changes for correct vision of 3D videos. Problem description (II)
- 5. Problem description (III) • If video sequences are not well controlled, especially in abrupt changes, which need fast converging process in the eye… What happens??
- 6. Problem description (IV) • The eye has not enough time to focus objects, discomfort, annoyance and, consequently, headache may occur. • Because convergence in 3D sequences is more complex than when contemplating bidimmensional video.
- 7. Problem description (V) • But… – How do we evaluate the reactions of human eye derived from abrupt changes when contemplating 3D video?
- 8. • Answer: – With subjective assessment showing the spectator pairs of sequences and analyzing the abrupt changes among us. – Knowing the variations between parallax diagrams is useful for this effect. Problem description (VI)
- 9. Examples of 3D disparity (I)
- 10. Examples of 3D disparity (II)
- 11. Work methodology Characterization of individual video sequences Sequence 1 Sequence 2 Combination of video pair sequences Sequence Motion Parallax Distribution 1 2 High variety of types of transitions Subjective assessment with pairs of sequences for transition analysis 3 Analysis of when visual discomfort happens4
- 12. Characterization of individual video sequences • Parallax diagrams – Ranges and variance of negative and positive parallax • Distribution of parallax in the image. • Values of Temporal (TI) and Spatial (SI) Information (also in 2D tests) – Motion (TI) – Spatial complexity and detail (SI)
- 13. Parallax and disparity diagram Visual distribution of parallax Parallax Histograms With the use of SAD techniques
- 14. Combination of video pair sequences – Analysis of types of changes or transitions between two 3D sequences. – Types of sequences transitions: • Combination of sequences with positive and negative parallax • Combination of sequences with higher or lower variance of negative/positive parallax • Combination of sequences with objects located in different / same regions of the image
- 15. Subjective assessment • Battery of tests with 3D high-definition video sequences • Annoyance 5-notes Scale for evaluating the transition between each pair of videos MOS Scale Annoyance derived from transition Quality of Experience 5 Very comfortable Excellent Experience 4 Comfortable Good Experience 3 Mildly uncomfortable No visual discomfort 2 Uncomfortable Visual discomfort 1 Extremely uncomfortable High visual discomfort Device Philips 65PFL9708S Resolution 3840 x 2160p Brightness 450 cd/m² Size 65” Widescreen Technology LED Ultra HD 3D Passive glasses
- 16. Example 1 • Transition 12: “Angel” to “Ladder” 40% of the people give a score that manifests visual discomfort
- 17. Example 2 • Transition 14: “Spaceship” to “Astronaut” Negative parallax in right side of first video to negative/positive combination
- 18. Example 3 • Transition 16: “Station” to “Itaca3d” This is the worst scored transition in the tests ↑↑Motion ↑↑Motion Hiperstereoscopy!
- 19. Example 4 • Transition 2: “Boxers” to “Dance” Negative parallax located in different areas, less annoyance for observers.
- 20. Example 5 • Transition 4: “Hall” to “Laboratory” Both videos with negative parallax in both videos and window violation → low scores. Window violation!
- 21. Conclusions (I) • Motion is a key element of production of visual discomfort, but it is not the only one. When it is combined with sequences with high negative parallax may generate visual discomfort. • If the negative parallax in hyperstereoscopy is located in different parts of the sequences in the transition, visual discomfort appears less than when located in same areas.
- 22. Conclusions (II) • Fast variation of negative parallax is usually the main source of visual discomfort, especially when the transition is produced to a content with a completely different disparity diagram. • Only hyperstereoscopy (i.e. pixels with negative parallax with disparities higher than 5) in the sequence is not enough for detecting visual discomfort, it is the transition what provokes the discomfort.
- 23. Future work • After detecting the main sources of visual discomfort… Developing recommendations and guidelines for 3D contents creators. Generating tools for automatic detection of discomfort in 3D videos.
- 24. Thanks for your attention!!