HD Basics
Jochen Kuhnen Market Development Manager T&M Tel. +49 8093 904082 Fax +49 8093 904083 e-mail jochen.kuhnen@leitch.com
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assuredcommunications™
19 feb 2006
High-Definition Television Basics Signal structures, data rates, and physical interface characteristics of HDTV signals
#2
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19 feb 2006
Overview • What is “High Definition”? – High Definition Television (HDTV) describes a signal format that has considerably more information in each picture than does standard definition (SD). This includes both more samples per video line (or a higher bandwidth for analog HD) as well as more lines in each video field or frame.
#3
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19 feb 2006
Overview • High Definition Formats – There are two main HD video formats currently in use, one with 720 active video lines and the other with 1080. The 720 line format has 1280 luma samples per active line while the 1080 line format has 1920. These formats are sometimes described as 1280 x 720 and 1920 x 1080. All of the 1280 x 720 formats are progressive, but some of the 1920 x 1080 formats are interlaced. Frame rates ranging form 23.98 Hz to 60 Hz.
#4
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19 feb 2006
Overview • HD is built on SD – Differences and similarities between SD and HD formats will be described later, but HD is built on many of the same principles as is SD. An understanding of SD video aids in learning HD.
#5
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19 feb 2006
Pertinent HDTV Standards • SMPTE 274M-2005 - 1920x1080 Image Sample Structure, Digital Representation and Digital Timing Reference Sequences for Multiple Picture Rates
• SMPTE 296M-2001 - 1280 x 720 Progressive Image Sample Structure — Analog and Digital Representation and Analog Interface
• SMPTE 291M-1998 - Ancillary Data Packet and Space Formatting
• SMPTE 292M - Bit-Serial Digital Interface for HighDefinition Television Systems
• ITU-R BT.709-4 -Parameter Values for the HDTV Standards for Production and International Programme Exchange #6
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19 feb 2006
HD vs. SD • Similarities – – – –
10 bits per data word Y Cb Cr native format Blanking area is defined to carry ancillary data Embedded audio can carry 16 mono channels in ancillary space – A CRC-based scheme to validate data transmissions
#7
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19 feb 2006
HD vs. SD • Differences – Color space- Y Cb Cr derivations from RGB use different coefficients – Data rate- 270 Mb/s SD; 1.485 Gb/s HD – HD is conceptually two separate data streams- one for Y, the other for Cb/Cr – Formats- only two for SD (625/50 and 525/59.94); HD has many different frame rates defined, with a mix of progressive, interlaced, and segmented frame formats – Aspect ratio- HD is 16 x 9
#8
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19 feb 2006
HD vs. SD • Differences (cont.) – HD uses a CRC per each line of each stream (Y and Cb/Cr); SD used a single CRC per field – HD embeds the line number in each line – HD more thoroughly specifies embedded audio distribution
#9
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19 feb 2006
HD Color Space • HD color space definition, from ITU-R BT.709: Y = 0.715G + 0.072B + 0.213R Cb = -0.715G + 0.928B - 0.213R Cr = -0.715G - 0.072B + 0.787R
• SD color space definition, from ITU-R BT.601: Y = 0.587G + 0.114B + 0.299R Cb = -0.587G + 0.886B -0.299R Cr = -0.587G - 0.114B + 0.701R
#10
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19 feb 2006
HD Color Space Effect of colorimetry on waveforms
RGB representation of the color bar waveforms are identical
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19 feb 2006
HD Color Space Effect of colorimetry on waveforms
Note the obvious difference in Y component, due primarily to the larger proportion of the green primary in the HD encoding of luminance
#12
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19 feb 2006
HD Data Rates • Serial transmission of HD is at either 1.485 Gb /s or 1.4835 Gb/s (1.485/1.001) • Derivation of these rates: – Luma sampling frequency is 74.25 Ms/s or 74.176 Ms/s – Cb and Cr are sampled at half these rates but then combined into a single 74.25 Ms/s stream. – Since each data word contains 10 bits the resulting bit rate is (74.25Msample/s x 2) x 10 bits/sample= 1.485 Gb/s
#13
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19 feb 2006
HD Signal Structure • Y Cb Cr native format components – Derived from gamma-corrected RGB components per ITU-R BT.709
• 4:2:2 Sampling Structure – Refers to the luma sample rate being twice that of both Cb and Cr. – Active portion of a video line always starts with a Cb sample
