Perceived Quality for Transported Video Nele Van den Ende Reinder Haakma Maddy Janse Peter van der Stok

2 Research Overview Background Adaptation Methods –I-Frame Delay –Signal-to-Noise Ratio Scalability Research Categories Perception Experiments –Method –Design –Results Summary Future Research Questions

3 Research Background Access to content, anywhere, anytime

4 Research Background But there are disturbance problems…

5 Research MPEG Encoding Compress video Play back platforms Types of frames –Intra-coded, predictive-coded & bi-directionally predictive coded Groups of Pictures I B B P B B P B B

6 Research MPEG Induced Effects

7 Research MPEG Induced Effects

8 Research Adaptation Methods I-Frame Delay Network clogging & buffer overflow drop frames with least importance Two parts: tagger & dropper IFD queue SSSSWWWW Outgoing packets C Incoming packet SWW

9 Research Adaptation Methods Signal-to-Noise Ratio Scalability Dividing video in layers: one base-layer, several possible enhancement layers

10 Research Research Categories Compressing methods Adaptation methods User perceived errors

11 Research Perception Experiments Method Double-stimulus continuous quality-scale 10 sec video sequences 1 hour per observer

12 Research Perception Experiments Design Bitrate: 6 vs. 3 Mbps Scenes: Matrix - Reloaded vs. Feet of Flames Duration of loss: 2 vs. 4 vs. 8 sec IFD: 1/7 vs. 1/14 B-frame loss SNR: 1/3 vs. 2/3 base-layer

13 Research Perception Experiments Questions - IFD Is leaving out more B-frames (compared to leaving out less B-frames) perceived as worse quality? Does the duration of a quality drop influence perceived video quality? Do observers notice the difference between the shown bit-rates?

14 Research Perception Experiments Results - IFD

15 Research Perception Experiments Questions – SNR Scalability Does the duration of a quality drop influence perceived video quality? Does a quality saturation effect really show? Do observers really not notice when video quality is enhanced once a certain level is reached? Do observers notice the difference between the shown bit-rates?

16 Research Perception Experiments Results – SNR Scalability

17 Research Summary Saturation effect –when perceived quality is already low/high, observers dont notice further decreasing/increasing of the objective quality –thresholds depend on scene content IFD –effects were small, but B-frame loss was small –influence of duration and amount of quality loss depends on scene content and bit-rate –B-frame loss is more pronounced and lasts longer differences between reference and modified video sequences seem easier to detect SNR –observers perceive the different bit-rates of the base-layers –extent depends on scene content and duration of the quality drop

18 Research Future Research Questions Influence of the contents type semantic versus physical appearance? predictability versus unpredictability? Management of the disturbances or the type of perceived disturbances? What about audio?