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Transitioning from NTSC (analog)

19360 Business Center Drive

Northridge, CA 91324 www.ITSamerica.com

to HD Digital Video

October 26, 2011 Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 1

NTSC Analog Video

NTSC video -color bar test pattern

October 26, 2011 Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 2

At the SDI source

SDI Digital Video

At the end of a 100 meter cable

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 3

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

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 4

Pixels are a Multifaceted Picture Element

 Number of Pixels is Only a part of the resolution story

 Shades of gray (steps, pixel depth)

Pixels

Few pixels

Many shades

October 26, 2011

Many pixels

Few shades

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 5

Many pixels

Many shades

Pixels

Specifying resolution Covers

 Pixel elements

 Shades of gray PER COLOR = number of colors

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 6

Pixel Depth; Color Depth; Colors

2 bits = 4 colors

4 bits = 16 colors

8 bits = 256 colors

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

24 bits = 16 million colors

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

Transitioning From NTSC to SDI Digital Video

October 26, 2011

Copyright ITS 2011

Sheet 7

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

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 8

Quick Idea About Subsampling

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

Active Video SDI

Data Stream

Cr

0-1

Color Sample

Y

0

Sample Pair

Cb

0-1

Y

1

Sample Pair

Pixel 0 Pixel 1

Cr

2-3

Color Sample

Y

2

Sample Pair

Pixel 2

Cb

2-3

Pixel 3

Y

3

Sample Pair

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

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 9

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)

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 10

Pixels & Bit Count & Data Rate

Calculating Bit Rates

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

Bit rate examples assume 4:2:2 subsampling IAW SMPT 259M

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 11

October 26, 2011

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

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 12

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

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 13

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?

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 14

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

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 15

The Compression Beast

MPEG Coding

 Computationally Intensive

 More flexibility between image quality and frame rate tradeoff

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 16

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

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 17

The Compression Beast

Latency

∑ decode (sdi-image stream) + compression + xmit latency + buffer time + decompress

+ decode for display

SDI Source Decode Compress xmit

Display Decompress Buffer Receive

 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

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 18

Bit Rates

SMPTE

Standard

259M

344M

292M

424M

Video Type

SD-SDI

ED-SDI

HD-SDI

3G-SDI

Example

Formats

480i, 576i

480p, 576p

720p,

1080i

1080p

Bit Rates

(Mbits/s)

270

360

143

177

540

1485

1470

2970

2940

Bit Rates

MJP2000

(Mbits/s)

@10:1

27

36

14

18

54

148

147

297

294

Bit Rates

MPEG-2

(Mbits/s)

@ 30:1

9

12

4.8

5.9

18

49.5

99

Bit Rates

MJP2000

(Mbits/s)

@40:1

6.8

9

3.6

4.4

13.5

37

74

Bit Rates

H.264

(Mbits/s)

@50:1

5.4

7.2

2.9

3.5

10.8

29.7

59.4

1 Stream

Video over

Ethernet

10 Base T

100Base T

100Base T

1000 Base T

October 26, 2011 Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 19

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

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 20

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

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 21

HD Video Spec Checklist

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 22

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

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 23

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

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 24

Handy Reference Material

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 25

Comparing Analog to Digital Video

Attribute

Raw Video

Sync

Blanking

Active Video

Frame/Field Rate

October 26, 2011

Analog Video SDI Digital Video

Complex 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

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

A predetermined voltage level in the video signal

An AM signal with overlaid phase modulated color information

RS 170 60Hz /30 Hz Field/Frame

RS170A (NTSC) 59.94 (60/1.001)

CCIR 50Hz /25Hz field/frame

Progressive and Interlaced

A reserved bit pattern defined by

SMPTE in the SDI stream

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

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

26

Many from 24.975 to 60 Hz and beyond

Progressive and Interlaced

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 26

Comparing Analog to Digital Video

Attribute

Visible Scan Lines

Resolution/Line

Color Sampling

Analog Video

NTSC 480/frame

PAL 576/frame

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

300 to 720 pixels

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

SDI Digital Video

480 SD

576 (PAL) SD

720 HD

1080 HD

SD 720 pixels

HD 1280 and 1920 pixels

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

27

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 27

Pixels & Bit Count, Data Rates, Resolutions & Specs

SDTV

HDTV

Active lines per frame

Total lines per frame

Active

Luma samples per

Line

Luma

Samples in

Blanking

Area

Total

Luma

Samples

(Pixels)

Aspect Frame Rate

Ratio (Hz)

SMPTE

SDI

Bit Format

Digitizing

Specification

Bit Rate

(MBit/Sec)

SDTV I

HDTV

HDTV

(PAL)

HDTV

P

P

I

HDTV

(PAL)

I

HDTV P

480 525 720 190

720 750 1280 370

720 750 1280 700

1080 1125 1920 280

1080 1125 1920 720

1080 1125 1920 280

910 4:3 29.97

1650 16:9

60 or

60/1.001

1980 16:9 50

2200 16:9

30 or

30/1.001

2640 16:9 25

259M ITU-R BT.601

143.18

292M ITU-R BT.709

1485.0

292M ITU-R BT.709

1485.0

292M ITU-R BT.709

1485.0

292M ITU-R BT.709

1485.0

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

2970.0

October 26, 2011

Transitioning From NTSC to SDI Digital Video

Copyright ITS 2011

Sheet 28

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