UNDERSTANDING HDTV TECHNOLOGY

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UNDERSTANDING HDTV TECHNOLOGY

• By Peter Wilson, HDDC

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The Seminar

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

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HD History
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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

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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

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NHK fundamental research
HDTV
NTSC
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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
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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

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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
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Interlaced Progressive
Interlace Scan
Progressive Scan
Field 1
Field 2
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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
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Segmented Frame Format
Field 1
Distribute as 2 Interlaced Fields
Scan as 1 Progressive Frame
Field 2
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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
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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
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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
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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)
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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.
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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)

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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
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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
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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
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Dual Link 372M
Dual 1.485Gbit/s 292M interface High frame rate
progressive 422 YCbCr Interlaced 4444
12-bit formats Alpha channel
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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

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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

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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

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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

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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

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Compression formats
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Chroma Subsampling
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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

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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
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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

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Sensor Types

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

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Progressive or Interlaced?
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Cameras for HDTV or Digital Movies
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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

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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

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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

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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

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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

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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

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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)

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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)

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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

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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

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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

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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

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Setting a camera

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

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Basic Camera Processor Controls

• Black Balance
• White Balance
• Gamma
• Painting
• Details Gain
• Used in conjunction with filters
• Memory Card storage for DP

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Line up Charts
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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

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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

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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)

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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

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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

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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

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CRT
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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

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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
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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

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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

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Thank You

• Peter Wilson
• EDCF