19360 business center drive northridge, ca 91324
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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. - PowerPoint PPT PresentationTRANSCRIPT
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
Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 2
NTSC Analog Video
October 26, 2011
NTSC video -color bar test pattern
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
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
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 pixelsMany shades
Many pixelsFew shades
Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 6
Pixels
October 26, 2011
Many pixelsMany shades
Specifying resolution Covers Pixel elements Shades of gray PER COLOR =
number of colors
Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 7
Pixel Depth; Color Depth; Colors
October 26, 2011
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
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
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, 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
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 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)
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 (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
Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 12
Electronics
October 26, 2011
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 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 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 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?
October 26, 2011
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
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
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
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)
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
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 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
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
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 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 22
HD Video Spec Checklist
October 26, 2011
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
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
October 26, 2011
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 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
October 26, 2011
Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 25
Handy Reference Material
October 26, 2011
Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 26
Comparing Analog to Digital Video
October 26, 2011
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
Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 27
Comparing Analog to Digital Video
October 26, 2011
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
Transitioning From NTSC to SDI Digital Video Copyright ITS 2011 Sheet 28
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