Visual and technical quality control
   for high definition television

                                       16/1



   ...
Overview

Video quality control in a filebased world
Impact of HDTV emergence on quality control
Video quality evaluation
...
Video quality control in a filebased world

AudioVisual Quality Control
  ! Audio
  ! Video
  ! Interaction between audio ...
VRT-medialab: onderzoek en innovatie
Video quality control in a filebased world

Technical quality control
  ! Container
  ! Metadata
  ! Interaction between c...
VRT-medialab: onderzoek en innovatie
Video quality control in a filebased world

Automated QC




 VRT-medialab: onderzoek en innovatie
Video quality control in a filebased world
                                                    Application Specs      DV-2...
Video quality control in a filebased world

Application specification
validation report




  VRT-medialab: onderzoek en i...
Video quality control in a filebased world

Safeguarding audiovisual quality
  ! Maintaining quality throughout the produc...
Impact of HDTV emergence on quality control

Proliferation of raster formats
                     SD TV                   ...
Impact of HDTV emergence on quality control

Proliferation of codecs
                                                     ...
Impact of HDTV emergence on quality control

Viewer quality expectation
  ! Consumer expects ROI from flat panel investmen...
Video quality evaluation




VRT-medialab: onderzoek en innovatie
Video quality evaluation
Video sequence used for testing
(source EBU) :
  ! High quality source material
  ! 10-bit YCBCR ...
Note on viewing conditions

Expert evaluation :
  ! Class 1 reference monitor @ 1H, 3H
  ! High quality consumer device (F...
Video quality in production chain

Simulation chain




                                            without
              ...
Video quality in production chain

  Codecs tested :
    ! Camera : AVC-I, DVCProHD, XDCAM HD422
    ! PostProduction : DN...
Video quality in production chain

   Test setup




Sony PDW-HD1500* Panasonic AJ-HPM110** Avid Airspeed + DNXchange
  XD...
Video quality in production chain

Test setup



                Encode                    Decode



           HD-SDI    ...
Video quality evaluation

Evaluation methods :

 ! Objective tests


 ! Subjective tests


 ! Automated subjective tests

...
Video quality evaluation

 Objective tests : PSNR, SSIM, ...

                 1 mquot;1 n quot;1                         ...
Video quality evaluation

Objective tests : PSNR, SSIM, ...




                  Advantages                              ...
Video quality evaluation

Subjective tests : DSCQS, TSCES, ...




  VRT-medialab: onderzoek en innovatie
Video quality evaluation
                                        Upper anchor
                                       Sourc...
Video quality evaluation

      Subjective tests :
   DSCQS, TSCES, ...




               Advantages                     ...
Video quality evaluation

   Automated subjective tests : Tektronix PQA-500, Opticom PEVQ Analyzer, ...
      ! Aims to pr...
Video quality evaluation

Expert viewing
  ! Aim :
          – Visually evaluate video quality
          – Determine typic...
Video quality in production chain

Expert viewing (“The proof of the pudding is in the eating”)




  VRT-medialab: onderz...
Video quality in production chain

Uncompressed vs Compressed video material




  VRT-medialab: onderzoek en innovatie
Video quality in production chain

Compressed vs Compressed video material




  VRT-medialab: onderzoek en innovatie
Video quality due to de-interlacing
source                                            de-interlaced


         De-interlac...
Video quality in distribution chain




VRT-medialab: onderzoek en innovatie
Distribution encoder

Distribution encoder = device that compresses the broadcaster’s signal into
a format suitable for tr...
Distribution encoder: bit-rate




                                                                      AVC/DNxHD – 16Mbi...
Distribution encoder and production codec

Uncompressed HD ~ 1 500 Mbit/s
Production bitrate ~ 100 Mbit/s
Distribution enc...
Distribution: the end of the chain

Receiver (set-top-box)
  ! Interlacing – de-interlacing
  ! Scaling
Television
  ! A l...
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Visual and technical quality control for high definition television

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Visual and technical quality control for high definition television

