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Advanced Mechanisms for Delivering High-Quality Digital Content

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In this paper, a practical solution for optimal coding parameters using different bandwidth requirements is presented. The obtained specification is based on the analysis of a large database of more than 10,000 sequences compressed with different parameters. The obtained parameters can be used both for adaptive streaming or storage optimization.

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Advanced Mechanisms for Delivering High-Quality Digital Content

  1. 1. Advanced Mechanisms for Delivering High-Quality Digital Content Mikołaj Leszczuk and Lucjan Janowski
  2. 2. Presentation outline Conclusions Results Methods Background
  3. 3. Conclusions
  4. 4. Current H.264 video codec mechanism SouRCe video sequence (SRC) Codec • Bit-rate • Quantization Parameter (QP) Processed Video Sequence (PVS)
  5. 5. What is the problem? • Limited coding parameters considered: • Currently mainly: • Bit-rate • QP • 10+ more to be considered • Same parameters for all video sequences, while more detailed content analysis possible using indicators like: • Temporal Activity (TA) • Spatial Activity (SA) • Blur • … • How to map indicators onto coding parameters?
  6. 6. Methods
  7. 7. Video Quality Experts Group • And here comes VQEG … • Vision: “To advance the field of video quality assessment...” • International experts: industry, academia, governmental, standard-developing • VQEG’s Joint Effort Group (JEG) • More information: http://www.vqeg.org/
  8. 8. Proposed H.264 video codec mechanism SRC Analysis • SA • TA • Blur • … Codec • Bit-rate • QP • 10+ parameters • … PVS
  9. 9. What is our solution? Selecting SRC test-set Selecting number of codec parameters (Hypothetical Reference Circuits, HRC) Employing super- computer cluster to get encoded (PVS) videos Using existing well- established objective quality metrics for ground-truth Tuning results with subjective crowdsourcing and in- lab experiments Analysing indicators Get mapping Developing codec considering quality factors
  10. 10. Selecting SRC • 10×1080p@25 SRC • Selected from VQEG resources • Covering many different features: • Natural and synthetic • Professionally shot and user generated • Video content 
  11. 11. Selecting HRC (1/2) Basic compression Temporal & spatial changes Time prediction I, B, P frame size factors Bit-rate 1, 2, 4, 8, 16 Mbit/s QP 26, 32, 38, 46 GOP length 8, 16, 32, 64 32, 64 Number of B frames 0, 2, 3, 7 2 B-pyramid strict, none none Frame rate 25 8, 12 25 Resolution 1920×1080 960×540, 480×270 1920×1080 Integer pixel motion estimation method default dia, esa, umh default Maximum motion vector search range default 4, 64 default Number of reference frames default 4,16 default Number of slices per frame 1, 2 1 I to P frame ratio default 0.8, 1, 1.2, 1.4 P to B frame ratio default 0.5, 0.8, 1, 1.2, 1.4
  12. 12. Selecting HRC (2/2) Approximately 1300 distinctive codec parameters!
  13. 13. Getting PVS (1/2) • Pre-processing: • Source AVI format using YCbCr space with 422 sampling • Sub-sampled with Lanczos to 420 sampling • Two well-known encoders: JM and x264 • Post-processing: decompression, destination AVI format
  14. 14. Getting PVS (2/2) Approximately 13,000 distinctive PVS!
  15. 15. Analysis PVS with quality metrics • Quality metrics used and inter-checked: • Peak Signal-to-Noise Ratio (PSNR) • Structural Similarity Index (SSIM) • Video Quality Metric (VQM) • Visual Information Fidelity (VIF) • VQM shown to be best FR metric • Fit factor of subjective data higher than other metrics by ≥20% • Therefore VQM metric used for further analysis of obtained results
  16. 16. Analysing indicators • Video indicators analysed: TA, SA, and Blur • More details on experiment reported in: Leszczuk, M. et al., “Freely available large-scale video quality assessment database in full-HD resolution with H.264 coding,” IEEE GLOBECOM 2013
  17. 17. Results
  18. 18. Getting mapping Given video sequence Required compression rate Best codec parameters
  19. 19. Proof-of-Concept • Developed advanced codec mechanism • Supporting streaming on 5 popular browsers : • Google Chrome (native support for HTML5/H.264) • Mozilla Firefox (temporary solution) • Microsoft Internet Explorer (temporary solution) • Apple Safari (temporary solution) • Opera (temporary solution) • Plug-ins as temporary solutions: • Windows Media Player (WMP) plug-in for Windows • VideoLAN Client (VLC) for Linux and OS X
  20. 20. Integrated technologies FFmpeg Decoding video input (169 codecs) x264 Parameterised compression itself Matroska Multimedia container
  21. 21. Tested solution Multimedia container file inputs Encoding formats as file input Quality models Erroneous input data
  22. 22. Conclusions
  23. 23. Resources available at http://vq.kt.agh.edu.pl Video databases Quality metrics Research papers Other stuff

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