Cni mc donough_preservation


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  • Comments courtesy of Marco Solorio, One River Media: NTSC Color Bars - These colors were taken from Final Cut Pro 3. It's nice to see how well these codecs keep their color integrity to the time old standard color bars. Also look between the color bars and you'll notice edges combining and smearing colors together in some codecs. Parking Meter - This somewhat represents what a true-life camera shot would look like. The top of the handle also makes for a good shadow test. In some codecs, detail is lost in most of the parking meter image. Chroma Text - Under most situations, a compressed color space of 4:2:2 will yield less than desirable results with a test like this. The text simply can't hold up to the chroma value of the bluish background color. Luma Text - More often than not, a luminance test like this will favor well. Only poor codecs will fail this test. Color Filtering - Ah, one of the best tests by far. This shows how much the codec is color filtering the image. Some codecs lose this test altogether by changing part of the red aliased line to gray. The key is to enlarge the image after you render it so you can really see the effect of color filtering. The dynamic image selection below shows the different codec's color filtering side by side. Note that the image has been enlarged 300% using "Nearest Neighbor" instead of the default "Bicubic" so Photoshop does not interpolate new, colored pixels. Thanks to Matt Silverman for leading me on to this little, but powerful test. Gradient Banding - This is where all of this started! It was initially due to banding that made me first look into testing different uncompressed codecs. Back in my Media 100 days, banding was something you had to deal with. But with a new NLE purchase in mind, I wanted to see which uncompressed NLE did away with this age-old problem. For this test, I created a solid layer in Adobe After Effects. I added a Mandelbrot color fractal and blurred it out with a value of 120. The colors slowly change over time to give codecs like MPEG and Cinepak a tough time with spatial interpolation. As for the gradient, some codecs just can't handle it and banding is a result. RGB Bars - To get a good effect of color filtering (or lack there of) combined with the color space limitation of YUV video, pure red, green and blue colors are used and placed at a slant. If the bars were perfectly straight, then the effect may not produce large enough blocking. Some codecs have larger blocking in this area than others, even in the same color space. RGB Bull's Eye - Pure RGB circles are stacked upon each other to see how much the colors smear into each other. In most cases, the blue and green circles stack up okay, but the red circle usually becomes aliased. Single Pixel Lines - A test to see how well a codec can accurately encode single pixel lines of differing colors. Notice also that the green line is slightly off the background green color. Makes for interesting results. Compared to hair, these lines are thick. Color Grid - Using a grid of lines that are both 1-pixel and 2-pixel in width, we can see how much color smear a codec may produce. This test can also show the relationship between the grid's lines and a codecs compression block structure (like a highly compressed Motion JPEG render). Random Noise - The black and white noise test will typically fair well (sometimes perfect) for the 4:2:2 uncompressed bunch. The color noise test however can't replicate perfectly even by the best 4:2:2 uncompressed codec... the colors simply smear out due to the compressed color space limitation. Interlace - This test represents the effect of compression interacting with interlaced fields. If there is a lot of compression or color space artifacts, then this can result in messy interlace lines, which could result in flickery playback. RGB Circles - Much like the "Bull's Eye" test, this test shows how color space blocking can affect an RGB area that is not constant (unlike the RGB bars that are constant). Simple Color Spectrum - This spectrum is a little like the other color spectrum, except that this spectrum has 30-pixel high lines that should stay constant. If a codec contours, then what should be a 30-pixel high color will become many colors. Grayscale Ramp - Exactly like the Simple Color Spectrum, but with monochromatic values. A good codec will replicate all the pixels in this ramp. Some codecs however, induce coloring in these pixels. HSL Spectrum - Although there isn't enough area in this image to display all the colors in an HSL spectrum, it does give us a good idea of any color changes or contouring. 16-bit Ramp - This test is really only useful for 10-bit or higher codecs. To the far left of the red ramp is a 16-bit RGB value of [32768,0,0] and to the far right of the ramp is a 16-bit RGB value of [32768,257,257]. In 8-bit fashion, this is only a difference of a couple RGB values, whereas in 16-bit mode, it's a difference of a few hundred RGB values. Seeing how well a codec can represent these microscopic changes is a true test to its replication accuracy.
  • For uncompressed case, we assume 141.5 GB for video + another 1.5 GB for 48 KHz 24-bit stereo audio for a single master MPEG4 streams are assumed to be 5 mbps and 0.5 mbps.