  1. 1. Visual and technical quality control for high definition television 16/1 Tom Beckers Wim Ermens
  2. 2. Overview Video quality control in a filebased world Impact of HDTV emergence on quality control Video quality evaluation Production chain simulation Broadcast chain simulation VRT-medialab: onderzoek en innovatie
  3. 3. Video quality control in a filebased world AudioVisual Quality Control ! Audio ! Video ! Interaction between audio and video : e.g. lipsync File based AV Quality Control ! Part of an automated or manual workflow – Diagnose – Repair / Redo VRT-medialab: onderzoek en innovatie
  4. 4. VRT-medialab: onderzoek en innovatie
  5. 5. Video quality control in a filebased world Technical quality control ! Container ! Metadata ! Interaction between container, audio and video : e.g. duration of tracks File based technical quality control ! Part of an automated or manual workflow ! Application specifications VRT-medialab: onderzoek en innovatie
  6. 6. VRT-medialab: onderzoek en innovatie
  7. 7. Video quality control in a filebased world Automated QC VRT-medialab: onderzoek en innovatie
  8. 8. Video quality control in a filebased world Application Specs DV-25 (News) D-10 (APP) HD Contribution MXF analysis & application Production specification validation Play-out Archive Application Specification IRT MXF Analyzer MXF MXF file Validator analysis Ardendo CheckMXF MXF analysis report VRT-medialab: onderzoek en innovatie
  9. 9. Video quality control in a filebased world Application specification validation report VRT-medialab: onderzoek en innovatie
  10. 10. Video quality control in a filebased world Safeguarding audiovisual quality ! Maintaining quality throughout the production chain – Choose material as close to source as possible – prevent unneeded multi-generation – Try to produce with the shortest/’most apt’ chain – Prevent unneeded multi-generation – Prevent transcoding 720p 720p 720p ! 1080p ! 1080i ! – Check quality 1080p Black Box 720p 1080i ! Carefully design the production chain (in production/broadcast – Choose the right codecs 1080i 1080i ! chain) 1080p! 720p ! 1080i – Choose the right equipment 1080p 720p 1080i VRT-medialab: onderzoek en innovatie
  11. 11. Impact of HDTV emergence on quality control Proliferation of raster formats SD TV HD TV 1080p25 PAL 576i50 720p50 1080i50 1080p50 VRT-medialab: onderzoek en innovatie
  12. 12. Impact of HDTV emergence on quality control Proliferation of codecs HDV 50 Mbps ProRes Dirac JPEG2K 10 bit sampling 4:2:2 4:4:4 YUV HDCAM-SR XDCAM HD42 DVCProHD 180Mbps 440Mbps 100Mbps DNxHD HDCAM RGB 4:2:0 / 4:1:1 SVC AVC-Intra 8 bit sampling XDCAM HD AVCHD VRT-medialab: onderzoek en innovatie
  13. 13. Impact of HDTV emergence on quality control Viewer quality expectation ! Consumer expects ROI from flat panel investment ! Depends on content type (drama, news, sports, soap) What codec to choose? ! Picture quality ! quality evaluation needed ! Bit rate ! Performance ! Support ! Scalability VRT-medialab: onderzoek en innovatie
  14. 14. Video quality evaluation VRT-medialab: onderzoek en innovatie
  15. 15. Video quality evaluation Video sequence used for testing (source EBU) : ! High quality source material ! 10-bit YCBCR samples ! Chroma subsampling 4:2:2 ! HD-SDI compatible ! 720p50 VRT-medialab: onderzoek en innovatie
  16. 16. Note on viewing conditions Expert evaluation : ! Class 1 reference monitor @ 1H, 3H ! High quality consumer device (FullHD, Plasma) @ 1H, 3H Present demo setup ! Overhead projector (internal processing?) ! Not sufficiently dark room ! Sub ideal circumstances Interested parties : ask for demo in better circumstances... VRT-medialab: onderzoek en innovatie
  17. 17. Video quality in production chain Simulation chain without pixelshift with pixelshift (+2H, +6V) Camera Post production encoding encoding (4 generations) VRT-medialab: onderzoek en innovatie
  18. 18. Video quality in production chain Codecs tested : ! Camera : AVC-I, DVCProHD, XDCAM HD422 ! PostProduction : DNxHD, AVC-I, DVCProHD, XDCAM HD422 Codec properties Codec Bitrate Chroma Sample GOP Spatial subsampling (Mbps) subsampling size (bits) AVC-I 100 4:2:2 10 I frames only None DVCProHD 100 4:2:2 8 I frames only 3:4 horizontal : 960 luma samples/line DNxHD 115 4:2:2 8 I frames only None XDCAM 50 4:2:2 8 LongGOP None HD422 (n=12 @ 720p) VRT-medialab: onderzoek en innovatie
  19. 19. Video quality in production chain Test setup Sony PDW-HD1500* Panasonic AJ-HPM110** Avid Airspeed + DNXchange XDCAM HD422 DVCProHD DNxHD AVC-I * test model provided by Sony Belgium ** test model provided by Panasonic Belgium VRT-medialab: onderzoek en innovatie
