Multimedia applications
Transcript of Multimedia applications
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Multimedia Applications
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Video
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OverviewOverview• Using video.• How video works?• Broadcast video standards.• Analog video.• Digital video.• Video recording and tape formats.• Shooting and editing video.• Optimizing video files for CD-ROM.
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VideoVideo• Video is the most recent addition to the
elements of multimedia
• It places the greatest demands on the computer and memory (using about 108 GB per hour for full motion)
• Often requires additional hardware (video compression board, audio board, RAID - Redundant Array of Independent Disks- for high speed data transfer)
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Using VideoUsing Video
• Carefully planned video can enhance a presentation (e.g. film clip of JFK, better than an text box of same message)
• Before adding video to a project, it is essential to understand the medium, how to integrate it, its limitations, and its costs
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Using Digital VideoUsing Digital Video
• Digital video has replaced analog as the method of choice for making and delivering video for multimedia.
• Digital video device produces excellent finished products at a fraction of the cost of analog.
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Using Digital VideoUsing Digital Video
• Digital video eliminates the image-degrading analog-to-digital conversion.
• Many digital video sources exist, but getting the rights can be difficult, time-consuming, and expensive.
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Video ClipsVideo Clips• Ways to obtain video
– shoot new film clips with a digital camcorder
– convert you own video clips to digital format– acquire video from an archive - often very
expensive, difficult to obtain permissions or licensing rights
• Be sure to obtain permission from anyone you film or for any audio you use!
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How Video WorksHow Video Works
• Light passes from an object through the video camera lens and is converted into an electrical signal by a CCD (charge-coupled device).
• High quality cameras have 3 CCD• Signal contains 3 channels of color
information (red, green, blue) and a synchronization pulse.
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How Video WorksHow Video Works• If each channel of a color signal is separate
it is called RGB ( preferred)
• A single composite of the colors and sync signal is less precise
• A typical video tape has separate tracks for audio, video, and control
• ( See p. 192)
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How Video WorksHow Video Works• The video signal is magnetically written to
tape by a spinning recording head following a helical path
• Audio is recorded on a separate straight track
• The control track regulates the speed and keeps the tracks aligned as the tape plays/records.
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Video BasicsVideo Basics
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Broadcast Video StandardsBroadcast Video Standards
• NTSC
• PAL
• SECAM
• HDTV Six different formats
Aspect ratio is 16:9
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Broadcast Video StandardsBroadcast Video Standards
National Television Standards Committee (NTSC):– These standards define a method for
encoding information into electronic signal that creates a television picture.
– It has screen resolution of 525 horizontal scan lines and a scan rate of 30 frames per second.
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Broadcast Video StandardsBroadcast Video Standards• NTSC - National Television Standards
Committee - 1952, (“never the same color”)
• 1 frame = 525 horizontal lines every 1/30 second
• 2 passes - odd/even lines, 60/second(60 Hz)
• interlacing - to reduce flicker
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Broadcast Video StandardsBroadcast Video Standards
Phase Alternate Line (PAL) and Sequential
Color and Memory (SECAM):
• PAL has a screen resolution of 625 horizontal lines
and a scan rate of 25 frames per second.
• SECAM has a screen resolution of 625 horizontal
lines and is a 50 Hz system.
• SECAM differs from NTSC and PAL color systems
in its basic technology and broadcast method.
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Broadcast Video StandardsBroadcast Video Standards
Advanced Television Systems Committee (ATSC) Digital Television (DTV):
• This digital standard provides TV stations with sufficient bandwidth to present four or five Standard Television (STV) signals or one High Definition TV (HDTV) signal.
• This standard allows for transmission of data to computers and for new Advanced TV (ATV) interactive services.
