19360 Business Center Drive Northridge, CA 91324

Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 1

19360 Business Center DriveNorthridge, CA 91324www.ITSamerica.com

October 26, 2011

Transitioning from NTSC (analog)

to HD Digital Video


NTSC Analog Video

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NTSC video -color bar test pattern

http://upload.wikimedia.org/wikipedia/commons/8/83/Composite_Video.svg


SDI Digital Video

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At the SDI source

At the end of a 100 meter cable


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.

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Pixels

Pixels are a Multifaceted Picture Element Number of Pixels is Only a part

of the resolution story Shades of gray (steps, pixel

depth)

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Few pixelsMany shades

Many pixelsFew shades


Pixels

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Many pixelsMany shades

Specifying resolution Covers Pixel elements Shades of gray PER COLOR =

number of colors


Pixel Depth; Color Depth; Colors

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2 bits = 4 colors

4 bits = 16 colors

8 bits = 256 colors

24 bits = 16 million colors

Pictures from http://en.wikipedia.org/wiki/Color_depth

According to http://en.wikipedia.org/wiki/Color, humans can distinguish up to 10 million colors

http://en.wikipedia.org/wiki/Color

http://upload.wikimedia.org/wikipedia/commons/5/57/1_bit.png

http://en.wikipedia.org/wiki/File:8_bit.png

http://upload.wikimedia.org/wikipedia/commons/6/69/Truecolor.png


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

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Quick Idea About Subsampling

4:2:2 subsampling causes two luma samples to share one pair (Cr and Cb) of color samples

October 26, 2011Graphic from “Chrominance Subsampling in Digital Images”, by Douglas Kerr

Cr0-

1

Y0 Cb0-

1

Y1 Cr2-

3

Y2 Cb2-

3

Y3

Sample Pair Sample Pair Sample Pair Sample Pair

Pixel 0 Pixel 1 Pixel 2 Pixel 3

Color Sample

Color Sample

Active Video SDI Data Stream



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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)



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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 (1280+370) 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


Electronics

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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


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 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

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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?

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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

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MPEG Coding Computationally Intensive More flexibility between image quality and frame rate tradeoff

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MJPEG Coding Less computationally intensive due to the lack of prediction Less bit efficient, will force tradeoff between frame rate sooner,

image ringing

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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 compressionOctober 26, 2011

SDI Source Decode Compress xmit

ReceiveBufferDecompressDisplay


Bit Rates

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SMPTEStandard

Video Type

Example Formats

Bit Rates(Mbits/s)

Bit RatesMJP2000(Mbits/s)@10:1

Bit RatesMPEG-2(Mbits/s)@ 30:1

Bit RatesMJP2000(Mbits/s)@40:1

Bit RatesH.264

(Mbits/s)@50:1

1 Stream Video over

Ethernet

259M SD-SDI 480i, 576i

270 360 143177

27361418

9124.85.9

6.89

3.64.4

5.47.22.93.5

10 Base T

344M ED-SDI 480p, 576p 540 54 18 13.5 10.8 100Base

T

292M HD-SDI 720p, 1080i

14851470

148147 49.5 37 29.7 100Base

T

424M 3G-SDI 1080p 29702940

297294 99 74 59.4 1000

Base T



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

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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

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HD Video Spec Checklist

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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

playbackDesign 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

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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 precisionUse 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

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Handy Reference Material

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Comparing Analog to Digital Video

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26

Attribute Analog Video SDI Digital Video

Raw VideoComplex AM, FM and phase modulated signal requiring 6 MHz bandwidth

Serial encoded bit stream at bit rates from 140 Mbits/s to 3000 Mbits/sec

SyncPedestal and color burst sync areas scaled generally below the black level

A reserved bit pattern defined by SMPTE in the SDI stream

Blanking A predetermined voltage level in the video signal

Fixed format data blocks before and after the active video data set

Active VideoAn AM signal with overlaid phase modulated color information

A stream of video samples the number of which and format varies with resolution, sampling scheme and color depth

Frame/Field Rate

RS 170 60Hz /30 Hz Field/Frame RS170A (NTSC) 59.94 (60/1.001)CCIR 50Hz /25Hz field/frameProgressive and Interlaced

Many from 24.975 to 60 Hz and beyondProgressive and Interlaced


Comparing Analog to Digital Video

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27

Attribute Analog Video SDI Digital Video

Visible Scan Lines

NTSC 480/framePAL 576/frame

480 SD576 (PAL) SD720 HD1080 HD

Resolution/Line

This depends on the source and signal quality but ranges to the equivalent of 300 to 720 pixels

SD 720 pixelsHD 1280 and 1920 pixels

Color Sampling

Continuous time domain signal, intensity swings are limited by the available 1.5 MHz bandwidth

YUV encoding samples intensity every pixel and color differently depending on the encoding chosen. 4:2:2 is most frequently used


Pixels & Bit Count, Data Rates, Resolutions & Specs

SDTV HDTV

Interlaced (I)

Progressive (P)

Active lines per

frame

Total lines per

frame

Active Luma samples perLine

Luma Sample

s in Blanking Area

Total Luma

Samples

(Pixels)

Aspect

Ratio

Frame Rate (Hz)

SMPTE SDI Bit

Format

DigitizingSpecificati

on

Bit Rate (MBit/Sec

)

SDTV I 480 525 720 19

0 910 4:3 29.97 259M ITU-R BT.601 143.18

HDTV P 720 750 1280 370 1650 16:9

60 or60/1.00

1292M ITU-R

BT.709 1485.0

HDTV (PAL) P 720 750 1280 70

0 1980 16:9 50 292M ITU-R BT.709 1485.0

HDTV I 1080 1125 1920 28

0 2200 16:930 or

30/1.001

292M ITU-R BT.709 1485.0

HDTV (PAL) I 1080 112

5 1920 720 2640 16:9 25 292M ITU-R

BT.709 1485.0

HDTV P 1080 1125 1920 28

0 2200 16:9 60 424M ITU-R BT.709 2970.0

October 26, 2011

Documents

19360 Business Center Drive Northridge, CA 91324