  20. 20. Video quality in production chain Test setup Encode Decode HD-SDI HD-SDI Uncompr. Gen 0 Gen 1 Gen 2 Gen 3 Gen 3 Gen 4 source (Cam) (PP1) (PP2) (PP3) shifted (PP4) Uncompressed YCbCr storage HD-SDI ingest & playout VRT-medialab: onderzoek en innovatie
  21. 21. Video quality evaluation Evaluation methods : ! Objective tests ! Subjective tests ! Automated subjective tests ! Expert viewing VRT-medialab: onderzoek en innovatie
  22. 22. Video quality evaluation Objective tests : PSNR, SSIM, ... 1 mquot;1 n quot;1 MAX R MSE frame = !! R(i, j ) quot; I (i, j ) 2 PSNR frame = 20 ! log10 ( mn i =0 j =0 MSE frame Reference Impaired Squared difference VRT-medialab: onderzoek en innovatie
  23. 23. Video quality evaluation Objective tests : PSNR, SSIM, ... Advantages Disadvantages objective 3 resultsets per sequence (Y, Cb, Cr) reproducible unsensitive to grouping of pixel automated test differences VRT-medialab: onderzoek en innovatie
  24. 24. Video quality evaluation Subjective tests : DSCQS, TSCES, ... VRT-medialab: onderzoek en innovatie
  25. 25. Video quality evaluation Upper anchor Source material Material to be evaluated Lower anchor Worst case (D)MOS scores VRT-medialab: onderzoek en innovatie
  26. 26. Video quality evaluation Subjective tests : DSCQS, TSCES, ... Advantages Disadvantages closest to real life experience difficult to test many sequences timeconsuming to setup difficult to get sufficient statistics worst case reference definition VRT-medialab: onderzoek en innovatie
  27. 27. Video quality evaluation Automated subjective tests : Tektronix PQA-500, Opticom PEVQ Analyzer, ... ! Aims to provide (D)MOS score ! Simulate : – Monitor setup and characteristics – Viewing setup and conditions – Viewer setup and characterisics – Human visual system (= tricky) Advantages Disadvantages automated test good correlation to subjective test results to be proven closer correlation to subjective test sults than PSNR typically slower than objective tests no worst case reference mandatory VRT-medialab: onderzoek en innovatie
  28. 28. Video quality evaluation Expert viewing ! Aim : – Visually evaluate video quality – Determine typical artefacts – Compare source with test material – Compare test material with other test material ! Method : – Create splitscreen images – Evaluate on (reference) monitor – Create ranking from intercomparison VRT-medialab: onderzoek en innovatie
  29. 29. Video quality in production chain Expert viewing (“The proof of the pudding is in the eating”) VRT-medialab: onderzoek en innovatie
  30. 30. Video quality in production chain Uncompressed vs Compressed video material VRT-medialab: onderzoek en innovatie
  31. 31. Video quality in production chain Compressed vs Compressed video material VRT-medialab: onderzoek en innovatie
  32. 32. Video quality due to de-interlacing source de-interlaced De-interlacing: difficult to perform Good quality -converters exist (price!) 720p DNxHD (Gen0) 1080i - DNxHD (Gen0) – de-interlace – 720p VRT-medialab: onderzoek en innovatie
  33. 33. Video quality in distribution chain VRT-medialab: onderzoek en innovatie
  34. 34. Distribution encoder Distribution encoder = device that compresses the broadcaster’s signal into a format suitable for transmission/distribution Codecs: MPEG-2 or MPEG-4 H.264 (tested) Interfaces: HD-SDI quot; ASI Typical bitrate in/out: ! From 50-200 Mbit/s quot; 10 Mbit/s (or less) Parameters: ! Encoding delay ! Encoder bit-rate ! Profile/Noise reduction/GOP size/… VRT-medialab: onderzoek en innovatie
  35. 35. Distribution encoder: bit-rate AVC/DNxHD – 16Mbit/s H.264 Which bit-rate to choose? Uncompressed ! Distribution channel ‘defines’ available bit-rate ! MPEG-4 does a fine job ! Motion in video is important AVC/DNxHD – 8Mbit/s H.264 AVC/DNxHD – 10Mbit/s H.264 VRT-medialab: onderzoek en innovatie
  36. 36. Distribution encoder and production codec Uncompressed HD ~ 1 500 Mbit/s Production bitrate ~ 100 Mbit/s Distribution encoder ~ 10 Mbit/s Do we actually see the influence of the production codec? AVC/AVC + 8 Mbit/s H.264 DVC/DVC + 8 Mbit/s H.264 VRT-medialab: onderzoek en innovatie
  37. 37. Distribution: the end of the chain Receiver (set-top-box) ! Interlacing – de-interlacing ! Scaling Television ! A lot of choice ! De-interlace ! Scale ! Process (sharpen – noise reduction) Make sure there’s no unnecessary signal conversion VRT-medialab: onderzoek en innovatie

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