High-Definition Television Basics

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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19 feb 2006

High-Definition Television Basics Signal structures, data rates, and physical interface characteristics of HDTV signals

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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.

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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.

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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.

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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

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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

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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

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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

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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

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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

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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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HD Signal Structure Line Numbering Details

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HD Signal Structure CRC Details CRC polynomial: CRC(X) = X18 + X5 + X4 + 1

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HD Signal Structure Multiplexing Y and Cb/Cr streams

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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

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Signal timing 1920 x 1080

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Signal timing 1280 x 720

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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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HD Signal Structure Image sample structure & frame rates for 1280 x 720 systems

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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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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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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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HD Ancillary Data Ancillary data is carried in the video data and not crucial to recovering the video image.

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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).

•

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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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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

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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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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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Effects of Limited Bandwidth on High Definition Signals Data Rates and physical layer issues

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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.

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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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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!

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HD Physical Interface

•

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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)

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19 feb 2006

HD Physical Interface

•

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Similar to Transmission line Tests –

Return Loss

–

VSWR

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19 feb 2006

Testing the HD Physical Interface

The data recovery process begins with the extraction of the clock signal from the video data.

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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.

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The recovered clock is used to recover the video data, noise added to this process will also hinder the data’s stability.

•

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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

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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

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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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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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Questions?

TVM Series

VTM Series

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19 feb 2006