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Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 1 19360 Business Center Drive Northridge, CA 91324 www.ITSamerica.com October 26,

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Presentation on theme: "Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 1 19360 Business Center Drive Northridge, CA 91324 www.ITSamerica.com October 26,"— Presentation transcript:

1 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet Business Center Drive Northridge, CA October 26, 2011 Transitioning from NTSC (analog) to HD Digital Video

2 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 2 NTSC Analog Video October 26, 2011 NTSC video -color bar test pattern

3 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 3 SDI Digital Video October 26, 2011 At the SDI source At the end of a 100 meter cable

4 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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. October 26, 2011

5 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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) October 26, 2011 Few pixels Many shades Many pixels Few shades

6 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 6 Pixels October 26, 2011 Many pixels Many shades Specifying resolution Covers Pixel elements Shades of gray PER COLOR = number of colors

7 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 7 Pixel Depth; Color Depth; Colors October 26, bits = 4 colors 4 bits = 16 colors 8 bits = 256 colors 24 bits = 16 million colors Pictures from According to humans can distinguish up to 10 million colors According to humans can distinguish up to 10 million colors

8 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 October 26, 2011

9 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 9 Quick Idea About Subsampling 4:2:2 subsampling causes two luma samples to share one pair (Cr and Cb) of color samples October 26, 2011 Graphic from “Chrominance Subsampling in Digital Images”, by Douglas Kerr Cr 0-1 Y0Y0 Cb 0-1 Y1Y1 Cr 2-3 Y2Y2 Cb 2-3 Y3Y3 Sample Pair Pixel 0 Pixel 1Pixel 2Pixel 3 Color Sample Active Video SDI Data Stream

10 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 10 Pixels & Bit Count & Data Rate October 26, 2011 Key Points to Remember Each pixel = a Y (luma) sample Vertical blanking space adds lines; e.g. 45 in lines, plus blanking = 1125 lines/frame Horizontal blanking space adds samples; e.g. 280 Y samples per line in 1080/ visible pixels 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 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 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 11 Pixels & Bit Count & Data Rate October 26, 2011 BIT RATE= Resolution x sample depth x Fields/Frame X Frame Rate For 1080p/60= (1125 lines x 2200 pixels) x (20 bits/pixel) x 1 Field/Frame x 60 fps = (49,500,000 bits/image) x 1 x 60 fps =2,970,000,000 bits/second For 1080i/30 (60Hz field rate) =(1125 x 2200/2) x 20 bits/pixel x 60 fields/sec = 24,750,000/field x 60 = 1,485,000,000 bits/sec For 720p/60={(720+30) x ( )} x 20 bits/pixel x 30 fps x 2 =24,750,000/image x 60 = 1,485,000,000 bits/sec Calculating Bit Rates Bit rate examples assume 4:2:2 subsampling IAW SMPT 259M

12 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 12 Electronics October 26, 2011 Two 32 Bit RISC 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 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 1080pChoices Direct Connect (copper) SMPTE Specs SDI be capable of operating to 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 October 26, 2011

14 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 10.3 Gbit/sec up to Km Next level down “-LR” can support this rate up to 220 meters Radio Where would the band and bandwidth exist? October 26, 2011

15 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 October 26, 2011

16 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 16 The Compression Beast MPEG Coding Computationally Intensive More flexibility between image quality and frame rate tradeoff October 26, 2011

17 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 October 26, 2011

18 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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)  ms seconds to complete a 100 MB compression, 720p/1080i  74 ms to complete a buffer using :1 compression October 26, 2011 SDI SourceDecodeCompressxmit ReceiveBufferDecompressDisplay

19 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 19 Bit Rates October 26, 2011 SMPTEStandard Video Type Example Formats Bit Rates (Mbits/s) Bit Rates MPEG-2 30:1 Bit Rates H Stream Video over Ethernet 259MSD-SDI480i, 576i Base T 344MED-SDI480p, 576p Base T 292MHD-SDI 720p, 1080i Base T 424M3G-SDI1080p Base T

20 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 October 26, 2011

21 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 timeConclusion? 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 October 26, 2011

22 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 22 HD Video Spec Checklist October 26, 2011

23 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 October 26, 2011

24 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 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 October 26, 2011

25 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 25 Handy Reference Material October 26, 2011

26 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 26 Comparing Analog to Digital Video October 26,

27 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 27 Comparing Analog to Digital Video October 26,

28 Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 28 Pixels & Bit Count, Data Rates, Resolutions & Specs October 26, 2011


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