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Representation Switch Smoothing for Adaptive HTTP Streaming

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Presentation of the paper at the 4th International Workshop on Perceptual Quality of Systems (PQS 2013), Vienna, Austria, September 2013.

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Representation Switch Smoothing for Adaptive HTTP Streaming

  1. 1. REPRESENTATION SWITCH SMOOTHING FOR ADAPTIVE HTTP STREAMING Michael Grafl and Christian Timmerer 4th International Workshop on Perceptual Quality of Systems (PQS 2013), September 2-4 2013, Vienna, Austria M. Grafl and C. Timmerer 1Representation Switch Smoothing
  2. 2. OUTLINE  Introduction & Concept  Implementation Options  Evaluation & Results  Discussion  Conclusions M. Grafl and C. Timmerer Representation Switch Smoothing 2
  3. 3. INTRODUCTION  DASH: Dynamic Adaptive Streaming over HTTP  Client downloads segments sequentially in best fitting representation (quality, resolution, frame rate)  Dynamically switch between representations (e.g., based on available bandwidth)  Representation switches annoying to viewers  How to reduce the quality impact of representation switches? M. Grafl and C. Timmerer Representation Switch Smoothing 3
  4. 4. CONCEPT  Avoid abrupt quality switches  Smooth transition between representations M. Grafl and C. Timmerer Representation Switch Smoothing 4 Representations min bitrate & quality max bitrate & quality Time Abrupt change of playback quality Representations min bitrate & quality max bitrate & quality Time Original quality of segment Smooth transition between representations
  5. 5. IMPLEMENTATION OPTIONS  Pre-decoder  Remove picture fidelity data (transform coefficients) before the decoder  Suitable for Scalable Video Coding (SVC)  Causes motion compensation drift  In-decoder  Remove picture fidelity data inside the decoder  Less drift but decoder-dependent  Post-decoder  Post-processing filter mimicking distortion  No drift  Coding format independent M. Grafl and C. Timmerer Representation Switch Smoothing 5
  6. 6. IMPLEMENTATION OPTIONS  In-decoder implementation option for SVC M. Grafl and C. Timmerer Representation Switch Smoothing 6 Motion Compen- sation Inverse Quanti- zation Inverse Quanti- zation Inverse Trans- form Decoded Picture Buffer Predict- ion Data Base Residual Enhance- ment Layer Residual + + + + Decoded Frame Motion Compen- sation Inverse Quanti- zation Inverse Quanti- zation Inverse Trans- form Decoded Picture Buffer Predict- ion Data Base Residual Enhance- ment Layer Residual Decoded Frame + + + + Inverse Trans- form + + Representation Switch Smoothing
  7. 7. EVALUATION  Subjective evaluation of down-switching scenario  2 test sequences (15 sec, from TearsOfSteel, 1280x720, H.264, no sound)  Quality Switching (after 10 sec) vs.  Representation Switch Smoothing (5-sec transition)  18 participants  Pair-wise comparison (may repeat versions)  Rating: Version a, Version b, No difference  Smoothing simulated through repeating full-sequence encoding and extraction of relevant frame  Issue: temporal noise due to moving blocking artifacts M. Grafl and C. Timmerer Representation Switch Smoothing 7
  8. 8. EVALUATION  Per-frame PSNR for test sequences M. Grafl and C. Timmerer Representation Switch Smoothing 8 high motion low motion
  9. 9. SCREENSHOTS M. Grafl and C. Timmerer Representation Switch Smoothing 9 Sequence 1 Sequence 2
  10. 10. RESULTS M. Grafl and C. Timmerer Representation Switch Smoothing 10 Preferred Version Sequence Quality Switching Representation Switch Smoothing No Difference Sequence 1 5 7 6 Sequence 2 3 12 3
  11. 11. DISCUSSION  Representation Switch Smoothing: significant improvement for Sequence 2 (low-motion)  Temporal noise may have impacted results  Longer transitions (e.g., 10 sec) may improve QoE  Possible influence factors:  Base quality, bitrate difference, cuts, resolution, spatio- temporal complexity, duration of low quality  Alternative approach: limited steps below just-noticeable difference M. Grafl and C. Timmerer Representation Switch Smoothing 11
  12. 12. CONCLUSIONS  Idea: reduce annoyance of abrupt quality switches by a smooth transition  Avoid viewer distraction in adaptive HTTP streaming  Implementation options discussed  Subjective evaluation for down-switching  Possible influence parameters identified  Future work:  Improve implementation (avoid temporal noise)  Analyze impact of influence parameters  Evaluated up-switching scenario M. Grafl and C. Timmerer Representation Switch Smoothing 12
  13. 13. THANKS FOR YOUR ATTENTION! Questions? M. Grafl and C. Timmerer Representation Switch Smoothing 13 http://itec.aau.at/~mgrafl | @MyKey_ – http://aau.at/tewi/inf/itec/mmc/ | @itecMMC

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