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19360 Business Center Drive Northridge, CA 91324 www.ITSamerica.com

19360 Business Center Drive Northridge, CA 91324 www.ITSamerica.com. Transitioning from NTSC (analog) . to HD Digital Video. NTSC Analog Video. NTSC video -color bar test pattern. SDI Digital Video. At the SDI source. At the end of a 100 meter cable. Making stills move.

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19360 Business Center Drive Northridge, CA 91324 www.ITSamerica.com

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  1. 19360 Business Center DriveNorthridge, CA 91324www.ITSamerica.com Transitioning from NTSC (analog) to HD Digital Video

  2. NTSC Analog Video NTSC video -color bar test pattern

  3. SDI Digital Video At the SDI source At the end of a 100 meter cable

  4. Making stills move • There are two parts: • Frame Rate (pictures per second) • Set to give the illusion of smooth motion; beyond persistence of vision frequency. • Rates above 16 images/second yield smooth motion • 24 fps is used in film; 25 in the EC (PAL) and 30 in the USA (NTSC) • Illumination Rate (most often 2x frame rate) • Flicker fusion is the frequency that pulsing light looks steady • Illumination rate is pushed high enough to achieve flicker fusion • Film generally uses 48 Hz flicker rate, interlace TV scanning is 2x the frame rate.

  5. Pixels • Pixels are a Multifaceted Picture Element • Number of Pixels is Only a part of the resolution story • Shades of gray (steps, pixel depth) Few pixels Many shades Many pixels Few shades

  6. Pixels • Specifying resolution Covers • Pixel elements • Shades of gray PER COLOR = number of colors Many pixels Many shades

  7. Pixel Depth; Color Depth; Colors 2 bits = 4 colors 4 bits = 16 colors 8 bits = 256 colors 24 bits = 16 million colors According to http://en.wikipedia.org/wiki/Color, humans can distinguish up to 10 million colors Pictures from http://en.wikipedia.org/wiki/Color_depth

  8. Pixels & Bit Count & Data Rate • Why is this all of this important? BIT Rate; Some Basics • Bit rate pixel count X sampling & encoding method • Sampling: • The eye is more sensitive to intensity changes than color changes • Subsampling is delivering fewer color samples than luma samples for a group of pixels • 4:2:2 Subsampling = color at ½ luma rate • Image quality indistinguishable from sampling both at the same frequency • Sampling resolution is typically (TV) 10 bits per channel • Channels are Y (luma), Cr (red component), Cb (blue component) • Green derived from Y –Cr & -Cb (similar to analog video) • Sampling Frequency generally 74.xx MHz for HD

  9. Quick Idea About Subsampling • 4:2:2 subsampling causes two luma samples to share one pair (Cr and Cb) of color samples Color Sample Color Sample Active Video SDI Data Stream Graphic from “Chrominance Subsampling in Digital Images”, by Douglas Kerr

  10. Pixels & Bit Count & Data Rate • Key Points to Remember • Each pixel = a Y (luma) sample • Vertical blanking space adds lines; e.g. 45 in 1080 • 1080 lines, plus blanking = 1125 lines/frame • Horizontal blanking space adds samples; e.g. 280 Y samples per line in 1080/60 • 1920 visible pixels + 280 Y H blanking samples = 2200 pixels/line • Each pixel in 4:2:2 sampling is 20 bits deep • 10 bits of luma (Y) and 1 of the color components (Cr or Cb) @ 10 bits = 20 bits • Interlace Video delivers ½ the image in one field and the other half in a second field • Frame rate = ½ field rate (e.g. 1080i/30) • Progressive Video delivers a complete frame per scan • Frame rate = field rate (e.g. 1080p/60) • Frames may repeated at field rate (e.g. 1080p/30)

  11. Pixels & Bit Count & Data Rate Calculating Bit Rates Bit rate examples assume 4:2:2 subsampling IAW SMPT 259M

  12. Electronics Two 32 Bit RISC Processors @ 100 MHz Custom 43K CE FPGA to substitutes image samples, sample x sample in real time Custom 25K CE FPGA design to manage ITS substitution engine, specify text and graphic overlays, colors and housekeeping functions 3 GHz Data I/O Pathway with equalizers & drivers One 8 bit Z80 Microprocessor running at 4 MHz Custom 320 CE Gate Array to hold text bit maps and manage overlay timing 20 MHz Video amp and coax driver