• Active lines & luma samples – Only two combinations for active video- 1920 x 1080 and 1280 x 720 – But total number of luma samples can change considerably based on frame rate #14
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19 feb 2006
HD Signal Structure Line-rate Video Word Distribution
Note: Not to Scale
Line N
EAV +LN +CRC 8 Samples
Video Blanking Space Blanking values or ancillary data
SAV 4 Samples
Line N+1
Active Video Space 1920 or 1280 luma samples
EAV 4 Samples
Number of sample varies with standard and field rate
EAV- “End of Active Video”. Four-word code representing the start of blanking SAV- “Start of Active Video”. Four-word code representing the end of blanking Video Blanking- As in analog standards the portion of the video signal not displayed when the image is viewed. Used for ancillary data, particularly embedded audio. The number of blanking samples varies from 280 to 2845. Active Video - Those samples actually viewed. Each viewable sample has a Y, Cb, and Cr component. Either 1920 or 1280 luma samples. Luma Sample = One 74.25 MHz (or 74.25/1.001 MHz) clock period #15
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19 feb 2006
HD Signal Structure EAV and SAV Structure Word 0 1 2 3
Hex Value 3FF 0 0 variable
9 1 0 0 1
8 1 0 0 F
7 1 0 0 V
6 1 0 0 H
Bit Number 5 4 3 1 1 1 0 0 0 0 0 0 P3
P2
P1
2 1 0 0 P0
1 1 0 0 0
0 1 0 0 0
F = Field bit; F=0 for field 1 and F=1 for field 2 (Note: progressive scan systems always have F=0) V = Vertical blanking; V=1 when in vertical blanking H = EAV/SAV; H=1 for EAV; H=0 for SAV
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19 feb 2006
HD Signal Structure Line Numbering Details
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19 feb 2006
HD Signal Structure CRC Details CRC polynomial: CRC(X) = X18 + X5 + X4 + 1
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19 feb 2006
HD Signal Structure Multiplexing Y and Cb/Cr streams
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19 feb 2006
HD Signal Structure Multiplexing Y and Cb/Cr streams •EAV, LN, and CRC begin blanking •Cb is always the first active word
Line N
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Line N+1
19 feb 2006
Signal timing 1920 x 1080
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19 feb 2006
Signal timing 1280 x 720
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19 feb 2006
HD Signal Structure • 1920 x 1080 line numbering:
Blanking 1 Active Video 1 Blanking 1
p-Systems
i/sF Systems
1 to 41
1 to 20
42 to 1121
21 to 560
1122 to 1125
561 to 563
Blanking 2
564 to 583
Active Video 2
584 to 1123
Blanking 2
1124 to 1125
• Sync duration is 5 lines, rest is for ancillary data • Field duration in i/sF systems is 562.5 lines
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19 feb 2006
HD Signal Structure • 1280 x 720 line numbering: – Blanking: 1 to 25 – Active Video: 26 to 745 – Blanking: 746 to 750
• Sync duration is 5 lines, rest is for ancillary data
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19 feb 2006
HD Signal Structure Image sample structure & frame rates for 1920 x 1080 systems
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19 feb 2006
HD Signal Structure Image sample structure & frame rates for 1280 x 720 systems
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19 feb 2006
HD Signal Structure Blanking length variations in 1280 x 720 systems
Note that for this subset of the 1280 x 720 formats the ratio of blanking to active samples increases substantially- up to greater than 2:1 for 30Hz frame rate!
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19 feb 2006
Segmented Frame Standards • Only for 1920 x 1080 systems, e.g. 1080psF/25: – Progressive scan at 25Hz in the camera – Interlaced transmission and display at 50Hz
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19 feb 2006
EBU Recommendation • Code of practice to describe HD formats – Number of active lines – Scanning scheme – Frame rate (not field rate!)
• 1080i/50 does not exist, becomes 1080i/25!!!
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SMPTE
EBU
1080/50/i
1080i/25
720/50/p
720p/50
1080/50/p
1080p/50
1080/25/p(sF)
1080p(sF)/25
1080/24/p(sF)
1080p(sF)/24
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19 feb 2006
HD Signal Structure • Active picture information • 720p/50 – 1280 x 720 x 50 = 46Mpixel/s
• 1080i/25 and 1080psF/25 – 1920 x 1080 x 25 = 52Mpixel/s
• 1080p/50 – 1920 x 1080 x 50 = 104Mpixel/s
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19 feb 2006
HD Ancillary Data Ancillary data is carried in the video data and not crucial to recovering the video image. •
Ancillary data may be completely unrelated to the image and may include, but are not limited to: •
Embedded AES/EBU Audio Dolby Encoded Audio Closed Captions (Rec. 709) Teletext Sub-titles Copy Protection bit
Wide Screen Signaling XDS Information AMOL Information VITS Proprietary Data Other TBD!
