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Quality Assessment for Digital Cinema: Test Materials & Metrics for Compression

Quality Assessment for Digital Cinema: Test Materials & Metrics for Compression. Charles Fenimore Convergent Information Systems Division, NIST Digital Cinema 2001 Conference January 12, 2001. Quality Assessment. Tests - subjective and objective

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Quality Assessment for Digital Cinema: Test Materials & Metrics for Compression

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  1. Quality Assessment for Digital Cinema: Test Materials & Metrics for Compression Charles Fenimore Convergent Information Systems Division, NIST Digital Cinema 2001 Conference January 12, 2001

  2. Quality Assessment • Tests - subjective and objective • Display matters in compression tests - strategy for complex systems • Video and cinema: materials and metrics • Conclusions

  3. Quality measurement in video • Compression in digital cinema. • Subjective testing is the gold standard, • objective testing is a useful adjunct • Selection of test materials • Qualification of the test system • Test methods smorgasbord: ITU-R Rec 500

  4. Goals of Testing • Characterize for a range of typical materials • OR • Stress the system, to see where it breaks • Compression or decompression testing. • Threshold vs. Wide Range Tests.

  5. Qualifying the system • Resolution and sharpness. • Spot-size: trade flicker for resolution • Motion rendition and flicker, image stability • Dynamic range, tone • Brightness and contrast • Viewer background: golden eyes/naive • Visual acuity of the viewers

  6. SMPTE RP 133 – resolution pattern

  7. Selection of subjective test materials • Desired attributes include a range of: • resolution and detail patterns, • image and camera motion, • luminance, • color saturation and hue, • skin tones, • noise, and • graphics and titles. • A sense of presence, reality, and depth.

  8. Skin Tones

  9. Selection of subjective test materials • Experience with DV provides surprises in coding difficulty. • Range of image detail, motion, color and luminance. • Criticality: a computable measure of image detail and motion in electronic imagery.

  10. Surprisingly tough to compress

  11. Synthetic test patterns • Used in engineering evaluation of imaging systems. • SMPTE color bars, other color patterns • SMPTE Rec. 133 Resolution Chart. • Sarnoff, AT&T, many other contributors • NIST spinning wheel (blocking) and moving spirals (mosquito noise) patterns.

  12. Impairment specific detectors • FLAT: • an 8  8 block of pixels having constant luma, Y'0, inside the block in either row, column, or both directions and • at least one pixel exceeds a threshold value, T, across the block boundary. • Detect those flats with high local contrast ---

  13. Conclusions • There is a need for both subjective and objective metrics & materials for imaging system evaluation. • Properly designed d-cinema testing: • Know your users, what are needs and goals. • Translate user needs to engineering requirements (subjective and objective criteria, resolution and sharpness, color characteristics), • Specify measurement protocol to test requirements: metrics and materials.

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