  13. Transport • How do you get raw video (SDI) from source to destination? • Analog NTSC • any channel with a 6 MHz bandwidth will work • SD-SDI • Requires a channel capable of passing 143 MHz data rate • HD-SDI • Requires 1.5 GHz channel for 720p/1080i and 3 GHz for 1080p • Choices • Direct Connect (copper) • SMPTE Specs SDI be capable of operating to 100-200 meters of 75 Ω Coax (e.g Belden 1694A) • These do require line equalizers and drivers; Reclocking is generally needed to properly decode • Short runs can use Cat 6A/Cat 7 copper cable for short runs (10 m); CAT 5 and standard CAT 6 will not work

  14. Transport • Choices (cont.) • Ethernet • At 1G Ethernet, ED-SDI can work • At 1 G Ethernet, 720p/1080i will not work • 10G Fiber Only full duplex only • 100G Fiber Only, full duplex, still evolving • Fiber • 10GBASE-ER single-mode fiber supports transport @ 10.3 Gbit/sec up to 30-40 Km • Next level down “-LR” can support this rate up to 220 meters • Radio • Where would the band and bandwidth exist?

  15. The Compression Beast • Compression is a tool to reduce data rate • Alternative to whole new infrastructures • Typical Compression Ratios that maintain excellent image quality • H.263 and MPEG-2 ; 30:1 • MJPG 2000; 20:1 to 40:1 • H.264/MEG-4 part 10; 50:1 • Compression Issues • Interframe prediction (MPEG) vs. image compression (M-JPG) • MPEG is motion sensitive • M-JPG can generate “rings” at the harsh image edges • Trade off between image quality and frame rate/Frame dropping • Latency

  16. The Compression Beast • MPEG Coding • Computationally Intensive • More flexibility between image quality and frame rate tradeoff

  17. The Compression Beast • MJPEG Coding • Less computationally intensive due to the lack of prediction • Less bit efficient, will force tradeoff between frame rate sooner, image ringing

  18. The Compression Beast • Latency∑ decode (sdi-image stream) + compression + xmit latency + buffer time + decompress + decode for display • Compression • Many factors including image content, motion between frames, hardware speed • Buffer Time • Decompression requires a complete data set and enough buffered data to ensure every frame is reconstructed at the full expected frame rate • 4-5 frames of data may be needed up to 20 depending compression parameters (MPEG) • 83-300 ms seconds to complete a buffer @t 100 MB Ethernet @30:1 compression, 720p/1080i • 74 ms to complete a buffer using MJPEG2000 @ 2-3 frames; @ 20:1 compression SDI Source Decode Compress xmit Display Decompress Buffer Receive

  19. Bit Rates

  20. The Compression Beast • Accuracy of time stamps at the destination (the method used in analog NTSC) is unpredictable do to wide variation in latency • Transport mechanism • Encoding/Decoding mechanism • Amount of pre-image regen buffering • Camera control more difficult due to image latency • Conclusion? • Time stamping must be at the source of the SDI digital video stream • Transport necessities will not impact time stamping accuracy • Manage transport bandwidth to minimize latency

  21. The Compression Beast • Degraded Image Quality Threat • Degree of compression needed • Video content • Hardware CODEC speeds • Transport bandwidth • Degraded image quality issues • Fine detail may be smeared or lost to macroblocks • Overlay text may be smeared or unreadable • Size of characters chosen for time stamping and other critical data at record time may not be appropriate displays at analysis and playback time • Conclusion? • Time stamp and store critical information in SDI metadata stream at the source • Ancillary Packet Format (metadata) per SMPTE 291M and related specifications • Survives compression losslessly • Decoder can overlay at display time • Parameters of overlay can be adjusted to suit the display

  22. HD Video Spec Checklist

  23. HD Video Spec Checklist • Use SDI video sources • Must be SMPTE compliant • Digital equivalent of the raw video • Must preserve meta data • Use recording devices that preserve metadata • Metadata decoders can then place critical data on the video at playback • Design your system such that • Specify a system that stamps at a finite instance in the video (e.g. vertical sync) • Time stamps and other time to image critical data is impressed into the SDI video stream and meta data at the source • Eliminates any latency sources • Genlock your video sources

  24. HD Video Spec Checklist • Avoid systems using standard SMPTE time stamp encoding • SMPTE standard is accurate to the second, but only records frame number thereafter • Use equipment that time stamps at a finite point in the SDI stream (e.g. vertical sync) • Use equipment that captures time in fractions of a second • e.g. 6980G-HD captures to 100 µS precision • Use Equipment with interoperable metadata encoding • STANAG 4609 is a possible method • Is in use in several NATO and US programs • Provides a non-proprietary format for encoding accurate time and other critical data • Builds on and compliant with SMPTE 291M and related specifications

  25. Handy Reference Material

  26. Comparing Analog to Digital Video

  27. Comparing Analog to Digital Video

  28. Pixels & Bit Count, Data Rates, Resolutions & Specs

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