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UNDERSTANDING HDTV TECHNOLOGY

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Title: UNDERSTANDING HDTV TECHNOLOGY


1
UNDERSTANDING HDTV TECHNOLOGY
  • By Peter Wilson, HDDC

2
The Seminar
  • Brief History of HDTV
  • Whats your definition of high definition?
  • Moving image portrayal
  • Compression of HDTV
  • Practical Issues
  • Cameras
  • HD recorders
  • Displays

3
HD History
4
Milestones
  • 1984 RAI Arlecchino
  • 1985 RAI Oniricon
  • 1985 CCIR vote lost in Dubrovnic
  • 1986 European HD Project started
  • 1987 Film out with Electron Beam Recorder
  • 1988 Genesis at Wembly , Montreux Jazz
  • 1988 Digital Cinema in Brighton
  • 1988Eureka in Brighton
  • 1992 Winter Olympics
  • 1998 ATSC
  • 2001-2003 Early Adopters
  • 2008 HD Services

5
Your definition of HDTV
  • High-definition television (or HDTV) is a
    digital television broadcasting system with
    higher resolution than traditional television
    systems (standard-definition TV, or SDTV). HDTV
    is digitally broadcast the earliest
    implementations used analog broadcasting, but
    today digital television (DTV) signals are used,
    requiring less bandwidth due to digital video
    compression.
  • Wikipedia

6
NHK fundamental research
HDTV
NTSC
12
480 lines
16
1080 lines
9
11º
9
28 º
Distance is 7 screen heights
Distance is 3 screen heights
Ideal viewing distance in picture heights is
about 3400 divided by the number of picture lines
For the 480 lines of 525-line TV, the ideal
viewing distance is 7 times screen height, and
the horizontal viewing angle 11º
For the 1080 lines of typical HDTV, the ideal
viewing distance is 3.2 times screen height and
the horizontal viewing angle 28º
7
Technical Issues
  • Progressive V Interlace
  • Compression is the root of all evil
  • Sensor size and technology
  • Processing speed and storage capacity
  • Subsampling 444,422, 420, 311
  • Interfacing
  • Long GOP editing on HDV
  • Come back Mole all is Forgiven

8
Format Types
HDTV comes in three different formats depending
upon how the image has been scanned and
distributed- 1. Interlaced 2. Progressive 3.
Segmented frame
9
Interlaced Progressive
Interlace Scan
Progressive Scan
Field 1
Field 2
10
Why bother with Interlace?
It gives us a 21 bandwidth reduction This allows
to have a system with greater spatial resolution
Whats the cost?
Potential for artifacts (twitter and
alias) Difficulty in processing Compression
efficiency is potentially lower
11
Segmented Frame Format
Field 1
Distribute as 2 Interlaced Fields
Scan as 1 Progressive Frame
Field 2
12
Segmented Frame Judder
If SF is viewed on a monitor, moving objects
judder-
Smooth motion expected by brain
Vertical Position
SF behind smooth profile
SF ahead of smooth profile
Motion profile of SF
Time
13
HDTV Format Names
Standards are generally known by a name made from
the number of active lines, plus the format, plus
the field/frame rate
e.g. 19201080/29.97/21 1080i/29
21 interlace 11 progressive
sF segmented frame (sometimes psf)
Frame rate OR sometimes field rate for i formats
Number of active pixels in a line
Number of active lines in a frame
14
The 1080 Family 274M
1920
Total lines per frame 1125 Active lines per frame
1080 Active pixels per line 1920
1125
1080
Variable
Pixels are square. (1080 16/9 1920) Total
pixels per line varies with frame rate (e.g 2200
for 59.94i, 2640 for 50i)
1080P 24 popular for product finished on
film 1080i popular for programmes shot for TV
release and for sports events
15
The 720p Family 296M
1280
Lines per frame 750 Active lines per frame
720 Active pixels per line 1280 Always Progressive
750
720
Variable
Total number of pixels per line varies with frame
rate (e.g 1650 for 60, 4125 for 24) Pixels are
square. (720 16/9 1280)
16
ITU-R BT709/274M
Recommendation BT.709 (ITU-R BT.709-5) defines an
international digital HDTV production standard
based on a high definition "Common Image Format"
(HD-CIF) structure of 1920x1080, 169 (square
pixel) aspect ratio.
This standard can be applied in any environment,
50 Hz in Europe, 60 Hz in United States and
Japan, and 24 Hz in the film industry.
Common Image Format will help to speed up the
introduction of HDTV throughout the world Allow
producers in every country to address global
markets for their content. Even producers who
live in countries that still have no plans for
offering HDTV programmes can produce their
content in HDTV, so that it can be shown in HDTV
format in those countries that have already
introduced HDTV services.
17
HDTV Interfacing
  • Component formats only
  • (No composite formats)
  • 169 aspect ratio
  • (no 43)
  • Tri-level analog sync
  • (Not bi-level)
  • New colorimetry
  • (New bars patterns etc)

