Transcript HDTV Bringing TV One Step Closer to Film HDTV - Bringing TV One Step Closer to Film • • • • • History of TV Standards Technical Aspects Implementation Impact.

HDTV
Bringing TV One Step Closer to Film
HDTV - Bringing TV
One Step Closer to Film
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History of TV
Standards
Technical Aspects
Implementation
Impact
History of TV
• 1842 Alexander Bain managed to transmit a
still image over wire. First fax machine!
• In 1884 Paul Gottlieb Nipkow went a step
further, and discovered (and patented) a way
to scan a moving image and transmit it
sequentially. Birth of mechanical television.
Mechanical Television
Mechanical Television
John Logie Baird, a Scottish
inventor, demonstrated what
many refer to as the first
television broadcast on
January 26, 1926. Baird’s
grayscale image, presented to
members of the Royal
Institution in London had
only about 30 lines of
resolution.
First “mass produced” TV set
Mechanical Television
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1927 - First TV broadcast in the US
Herbert Hoover
From NY to Washington
Had about 50 scanning lines
Broadcast by wire and radio
Electronic Television
• 1934 Philo Farnsworth
demonstrated an allelectronic system
• Less cumbersome than
mechanical TV
• Quickly gained
popularity
The search for standards:
the FCC & the NTSC
• FCC Established by the Communications
Act of 1934
• Radio Manufacturers Association (RMA)
recommended a standard for television
using 441 horizontal scan lines and 30
frames per second with a 4:3 aspect ratio
The search for standards:
the FCC & the NTSC
• FCC urged the RMA to form the National
Television System Committee (NTSC) in 1940
• 1941 - NTSC established its first set of standards,
which kept the 4:3 aspect ratio but called for a
higher resolution image with 525 scan lines
refreshing at a rate of 30 interlaced frames, or 60
fields per second. (263 lines followed by 262)
The search for standards:
the FCC & the NTSC
• FCC allotted 6 MHz slices of bandwidth to
TV stations.
• Eventually covered a frequency range
spanning from 54 MHz to 890 MHz on the
broadcast spectrum
The search for standards:
the FCC & the NTSC
• 1950s brought the addition of color (Home
viewing was brought a step closer to cinema)
• 1953 - The NTSC standard had to be revised
The search for standards:
the FCC & the NTSC
• 1953 - The NTSC standard had to be revised to adapt to
color TV.
• Engineers split the signal into two components: luma,
which contained the brightness information, and
chrominance, which contained the color information.
• Field refresh rate of 60 Hz was slowed down by a factor of
1000/1001 to 59.94 Hz.
• Broadcast television downshifted from 30 to 29.97 frames
per second
Same old standard
(The song remains the same)
• Many improvements were made in cameras,
production and broadcast gear, and in television
receivers
• Despite advances, the quality of analog broadcast
was still limited to the NTSC standard of 60 fields
and 525 horizontal scan lines
• Stuck with more or less same standards created in
1941.
Same old standard
(The song remains the same)
• By the 1980s, manufacturers had been
developing and using both analog and digital
HD systems
• It became clear that the replacement for
analog would use digital television
technology.
• Needed a new set of standards to ensure
compatibility.
ATSC
• Formed in 1982
• The Advanced Television Systems Committee is a
not-for-profit organization whose purpose is to
develop standards for the transition to DTV.
• Its published broadcast standards are voluntary
unless adopted and mandated by the FCC.
• ATSC proposed DTV Standard (A/53) that
specifies the protocol for high-definition
broadcasting through a standard 6MHz channel
DTV
• In December 1996, the FCC adopted
standards proposed by the ATSC, mandating
that broadcasters begin broadcasting
digitally.
• WRAL of Raleigh, North Carolina was the
first station to broadcast in digital.
DTV
• FCC’s current plan is to terminate analog
broadcasting by February 2009 (though the
deadline could be extended).
DTV, SDTV, & HDTV
• NTSC standards defined one analog format
• ATSC created a framework supporting
multiple digital formats
• There is considerable confusion among
consumers regarding SDTV, DTV and
HDTV.
