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Understanding Perceived Video Quality in Transported Content: Research Insights

This research explores the perceived quality of transported video, focusing on encoding, adaptation methods, and the impact of I-Frame delay and signal-to-noise ratio. It investigates how these factors influence viewer experiences through perception experiments, examining bitrate differences, scene contents, and duration of quality drops. The findings reveal that while B-frame loss is subtle, it significantly affects viewer perception, and the saturation effect influences how quality changes are detected. Future research aims to delve deeper into content type and disturbance management.

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Understanding Perceived Video Quality in Transported Content: Research Insights

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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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