18
Colourimetry Compared to SD
Large change to the equations for calculating
Y,Pb,Pr from R,G,B Gamma set at 0.45 (maximum
slope 4.5) Displaying HDTV pictures on non-HDTV
monitors can give haphazard results Conversion
equipment may need to change the colour space to
be correct
19
The Digital Serial Interface (HDSDI)
Derived from the standard def SDI system Carries
luma sampled at 74.25MHz Carries 2 chroma
channels sampled at 37.125MHz Uses a single
1.485 Giga-bit per second link Can use coaxial
cable or optical link
20
Audio
HDSDI can carry 2 to 16 audio channels organized
as 1 to 8 channel pairs Synchronous 48kHz audio
sampling is preferred but it can support
synchronous or asynchronous rates from 32 to
48kHz 24 bit audio is carried Effectively embeds
AES/EBU style audio packets
21
Dual Link 372M
Dual 1.485Gbit/s 292M interface High frame rate
progressive 422 YCbCr Interlaced 4444
12-bit formats Alpha channel
22
3Gbps Single link 425M
  • Single 3G Link Can Carry
  • 1080P25 RGB
  • 1080P50 Y Pb Pr
  • 2x 1080P25 Y Pb Pr (Level B is simple duplex)
  • 2 Modes Level A B
  • 3 Formats
  • Up to 100 Metres with gooddesign

23
Compression
  • Compression is not desirable but necessary
  • Compression is a system for data rate reduction
  • Compression can be lossless or lossy
  • Compression is used to facilitate data transfer
    and storage when there is not enough bandwidth
    availiable
  • Compression can be optimised for quality or
    efficiency
  • Studio Compression is normally quality
  • Transmission is normally efficiency

24
Compression How it works
  • The picture is analysed by a mathematical
    transform, Wavelet or Discreet Cosine Transform
    (DCT)
  • The resultant analysis is Quantised (Data values
    reduced) (Quantel Quantised Television)
  • The result is entropy encoded
  • This results in a basic compression with low
    efficiency but possibly high quality

25
Compression How it Works 2
  • To improve the efficiency the compression can be
    spread over time
  • At the start an I (Intra) frame is generated
  • I Frame only compression only uses Intra Frames
  • Next come predicted frames which are
    synthetically generated
  • Following this are Bidirectional frames by
    playing tricks with time.
  • For Editing I is best followed by I-P, avoid I-P-B

26
Compression issues
  • Wavelets are good for high resolution, JPEG2000,
    VC2
  • DCT with Block motion estimation are not so good
    for high resolution.
  • Codecs with Block motion estimation fail with
    blocks
  • It is bad to concatenate dissimilar codecs
  • It is bad to edit IBP, best I frame only

27
Compression formats
28
Chroma Subsampling
29
Cameras Production Values
  • Small Format Cameras
  • Concatenation of dissimilar Compression
  • Light it in Post
  • Where did all the black detail go?
  • Depth of field
  • Lens Quality
  • Shooting for Large Screens

30
What is a K?
The Binary representation of 1000 (1024) A poor
Metric for Cinema or TV Common Image Sizes (Pixel
Rows and Columns) 2K 2048 x 1556 1.33 Scan of
a 35MM Film frame 2K 2048 x 1080 1.89 Digital
Cinema Container 2K 2048 x 858 2.39 Digital
Cinema 2K 1998 x 1080 1.85 Digital Cinema 4K
4096 x 3112 1.33 Scan of a 35MM Film Frame 4K
4096 x 2160 1.89 Digital Cinema Container 4K
4096 x 1716 2.39 Digital Cinema 4K 3996 x
2160 1.85 Digital Cinema 4K 3840 x 2160 1.77
Super Hi Vision 8K 8192 x 4320 1.77 Super Hi
Vision Mega pixel Millions of Pixels 2048
Horizontal x 1080 Vertical 2.2 Megapixels 8192
Horizontal x 4320 Vertical 35.4 Megapixels
31
Sensor types triplet
  • 3-ccd dichroic block
  • Splits colours, shaping filters to trim
    responses
  • Long optical path length
  • Efficient use of light
  • Green half-pixel offset improves luma resolution
  • Will eventually go out of favour even for
    television