Ancillary data packets are preceded with the number 000h (all zeros) followed by two occurrences of 3FFh (all ones) then followed by a DID (unique data identification word). •
#31
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19 feb 2006
HD Ancillary Data Ancillary Packet Details •Ancillary data header is 000h 3FFh 3FFh- the opposite of the 3FF 000 000 sequence of EAV/SAV
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19 feb 2006
HD Ancillary Data Some common DID values-
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Ancillary data type
DID value
Video Payload Identifier SMPTE RP-188 Time Code Closed Captioning Program Description AES Audio Group 1 HD Embedded Audio Group 1 Group 2 Group 3 Group 4
241 260 161 162 2FF 2E7 1E6 1E5 2E4
assuredcommunications™
19 feb 2006
Extensions to the HD Specifications • Dual Link (SMPTE 372M) – SMPTE 372M defines a system using two physical transmission links to carry a single video source at higher color difference sampling frequency, bit depth, or some combination of both. – RGB and RGB +A formats are also defined
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19 feb 2006
Extensions to the HD Specifications Dual Link Formats
Note: Dual link is currently the only way to realize the 1920 x 1080 50Hz, 59.94Hz, and 60Hz frame rate progressive systems
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19 feb 2006
Extensions to the HD Specifications Dual Link Formats- Example of distributing components in a RGB +A 4:4:4:4 system
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19 feb 2006
Effects of Limited Bandwidth on High Definition Signals Data Rates and physical layer issues
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19 feb 2006
HD Physical Layer Characteristics
• • • • •
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Amplitude- 800 mV p-p +/- 10% 1.485 (or 1.465/1.001) Gb/s Jitter should be <70 ps (!) Ringing & Overshoots <10% Some of these specs will only be met directly out of a generator!
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19 feb 2006
HD Physical Interface
VTR / Server Codec / Encoder
HD Interface < 100 m when using copper coaxial cables.
#39
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19 feb 2006
HD Physical Interface
Data Rate 2
= Frequency
For High definition Serial Digital Video, the data rates are 1.485 Gb/s and 1.4835 Gb/s (29.97 & 59.94 Vertical Rates), or:
1.485 Gb/s = 742.5 MHz 2
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1.4835 Gb/s =741.7 MHz 2
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19 feb 2006
HD Physical Interface
Fundamental and 3rd Odd
Result of Fundamental + 3rd Odd
Fundamental, 3rd and 5th Odd #41
Result of Fundamental, 3rd and 5th Odd
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19 feb 2006
HD Physical Interface
•
Analog Composite Signal Characteristics: – – – –
•
Digital Signal Characteristics : – – – –
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Highest Frequency 6 (NTSC) or 8 MHz (PAL) 1 V p/p Coaxial Cable Working distance (approx.) 333 m. Composite analog signal
Highest Frequency 742.5 MHz 800 mV Coaxial Cable Working distance (approx.) 80 -100 m. Square wave - 5th Odd harmonic 2.2275 GHz !
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19 feb 2006
HD Physical Interface
Ultra-High Frequency (UHF Band): 300 MHz to 3000 MHz UHF TV Channels up to around 800 MHz
HD Square wave - 5th Odd harmonic 2.2275 GHz! RF = Rocket Science!
#43
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19 feb 2006
HD Physical Interface
•
•
Analog Transmission Line Losses include: –
High Frequency Image Content
–
Video Phase Changes (2O per foot)
–
Reflections (image ghosts)
Digital Transmission Line Losses : – High Frequency Carrier –
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Reflections (standing waves / data)
assuredcommunications™
19 feb 2006
HD Physical Interface
•
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Similar to Transmission line Tests –
Return Loss
–
VSWR
assuredcommunications™
19 feb 2006
Testing the HD Physical Interface
The data recovery process begins with the extraction of the clock signal from the video data. •
Noise added to the signal during equalization will accompany the recovered clock. The greater the amount of noise, the less precise the recovery of the clock resulting in clock jitter. •
The recovered clock is used to recover the video data, noise added to this process will also hinder the data’s stability. •
#46
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19 feb 2006
Testing the HD Physical Interface
RGB UPPER = 710 mV LOWER = -10mV
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This image represents a typical eye pattern from a HD signal connected with less than 10 m of cable.
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19 feb 2006
Testing the HD Physical Interface
RGB UPPER = 710 mV LOWER = -10mV
#48
This image represents the eye pattern of a HD signal, note the absence of odd harmonics, less than 20m of connecting cable.
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19 feb 2006
Testing the HD Physical Interface
RGB UPPER = 710 mV LOWER = -10mV
#49
This image represents the eye pattern of a HD signal, loss in stability of the eye with 80 m of cable. The â&#x20AC;&#x2DC;eye is closing due to a large amount of jitter.
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19 feb 2006
Testing the HD Physical Interface
This image demonstrates the eye pattern of a HD signal barely open. The signal is very near the digital cliff. However, the monitoring device recovers enough information to decode the video.
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19 feb 2006
Testing the HD Physical Interface
RGB UPPER = 710 mV LOWE R= -10mV
RGB UPPER = 710 mV LOWE R= -10mV
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This image demonstrates a 50% loss in signal due to the transmission line.
This image is the result of adding persistence to the same eye pattern display. A much better look at jitter can be presented over time.
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19 feb 2006
Summary
Testing the performance of high definition video has its roots in high frequency analog signal analysis, data analysis, and video conformance. All engineers working with uncompressed high definition video require an awareness of 'multiple discipline' test methods. The Eye Pattern display represents a method to quantify the sum of the effects degrading the physical characteristics of an HD SDI signal.
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19 feb 2006
Questions?
TVM Series
VTM Series
#53
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19 feb 2006