HDTV - Bringing TV One Step Closer to Film History of TV Standards Technical Aspects Implementation Impact
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. History of TV
John Logie Baird, a Scottish inventor, demonstrated what many refer to as the first television broadcast on January 26, 1926. Bairds grayscale image, presented to members of the Royal Institution in London had only about 30 lines of resolution. Mechanical Television
1927 - First TV broadcast in the US Herbert Hoover From NY to Washington Had about 50 scanning lines Broadcast by wire and radio Mechanical Television
1934 Philo Farnsworth demonstrated an all- electronic system Less cumbersome than mechanical TV Quickly gained popularity Electronic Television
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 FCCs 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 TV Horizontal lines Vertical lines Aspect Ratio Frame Rate SDTV6404804:360p, 60i, 30p, 24p SDTV7044804:3 and 16:9 60p, 60i, 30p, 24p HDTV128072016:960p, 30p, 24p HDTV1920108016:960i, 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
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-2s 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 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.
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.
HDTV production typically begins with a high- definition camera, or a project shot on film then converted to a digital format. Other means are possible. Much of Tim Burtons 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. (Thats 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
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 - Sonys tapeless format records onto Blu- Ray 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 - Sonys 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
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
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 - Editing storage
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 cant 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 gas- fill 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. Implementation - Display technologies
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 high- definition 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 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 viewers 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. Its a matter of time before some will begin pressuring for another increase in quality.
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