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Broadcast Video StandardsBroadcast Video StandardsSeveral incompatible standards:• NTSC (US, Japan, many other countries)
• PAL - (United Kingdom, parts of
Europe, Australia, South Africa)
• SECAM - (France Russia, few others)
• HDTV - ( US ) - newest technology
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Broadcast Video StandardsBroadcast Video Standards• HDTV- High Definition Television now
available, allow viewing of Cinemascope and Panavision movies with aspect ratio 16:9 ( wider than high) (See p. 200)
• Twice the resolution, interlaced format
• Digitized then compressed for transmission
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Broadcast Video StandardsBroadcast Video Standards
• 4: 3 Aspect Ratio
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Broadcast Video StandardsBroadcast Video Standards
• 16: 9 Aspect Ratio
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Integrating Computers and Integrating Computers and TelevisionTelevision
• Television video is based on analog technology and international broadcast standards
• Computer video is based on digital technology and other image display standards
• DVD and HDTV merges the two
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Analog VideoAnalog Video– Analog television sets remain the most widely
installed platforms for delivering and viewing video.
– Television sets use composite input. Hence colors are less pure and less accurate than computers using RGB component.
– NTSC television uses a limited color palette and restricted luminance (brightness) levels and black levels.
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Analog VideoAnalog Video
– Some colors generated by a computer that display fine on a RGB monitor may be illegal for display on a NTSC TV.
– While producing a multimedia project, consider whether it will be played on a RGB monitor or a conventional television set.
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Video Overlay SystemVideo Overlay System• To display analog video (TV) images on a
computer monitor, the signal must be converted from analog to digital form ( Where else does this conversion commonly take place?)
• A special digitizing video overly board is required for the conversion
• Produces excellent quality, full screen, full motion video, but costly.
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Video Overlay SystemVideo Overlay System
• Many companies use computer based training (CBT) systems
• These require a computer and monitor cabled to a TV and video disc player.
• Overlay boards allow the video disc to be controlled by the computer and display the images on the computer screen.
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Video Capture BoardsVideo Capture Boards• Video overlay boards can capture or
digitize video frames and play them back as QuickTime MPEG and AVI movies.
• Some also include audio input and sound management to interleave sound and images
• Some also offer compression and accelerate digitizing, or support NTSC video.
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Differences Between Computer Differences Between Computer and TV Videoand TV Video
• Computer scan refresh rate = 480 lines/sec
• Computer scan is progressive ( non-interlaced) at 66.67 HZ or higher
• TV scans at 525 (or 625) lines/sec, with interlacing at a frame rate of 60 Hz
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Interlacing EffectsInterlacing Effects• The TV electron beam actually “draws all the
odd line, then all the even lines, interlacing them
• On a computer (RGB) monitor, lines are painted one pixel thick and are not interlaced. Displayed on a TV they “flicker” because they appear in every other field. To avoid this avoid very thin lines and elaborate serifs.
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Differences Between Differences Between Computer and TV VideoComputer and TV Video
• TV broadcasts an image larger than the screen so that the “edge” of the image is against the edge of the screen. This is called overscan
• Computer images are smaller than the screen area (called underscan) and there is a border around the image
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Computers and VideoComputers and Video
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Differences Between Differences Between Computer and TV VideoComputer and TV Video
• When a computer screen is converted to video the outer edges do not fit on the TV screen only about 360-480 lines of the computer image are visible.
• Avoid using the outer 15% of the screen for graphics, or titles for use on TV
• Use the safe title area
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Video ColorVideo Color
• Color reproduction and display are also different in TV and computers monitors
• Computers use RBG component video and produce more pure color
• NTSC TV uses a limited color palette and restricted luminance (brightness) and black levels
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Working with Text and Titles for Working with Text and Titles for Video ProductionsVideo Productions• Use plain, bold, easily read fonts
• Use light color text on a dark background
• Avoid color combinations like yellow/violet, blue/orange which “vibrate”
• Avoid black or colored text on white background
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Working with Text and Titles Working with Text and Titles for Video Productionsfor Video Productions
• Make lines and graphics at least two pixels wide
• Use parallel lines and boxes sparingly and draw them with thick lines
• Avoid “hot” colors
• Keep graphics and titles in the safe screen area
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Working with Text and Titles for Working with Text and Titles for Video ProductionsVideo Productions
• Bring titles on slowly and let them remain on the screen sufficiently long, fade out
• Avoid “busy” screens- use additional pages instead
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Digital VideoDigital Video
• Digital video architecture.
• Digital video compression.