• Broadcaster do not have to broadcast in HD,
just in DTV.
DTV formats
HDTV/SD Horizontal
TV
lines
Vertical
lines
Aspect
Ratio
Frame Rate
SDTV
640
480
4:3
60p, 60i, 30p,
24p
SDTV
704
480
4:3 and
16:9
60p, 60i, 30p,
24p
HDTV
1280
720
16:9
60p, 30p, 24p
HDTV
1920
1080
16:9
60i, 30p, 24p
Note: Non-integer formats (eg. 29.97) omitted for clarity.
HDTV & SDTV Comparison
• Judging simply on pixel count, a 1080i
HDTV image is 6 - 9 times better than a
standard, NTSC image
• Audio is also improved. The ATSC standards
call for AC3 or Dolby Digital sound, which
can provide 24-bit 5.1 surround sound
HDTV & SDTV Comparison
Technical Aspects
Technical Aspects
• Codec is short for compressor-decompressor or
coder-decoder, and refers to a manner in which
data is compressed and uncompressed
• Broadcast and production codecs differ
• In order to squeeze the data into a form that can be
reliably broadcast within a 6 MHz section of
bandwidth, the HDTV signal must be compressed
at about a 50:1 ratio.
Technical Aspects
• Most DTV broadcasts (terrestrial, cable &
satellite) use MPEG-2
• MPEG-2’s compresses the video into groups of
pictures (GOPs) not individual frames. Images are
divided into macroblocks, which are areas of 16 x
16 pixels.
• GOPs are created with three types of pictures: I, P,
and B frames. I frames are intracoded frames. P
are predicted frames and B are bidirectional
frames.
Technical Aspects
• In addition to audio & video, DTV contains
metadata - auxiliary information related to
the program or its content including audio
dialog level info, closed captioning, format
descriptor tags, and digital rights
management (DRM) data.
Technical Aspects
• HDTV allows for both interlaced and
progressive content.
Technical Aspects
Interlaced display
Technical Aspects
• DTV supports multiple frame rates including 24p.
• 24p is the standard film frame rate used by the motion
picture industry for years
• Allows for easier transfer to / from film
• 16 x 9 aspect ratio more closely matches widescreen
film formats.
• DTV supports the display of traditional, standard
resolution, 4:3 content.
Aspect ratios
Conversion
• Up-converting (converting to a superior format)
• Down-converting (converting to a lesser format)
• Scaling / sizing
• Aspect ratio manipulation / conversion
• Common to see broadcasters delivering images
with the improper aspect ratio.
Frame rate conversion - 3-2 pulldown
Used to convert film or 24p to interlaced 29.97
Implementation
Implementation
• HDTV production typically begins with a highdefinition camera, or a project shot on film then
converted to a digital format.
• Other means are possible. Much of Tim Burton’s
recent stop-motion feature, The Corpse Bride was
shot with a Canon digital still camera, and then
transferred to digital video for editing.
• Many commercials, cartoons, and full-length
features have been created solely with animation
software
Implementation - Cameras
• HDTV cameras have been used for private
applications long before the ATSC standards were
in place
• Higher-end production cameras suitable for studio
or digital cinematography can cost well over
$100,000. (That’s not including the lens!)
• Sub-$1,000 range targeted to consumers are
pushing sales on the lower end.
Implementation - Cameras
• Star Wars Episode III was shot with a Sony HDC-F950
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Implementation
Recording & playback can be done in
many ways:
• Tape
• Hard-drive
• Optical disc
• RAM
Implementation - recording & playback
• D-VHS – This consumer format from JVC records onto
VHS tapes using an MPEG-2 stream at up to a 28.2 Mbps
data rate
• HDV – Canon, Sony and JVC offer relatively lower cost
cameras that record at a maximum resolution of 1440 x
1080. HDV uses a form of MPEG-2 compression that
results in a 25 Mbps signal that can be recorded onto
miniDV cassettes.
• DVCPRO HD – Also known as D12, DVCPRO HD was
developed by Panasonic and has versions that record on
magnetic tape as well as memory cards.