  • Assoc. for Information & Image Management 10-year projection of disk prices
  • Cni mc donough_preservation

    1. 1. Preservation-Worthy Digital Video: Hope You Brought Your Checkbook Jerome McDonough New York University June 2, 2011
    2. 2. Digital Video Basics <ul><li>A video signal consists of luminance and chrominance information </li></ul><ul><li>Luminance – brightness, varying from white to black (abbreviated as Y) </li></ul><ul><li>Chrominance – color (hue & saturation), conveyed as a pair of color difference signals: </li></ul><ul><ul><li>R-Y (hue & saturation for red, without luminance) </li></ul></ul><ul><ul><li>B-Y (hue & saturation for blue, without luminance) </li></ul></ul>
    3. 3. Digital Video Basics <ul><li>Where’s the green? </li></ul><ul><li>Spectral response of the human eye peaks in the green frequencies. The perceived brightness of an item can be constructed using weighted values for its red, green and blue components: </li></ul><ul><ul><li>Y = 0.299 R + 0.587 G +0.114 B , or </li></ul></ul>
    4. 4. Digital Video Basics 4:2:2 sampling 4:2:0 sampling 4:1:1 sampling 4:2:2 – High End DV (Digital Betacam, DVCPro50) 4:2:0 – MPEG 1 & 2 4:1:1 – DV and DVCAM
    5. 5. Digital Video Basics <ul><li>Why not 4:4:4 sampling? </li></ul><ul><ul><li>720 x 486 resolution = 349,920 pixels per frame </li></ul></ul><ul><ul><li>349,920 pixels x 10 bits/sample x 3 samples/pixel = 10,497,600 bits per frame </li></ul></ul><ul><ul><li>10,497,600 bits/frame X 29.97 frames/second = 314,613,072 bits per second </li></ul></ul><ul><ul><li>314,613,072 bps x 3600 seconds = ~141.58 GB/hour </li></ul></ul><ul><ul><li>For 1920x1080 HDTV, more like 840 GB/hour </li></ul></ul><ul><li>4:2:2 sampling drops that rate by a third with almost no perceptible difference in quality. 4:2:0 and 4:1:1 drop it in half. </li></ul>
    6. 6. Digital Video Basics <ul><li>MPEG 2 Compression </li></ul><ul><ul><li>Further subsampling </li></ul></ul><ul><ul><ul><li>down sample to 8 bits/sample </li></ul></ul></ul><ul><ul><ul><li>down sample to 4:2:0 sampling regime </li></ul></ul></ul><ul><ul><li>Discrete Cosine Transformation + Requantizing of coefficients from DCT </li></ul></ul><ul><ul><li>Variable Length Encoding & Run Length Encoding </li></ul></ul><ul><ul><li>Interframe compression (motion compensation) </li></ul></ul><ul><li>all of which can take a 209 mbps video rate (for 4:2:2 video) and reduce it to around 8 mbps with no apparent visual loss. </li></ul>
    7. 7. Digital Video Basics <ul><li>Raw digital video is extremely storage and bandwidth intensive. </li></ul><ul><li>As a result, almost all digital video processing systems employ a mix of lossless and lossy compression mechanisms. </li></ul>
    8. 8. Preservation-Worthy Digital Video <ul><li>Desired characteristics for digital video we feel we can preserve include: </li></ul><ul><ul><li>Content can be migrated to new formats and new media without introducing artifacts </li></ul></ul><ul><ul><li>Stored in non-proprietary, standard format which is openly documented </li></ul></ul><ul><ul><li>Easy to produce derivatives for end-user distribution </li></ul></ul><ul><ul><li>Minimize costs of production, distribution & migration </li></ul></ul>
    9. 9. Sampling, Migration & Artifacts <ul><li>As in still image digitization, employing lossy compression can lead to artifacting when you migrate. </li></ul><ul><li>Unlike still images, lossy compression is assumed in almost all video processing technology today. </li></ul>
    10. 10. One River Media Codec Test Image Images courtesy of Marco Solorio, One River Media
    11. 11. Black Magic 8-Bit 4:2:2 Uncompressed Codec Images courtesy of Marco Solorio, One River Media
    12. 12. Black Magic 8-Bit: 10 th Generation Images courtesy of Marco Solorio, One River Media
    13. 13. One River Codec Test Images courtesy of Marco Solorio, One River Media
    14. 14. Digital Voodoo 10-bit Codec Images courtesy of Marco Solorio, One River Media
    15. 15. Digital Voodoo 10-bit: 10 th Gen. Images courtesy of Marco Solorio, One River Media
    16. 16. One River Codec Test Images courtesy of Marco Solorio, One River Media
    17. 17. Apple 4:4:4 “None”: 10 th Gen. Images courtesy of Marco Solorio, One River Media
    18. 18. Sampling, Migration & Artifacts <ul><li>4:4:4 sampling fulfills the digital promise of perfect copies across generations, but </li></ul><ul><li>Most video equipment doesn’t actually support it. Most high-end video editing packages on computers do and will store 4:4:4 to disk. </li></ul><ul><li>Lesson: if you want to store 4:4:4 uncompressed video, prepare to buy a lot of disk (or HSM), and abandon videotape. </li></ul>