32
Sensor Types
  • Primary
  • Passes wanted light
  • absorbs the rest
  • Inefficient use of light
  • Secondary
  • More efficient light usage
  • more complex decoding

33
Progressive or Interlaced?
34
Cameras for HDTV or Digital Movies
35
Cameras for HDTV
  • Cinema
  • 35mm movie (24mm wide), 16mm (12mm wide) single
    sensor, uncompressed recording, very expensive
  • Broadcast Studio/OB
  • 2/3 (9.6mm wide), 3 sensor
  • Broadcast PSC
  • 2/3, 3 sensor, camcorder
  • Pro-sumer
  • 1/3 (4.8mm wide), 1 or 3 sensor, light-weight
  • Consumer
  • small, cheap, light, easy to operate
  • Specialist
  • variable speed, remote operation, infra-red, etc

36
Cameras for Cinema
  • Panavision Genesis
  • Super 35 format
  • 12.4M single sensor (5760x2160)
  • 1920x1080 to Sony HDCAM-SR
  • 10-bit log, 444/422
  • 150fps
  • 400ASA
  • Panavision 35mm movie lenses, means very
    expensive

37
Cameras for Cinema
  • Arri D21
  • Super 35 format (4-3)
  • 2880 x 2160 4-3 single Bayer sensor
  • 1920x1080 output
  • 12-bit Processing
  • 160fps _at_ 422
  • Scope Capable
  • Built to look/feel like a film camera,
    conventional rotating shutter, conventional 35mm
    movie lenses, 4-3 Sensor facilitates the use of
    Anamorphic Lenses

38
Cameras for Cinema
  • Thomson Viper Filmstream
  • 2/3 format B4 mount
  • 3 ccd, 1920x4320 (169)
  • 1920x1080 (169/2.371)
  • half-pixel offset
  • 10-bit log data or HD video
  • Conventional video design
  • Video lenses or film lenses modified for video,
    means cheaper, widespread use

39
Cameras for Cinema
  • RED
  • 4520 x 2580 CMOS Bayer
  • Super 35mm Sensor
  • Roving Specification
  • Sub optimum Dynamic range
  • Preprocesing required
  • Well marketed
  • Watch the all up price


40
Portable Cameras
  • Sony HDC 1500
  • New DSP
  • Power HAD EX CCD for high sensitivity, low noise
  • 14 bit A/D conversion
  • Super-sampled 720P operation
  • High sensitivity of F10 at 2000 lx and an
    excellent signal-to-noise ratio of 54 dB
    (typical)
  • No Triax until NAB

41
Cameras for Pro-sumer
  • Unfamiliar form less important
  • Must be smaller than digibeta size
  • Run long time on battery power
  • Records compressed video on cheap tape
  • Huge product market, so very low prices
  • GY-HD100, HVR-Z1, A1, HVX200 (XL1HD)

42
Cameras for Pro-sumer
  • Sony HVR-A1E
  • 1/3 cmos, 1920x1440 (43)
  • Integral Zeiss zoom
  • Very small/light (1.3kg)
  • Records 1080i/25 or 1080psf/25 on HDV tape
  • Records SD on DV tape
  • Popular replacement for PD170
  • XLR audio inputs
  • Very goodFilm mode, better than Z1, but
    generates alias on high-frequencies (i.e. lens is
    too sharp)

43
Lenses for HDTV
  • HDTV needs good lenses
  • 2/3 1920x1080 sensor has pixels at 5 micron
    spacing
  • so Disc of Confusion should be about 7 microns
  • 2/3 720x576 sensor has pixels at 11 micron
    spacing
  • so Disc of Confusion should be about 15 microns
  • HD lenses have to be twice as sharp, for
    1920/width
  • 167lp/mm, 2/3100lp/mm, 1/2133lp/mm,
    1/3200lp/mm
  • (35mm40lp/mm, 16mm80lp/mm)
  • HD programme-makers are more critical of quality
  • HD images are expected to be more contrasty
  • so lenses must be overall better quality, low
    flare

44
Lenses for HDTV
  • Zooms for convenience
  • Film-style are bare
  • measure focus from image plane
  • needs Focus Puller
  • popular in Drama
  • Video-style have servo packs
  • focus from front element
  • can be easier to use
  • Canon, Fuji, Angenieux, Arri, Optex, Cooke,
    Panavision