Implementation - recording & playback
• XDCAM HD - Sony’s tapeless format records onto BluRay optical discs using several possible codecs. It can
record HD content using MPEG-2 encoding at up to 35
Mbps or DV25 for DVCAM, and MPEG-4
• D-5 HD – Developed by Panasonic in 1991, the D-5 format
has been updated to HD. Handles 720 and 1080 content at
most possible frame rates.
• HDCAM - Sony’s format records onto 1/2” videocassettes
at a number of possible frame rates. It uses a 593 Mbps data
rate and supports up to 8 channels of audio.
• HDCAM SR - data rates up to 8800 Mbps with up to 12
audio channels
Implementation - Editing
• MPEG-2 works well for transmission, but is not
an ideal choice for editing due to its GOP structure
and high compression ratio.
• Editors typically want access to discreet frames
with less compression.
• In addition to the standard bit depths of 8 and 10,
there are also higher end, 16-bit codecs available
from companies like Pinnacle and Digital Anarchy
Implementation - Editing storage
• HD content, especially uncompressed, takes
massive amounts of bandwidth and disk space.
Consider this comparison:
• An hour of DV footage with a stereo pair of 16-bit
audio tracks takes approximately 14 GB of disk
space.
• An hour of 10-bit 1920 x 1080 HD footage with a
pair of 24-bit audio channels requires nearly 600
GB of space.
Implementation - Display technologies
• CRT - CRT monitors draw the lines one after the next,
from top to bottom to make an entire frame. Generally
speaking they have pleasing color balance performance
and wide viewing angles. Because of their use of vacuum
tubes, the displays can’t be constructed much larger than
40” or so.
• LCD – LCD HDTV monitors work by casting light
through an array of cells sandwiched between two
polarized planes. LCD monitors are less expensive than
CRTs to manufacture and come in both flat panel and rear
projection varieties. Flat panel, direct-view monitors have
become popular as computer and DTV monitors as they
are bright, use less electricity than CRTs, and have a
relatively long life span.
Implementation - Display technologies
• Plasma – Like LCD monitors, plasma HDTV sets are thin
and are made up of cells that correspond to pixels sandwiched
between glass plates. Plasma cells contain three separate gasfill sub-cells, one for each color. When a current is applied to
a sub-cell, it ionizes the gas emitting ultraviolet light. The
ultraviolet light in turn excites fluorescent substances in the
sub-cells that emit red, blue or green light.
• DLP – Digital light processing is a technology used in
projection displays. In DLP monitors, light is reflected off an
array of microscopic hinged mirrors. Each tiny mirror
corresponds to a visible pixel. The light is channeled through
a lens onto the surface of the screen. Single chip DLP
projectors can display 16.7 million colors. 3-chip projectors
can display 35 trillion colors.
Implementation - Display technologies
• LCoS – Similar to DLP, LCoS projection systems use
liquid crystals instead of mirrors to block light. The
liquid crystals are arranged in a grid in front of a highly
reflective surface.
Usage/Saturation
• A recent survey carried out by Panasonic in
December of 2005 reported that 26% of US
households will own or will purchase a highdefinition set by the end of 2006.
• The NAB (National Association of Broadcasters)
maintains a growing list of stations that have made
the move to digital broadcast. In December 2005,
1,550 stations were broadcasting digitally.
Impact of HDTV
• Broadcasters & consumers spend more $
• Increased visual clarity has forced designers to spend
considerably more money on sets, set dressings and
props
• DVD battle being waged.
•Blu-Ray vs HD-DVD
Conclusion
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As NTSC retires, HDTV programming, products, and
production services will continue to grow exponentially.
Move will be cheaper, quicker, and easier as products and
services become more widespread and people grow
accustomed to the new technology.
HDTV has brought a more cinematic experience into
viewer’s homes and with digital cinema, delivered the film
industry a few of the benefits of television. However,
HDTV still has much lower resolution than 70mm film.
It’s a matter of time before some will begin pressuring for
another increase in quality.