    19. 19. Storing 4:4:4 Uncompressed Video <ul><li>QuickTime – Proprietary, but publicly documented and does the task, and software support is available </li></ul><ul><li>MJPEG 2000 – Open Standard (ISO/IEC 15444), supports 4:4:4 uncompressed. Software support iffy, but growing. </li></ul><ul><li>Material Exchange Format – Open Standard, but software support is weak, and some vendor issues </li></ul>
    20. 20. Storing 4:4:4 Uncompressed Video <ul><li>Videotape is a non-starter. D1 tape decks for uncompressed video cost $200K, and use 4:2:2. </li></ul><ul><li>Disk vs. HSM Tape </li></ul><ul><ul><li>Cost vs. Speed </li></ul></ul><ul><ul><li>Opportunities to detect bit rot, ability to migrate, time to produce derivatives </li></ul></ul><ul><li>Waiting on grid storage…. </li></ul>
    21. 21. Mind Games I: Conversion <ul><li>NYU has approximately 30,000 hours of moving image material, undigitized, in its special collections. Let’s digitize 1/10 of that. </li></ul><ul><li>9 Digitization/Editing workstations: $690,000 </li></ul><ul><li>9 conversion staff full time for 1 year: $350,000 </li></ul><ul><li>425 TB of Disk Storage @ $10k/TB = $4,250,000 </li></ul><ul><li>Grand Total: $5,290,000 </li></ul><ul><li>FYI, according to ARL, that’s nearly half our entire 2002 materials budget </li></ul>
    22. 22. Mind Games II: On-going costs <ul><li>Assume migration every 10 years. Assume time to migrate = 2x time of source material. </li></ul><ul><ul><li>6,000 hours x staff salary = ~$120K / 10 = $12k/year </li></ul></ul><ul><li>Assume new derivatives every 5 years, and time to migrate = 2x time of source material </li></ul><ul><ul><li>12,000 hours x staff salary = ~$240k / 10 = $24k/year </li></ul></ul><ul><li>3% disk loss/year x 425 TB = 12.75 TB replaced/year. Assuming disk prices are halved every two years, for next 10 years we’d have $38,750 total replacement costs, or $3,875/year. </li></ul><ul><li>Grand Total: ~$40K/year maintenance costs </li></ul>
    23. 23. Mind Games III <ul><li>On-going maintenance costs for 3,000 hours of video on disk aren’t particularly bad. </li></ul><ul><li>Initial conversion costs, however, are nightmarish. </li></ul><ul><li>If you don’t spend the money, however, your digital video is unlikely to prove any more preservation-worthy than analog. </li></ul>
    24. 24. NYU Costs: Capture Hardware Complete system cost: ~$125,000.00
    25. 25. NYU Costs: Conversion Personnel <ul><li>Currently conversion takes approximately 8 hours for every hour of tape. </li></ul><ul><li>Minimum personnel cost of ~$150/hour (staff time + benefits) for conversion </li></ul><ul><li>Hope to lower conversion time with practice (and better equipment), but at best, probably around $100/hour of tape. </li></ul>
    26. 26. NYU Costs: Repository Hardware <ul><li>Sun Enterprise 15K w/L700 Tape Backup: ~$400K/year </li></ul><ul><li>Sun T3 Disk Arrays (10 TB): ~$100K ($10K/TB) </li></ul>
    27. 27. NYU Costs: Repository Personnel <ul><li>Fractional part of NYU ITS Unix SysAdmin, Network Support Specialist, Tape Backup support, equivalent to about 1 FTE </li></ul><ul><li>~$75K/year </li></ul>
    28. 28. NYU Costs: Summary <ul><li>About $475K/year to keep our server alive and happy; $10K to add another terabyte </li></ul><ul><li>About $125K to add a new video capture/editing workstation </li></ul><ul><li>About $100-150 per hour of video to pay staff capture/conversion costs </li></ul>
    29. 29. The Good vs. the Perfect <ul><li>Good: 1 hour of video dubbed to Digital Betacam (w/duplicate master) and converted to DVD & MPEG4 streaming derivatives </li></ul><ul><ul><li>$150 staff time + $70 (2 digibeta tapes) + $3 (DVD-R blank w/case) + $24.75 (disk for MPEG4) = $247.75 </li></ul></ul><ul><li>Perfect: 1 hour of video converted to 4:4:4 uncompressed on disk (w/replicated backup) w/DVD & MPEG4 streaming derivatives </li></ul><ul><ul><li>$150 staff time + $2,860 (disk for master and backup) + $3 (DVD-R) + $24.75 (disk for MPEG4) = $3,037.75 </li></ul></ul>
    30. 30. Affordable Perfection <ul><li>Disk prices from 1992 to 2000 fell at about 45% per year. </li></ul><ul><li>If that holds, by 2010, the 1 TB which costs us $10,000 today will cost $276. </li></ul><ul><li>Storing 143 GB (one hour of 4:4:4 uncompressed video w/audio) will cost $39.50 ($4.50 more than a 60 minute Digital Betacam tape today). </li></ul>