45
Lenses for HDTV
  • Back focus setting
  • Ensures that image is focused on the sensor
    correctly
  • Keeps focus markings accurate, keeps focus during
    zoom
  • Critical on video cameras, optical path length
    varies (48mm)
  • Do it when changing lenses, unless using
    calibrated Zeiss primes temperature changes
    significantly
  • Use proper test chart, or a lens collimator
    (Zeiss, Century)
  • Biggest problem on Panavised Cinealta HDW-F900
  • Not needed on film cameras because dimensions are
    standardised, 52mm20µm

46
Camera ShutteringUse with care, getting this
wrong cannot be fixed in post
  • FILM
  • TV
  • needs shutter so that film can advance, 180
    usual
  • Mechanical rotating shutter in camera, and
    Arri/Panavision
  • needs shutter only for film-style, or for sharp
    slomotion
  • Also for shooting cyclically lit scenes, e.g.
    tv/computer screens
  • Achieved electronically, by deliberately
    discharging the sensor early, then letting it
    accumulate charge for reading out

47
Setting a camera
  • Theres a lot to get wrong
  • Top Cameras now 14 bit process

48
Basic Camera Processor Controls
  • Black Balance
  • White Balance
  • Gamma
  • Painting
  • Details Gain
  • Used in conjunction with filters
  • Memory Card storage for DP

49
Line up Charts
50
Tape Recorders
  • HD-Cam
  • 311 Subsampled1440 x 1080
  • 7-1 compression
  • 8 Bit
  • HD-CAM SR
  • 422 or 444
  • 440 or 880 Mbps
  • 10Bit
  • Flexible modes

51
Disk Recorders
  • BBC Ingex
  • Open technology Multiple Channel
  • Uses mid range workstaion with capture card
  • 422, flexible parameters
  • 8 Channels SDI, 2 Channels of HD
  • http//ingex.sourceforge.net/
  • Codex Digital
  • Ruggedised Hard drive
  • Flexible Parameters
  • http//www.codexdigital.com/technical/page3.php

52
P2 Memory Cards
  • Card Bus PC Standard to allow direct connection
    to Laptop
  • 4 x SD cards inside to facilitate high data rate
  • Up to 64 GB today
  • Rugged with wide temperature range
  • Data wrapped in MXF for instant use
  • Metadata Capability
  • Low cost card availiable (Lower Lifetime)

53
Sony SXS Pro Card
  • Express card Based
  • Up to 32GB
  • 500 Mbps Transfer rate
  • For Sony XD Cam
  • Based on new PCMSIA Express card
  • Adaptor needed for older laptops

54
Disks
  • Sony XD Cam
  • Optical Disk
  • Storage capacity of 50 GB
  • More than 4 hours of HD content
  • Data Cam E2 Disks
  • Capacity 500GB
  • Max Data Rate 750 Mbps
  • Anti Shock up to 900G
  • Interchangeable with E2 Card

55
Displays The Cathode Ray Tube
  • Originated late 19th Century
  • Used for TV from mid 1930s
  • Colour available from early 1950s
  • The heart of the CRT is an Electron Gun
  • The Electron gun shoots electrons at a phosphor
    coating which glows
  • Colour tubes have three guns and a mechanical
    separator

56
CRT
57
Why Does the Obsolete CRT Matter?
  • All TV systems are designed around CRT
    Characteristics
  • The CRT is not a Linear Device
  • The CRT is Analogue
  • Professional CRT Phosphors match ITU 709
  • The CRT Gamma curve depends on room brightness
  • All TV is WYSIWYG using calibrated monitors and
    Cameras

58
Gamma
CRT Gamma
  • Gamma typically 2.3
  • End to end Gamma 1.2
  • High Black gain Noise
  • Number range 64-940
  • R,GB should track
  • Grade 1 monitor 200cd/m2
  • Use Pluge to set black point


Camera Gamma
59
Resolution
  • CRT is analogue
  • HD Theoretical bandwidth limit 30 Mhz
  • Sony Grade 1 CRT 23 23 MHz
  • Digital Displays subject to Nyquist
  • Bandwidth lt2 x sample rate
  • Pixel numbers do not Resolution directly
  • HD clock 74.25 Mhz / 2 37.125- 20 29.7 Mhz
  • Sample grid 1920 x 1080 or 1280 x 720
  • Same clock for 1080I and 720P
  • Many panels dont match transmission grid
  • Beware of overscan

60
LCD
  • Backlight sets pixel colour
  • Pixel pass through Analogue
  • Modulation by Polarisation change
  • Early versions limited by bit depth
  • Modulation linear
  • No Burn in
  • Poor Backlight purity possible


61
Thank You
  • Peter Wilson
  • EDCF
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