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Perceived Quality for Transported Video

Perceived Quality for Transported Video. Nele Van den Ende Reinder Haakma Maddy Janse Peter van der Stok. Overview. Background Adaptation Methods I-Frame Delay Signal-to-Noise Ratio Scalability Research Categories Perception Experiments Method Design Results Summary

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Perceived Quality for Transported Video

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

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

  3. Background Access to content, anywhere, anytime

  4. Background But there are disturbance problems…

  5. 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. MPEG Induced Effects

  7. MPEG Induced Effects

  8. Outgoing packets Incoming packet C W W W W W W S S S S S IFD queue Adaptation MethodsI-Frame Delay • Network clogging & buffer overflow drop frames with least importance • Two parts: tagger & dropper

  9. Adaptation MethodsSignal-to-Noise Ratio Scalability • Dividing video in layers: one base-layer, several possible enhancement layers

  10. Research Categories • Compressing methods • Adaptation methods • User perceived errors

  11. Perception ExperimentsMethod • Double-stimulus continuous quality-scale • 10 sec video sequences • 1 hour per observer

  12. Perception ExperimentsDesign • 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. Perception ExperimentsQuestions - 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. Perception ExperimentsResults - IFD

  15. Perception ExperimentsQuestions – 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. Perception ExperimentsResults – SNR Scalability

  17. Summary • Saturation effect • when perceived quality is already low/high, observers don’t 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. Future Research Questions • Influence of the content’s type semantic versus physical appearance? predictability versus unpredictability? • Management of the disturbances or the type of perceived disturbances? • What about audio?

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