Presentation (PowerPoint)

Report
19360 Business Center Drive
Northridge, CA 91324
www.ITSamerica.com
Transitioning from NTSC (analog)
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
SDI Digital Video
At the SDI source
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
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
October 26, 2011
Transitioning From NTSC to SDI Digital Video
Copyright ITS 2011
Sheet 5
Pixels
Many pixels
Many shades
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
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
October 26, 2011
Transitioning From NTSC to SDI Digital Video
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
Color Sample
Active Video SDI
Data Stream
Cr0-1
Y0
Color Sample
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
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 =(1125 x 2200/2) x 20 bits/pixel x 60 fields/sec
(60Hz field rate)
= 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
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
October 26, 2011
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
Display
Decompress
Compress
Buffer
xmit
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
Video Type
Example
Formats
Bit Rates
(Mbits/s)
Bit Rates
MJP2000
(Mbits/s)
@10:1
Bit Rates
MPEG-2
(Mbits/s)
@ 30:1
Bit Rates
MJP2000
(Mbits/s)
@40:1
Bit Rates
H.264
(Mbits/s)
@50:1
1 Stream
Video over
Ethernet
27
36
14
18
9
12
4.8
5.9
6.8
9
3.6
4.4
5.4
7.2
2.9
3.5
10 Base T
259M
SD-SDI
480i, 576i
270
360
143
177
344M
ED-SDI
480p, 576p
540
54
18
13.5
10.8
100Base T
292M
HD-SDI
720p,
1080i
1485
1470
148
147
49.5
37
29.7
100Base T
424M
3G-SDI
1080p
2970
2940
297
294
99
74
59.4
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
Analog Video
SDI Digital Video
Raw Video
Complex AM, FM and phase modulated Serial encoded bit stream at bit rates
signal requiring 6 MHz bandwidth
from 140 Mbits/s to 3000 Mbits/sec
Sync
Pedestal 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 Video
An 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/frame
Progressive and Interlaced
October 26, 2011
Many from 24.975 to 60 Hz and
beyond
Progressive and Interlaced
Transitioning From NTSC to SDI Digital Video
Copyright ITS 2011
26
Sheet 26
Comparing Analog to Digital Video
Attribute
Analog Video
SDI Digital Video
Visible Scan Lines
NTSC 480/frame
PAL 576/frame
480 SD
576 (PAL) SD
720 HD
1080 HD
Resolution/Line
This depends on the source and signal
quality but ranges to the equivalent of
300 to 720 pixels
SD 720 pixels
HD 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
27
October 26, 2011
Transitioning From NTSC to SDI Digital Video
Copyright ITS 2011
Sheet 27
SDTV
HDTV
Interlaced (I) Progressive (P)
Pixels & Bit Count, Data Rates, Resolutions & Specs
Active Luma
Active Total
Luma Samples Total
SMPTE
lines lines
Luma Aspect Frame Rate
Digitizing
Bit Rate
samples
in
SDI
Samples Ratio
Specification (MBit/Sec)
per
per
(Hz)
Bit Format
per Blanking (Pixels)
frame frame
Line
Area
SDTV
I
480
525
720 190
910
4:3
29.97
259M
ITU-R BT.601
143.18
HDTV
P
720
750
1280 370
1650
16:9
60 or
60/1.001
292M
ITU-R BT.709
1485.0
HDTV
(PAL)
P
720
750
1280 700
1980
16:9
50
292M
ITU-R BT.709
1485.0
HDTV
I
1080 1125
1920 280
2200
16:9
30 or
30/1.001
292M
ITU-R BT.709
1485.0
HDTV
(PAL)
I
1080
1125
1920 720
2640
16:9
25
292M
ITU-R BT.709
1485.0
HDTV
P
1080
1125
1920 280
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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