Disparity may cause visual discomfort. Pairs of video sequences with different levels of parallax, both negative and positive, were presented together to the observers. The observers evaluated the cases in which visual discomfort occurred after visualizing the transition on each pair

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!!