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Digital Video ArchitectureDigital Video Architecture
• Digital video architecture consists of a format for encoding and playing back video files by a computer.
• Architecture includes a player that can recognize and play files created for that format.
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Digital Video CompressionDigital Video Compression• Digital video compression schemes or
“codec's” ( coder/decoder) is the algorithm used to compress (code) a video for delivery.
• The codec then decodes the compressed video in real-time for fast playback.
• Streaming audio and video starts playback as soon as enough data has transferred to the user’s computer to sustain this playback.
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Video CompressionVideo Compression• To store even a 10 second movie clip requires
the transfer of an enormous amount of data in a very short time
• 30 seconds of video will fill a 1 GB hard drive
• Typical hard drives transfer about 1MB/second and CD- ROMs about 600K/second
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Video CompressionVideo Compression• Full motion video requires the computer to deliver
the data at 30 MB/second more than today’s PCs and MACs can handle
• Solution- use video compression algorithms or codec's
• Codec's compress the video for delivery and then decode it for playback at rates from 50:1 to 200:1
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Video Compression & StreamingVideo Compression & Streaming• Codecs ( such as MPEG, JPEG) use lossy
compression schemes
• Streaming technologies are also used to provide reasonable quality , low-bandwidth on the WEB
• Playback starts as soon as enough data have been transferred to the user’s computer instead of waiting for the whole file to download
• ( RealAudio and RealVideo software)
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MPEGMPEG
• Standard developed by the Moving Pictures Experts Group for digital representation of moving pictures and associated audio
• http://mpeg.org
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Digital Video CompressionDigital Video Compression• MPEG is a real-time video compression algorithm.
(Moving Picture Experts Group)
• MPEG-4 (1998-1999) includes numerous multimedia capabilities and is a preferred standard.
• MPEG-7 (2002) (or Multimedia Content Description Interface) integrates information about motion video elements with their use.
• MPEG –21 under development
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Digital VideoDigital Video
• Video clips can be shot or converted to digital format and stored on the hard drive.
• They can be played back without overlay boards, second monitors or videodiscs using QuickTime or Active Movie for Windows
• Analog video can be converted to digital or now created in digital form
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Video Recording and Tape Video Recording and Tape FormatsFormats
• Composite analog video.
• Component analog video.
• Composite digital.
• Component digital.
• ATSC digital TV.
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Composite Analog VideoComposite Analog Video• Composite video combines the luminance and
chroma information from the video signal.
• Composite video produces lowest quality video and is most susceptible to generation loss.
• Generation loss is the loss of quality that occurs while moving from original footage to editing master to copy.
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Component Analog VideoComponent Analog Video• Component video separates the luminance and
chroma information.
• It improves the quality of the video and decreases generation loss.
• In S-video, color and luminance information are kept on two separate tracks (Y/C) to improve the picture quality.
• Betacam is a new portable professional video format which lays the signal on the tape in three component channels.
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Composite DigitalComposite Digital
• Composite digital recording formats combine the luminance and chroma information.
• They sample the incoming waveforms and encode the information in binary (0/1) digital code.
• It improves color and image resolution and eliminates generation loss.
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Component Digital Component Digital • Component digital formats add the advantages of
component signals to digital recording.
• D-1 component digital format is an uncompressed format which has a very high quality image.
• It uses a 19 mm (3/4-inch) tape in order to save data.
• Several other digital component formats are DCT, Digital Betacam, DV format, DVCPRO, and DVCAM formats.
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ATSC Digital TVATSC Digital TV
• These standards provide for digital STV and HDTV recordings that can be broadcast by digital TV transmitters to digital TV receivers.
• ATSC standards also provide for enhanced TV bringing the interactivity of multimedia and the Web to broadcast television.
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Vaughn’s Law of Multimedia Vaughn’s Law of Multimedia MinimumsMinimums• Your goal is to produce multimedia that is
adequate and does it’s job but doesn’t throw you into bankruptcy.
• Experiment with various levels of consumer grade equipment
• Professional sound and video equipment is very expensive
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Recording FormatsRecording Formats• S-VHS and Hi-8 consumer quality
• Component (YUV) - Sony BetacamSP the professional standard for broadcast quality
• Component Digital- a digital version of the Betacam- best format for graphics > $900,000 and produces 15 minutes of video
• Composite Digital most common >$110,000
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Shooting & Editing VideoShooting & Editing Video
• Shooting platform– use a steady tripod– or a camera with an electronic image
stabilization feature to avoid “shaky hand effect”
– or use camera moves and moving subjects to disguise your lack of steadiness
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Shooting & Editing VideoShooting & Editing Video
• Lighting performance is the main difference between professional and consumer camcorders
• Use a simple floodlight kit or natural daylight to improve the image
• Onboard flood lights can be used as fill light to illumine faces
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Shooting & Editing VideoShooting & Editing Video
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Shooting & Editing VideoShooting & Editing Video
• Chroma Key or Blue Screen - popular technique for making multimedia without the use of expensive backgrounds
• In shooting against a blue screen, be sure that the lighting is perfectly even and that actors are not too close to the screen so that color “spills” over on them
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Shooting & Editing VideoShooting & Editing Video
• Composition– Avoid wide panoramic shots– Use close-ups, head and shoulders– Remember the more a scene changes the
slower the playback will be– Keep the camera still, let the subject add
the motion by walking, turning...
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Using Video TapesUsing Video Tapes• Fast forward new tapes and rewind them so
that the tension is even (called “packing”)
• Black-stripe the tape by running it through the recorder with the lens cap on -eliminates “snowy noise”
• Do not reuse tapes after editing
• Remove break off tab to avoid overwriting
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Video Hardware ResolutionVideo Hardware Resolution
• Horizontal resolution -the number of lines of detail the camera can reproduce
• Different from the vertical scan lines on TV
• The lens, and number, size and quality of the CCDs determine the resolution
• Poor resolution = poor image
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Consumer Grade EquipmentConsumer Grade Equipment
• Mass production at low cost; easier to use
• Cameras and camcorders that use HI-8 and S-VHS formats are superior to 8 mm and VHS systems
• HI-8 is most widely available tape format and best consumer grade
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Making Tape CopiesMaking Tape Copies• For demo or promo tapes use at least Super
VHS ( HI-8 is best and allow unlimited copies to be made without degradation)
• Copying ( dubbing) depends on the tape format and the quality of the equipment being used
• Copy in SP mode- faster writing produces better images
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Video Window SizeVideo Window Size
• Shrinking a digitized image improves it perceived sharpness
• ( Also happens when you switch from 19” to 13” TV)
• The image is crisper because the scan lines are closer together
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Editing with Consumer VCRsEditing with Consumer VCRs
• Editing with 2 VCRs causes problems because the two machines are not in sync
• Editing software, such as Premier, or After Effects, has become more commonly used in multimedia
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Video Conferencing Video Conferencing
• Video telephone conferencing standard for compressing audio and motion video images
• Encodes audio and video for transmission over copper or fiber optic lines
• Other compression systems are currently being developed by Kodak, Sony, etc.
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Optimizing Video files for CD-ROMsOptimizing Video files for CD-ROMs
• CD- ROMs are an excellent distribution media for multimedia: inexpensive, store great quantities of information, with adequate video transfer rates
• Suitable for QuickTime and AVI file formats as well as those produced by Director, etc.
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Optimizing Video files for CD-ROMsOptimizing Video files for CD-ROMs
• Limit the synchronization between video and audio– AVI interleaves them– QuickTime files must be “flattened” - to
interleave the audio and video
• Use regularly spaced key frames (10 to 15 frames apart)
• Limit the size of the video window- the more data the slower the playback
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Optimizing Video files for CD-ROMsOptimizing Video files for CD-ROMs
• Choose the software compression algorithm carefully– Sorenson codec is optimized for CD-
ROM playback– Cinepack algorithm, available with AVI
and QuickTime, is also optimized for CD-ROM playback
– Use Norton speed Disk to defragment your files before burning the master
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SummarySummary• Various video standards are NTSC,
PAL, SECAM, and ATSC DTV.
• Categories of video standards are composite analog, component analog, composite digital, and component digital.