multimedia applications

Multimedia Applications

Video

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.

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)

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

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.

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.

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!

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.

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)

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.

Video BasicsVideo Basics

Broadcast Video StandardsBroadcast Video Standards

• NTSC

• PAL

• SECAM

• HDTV Six different formats

Aspect ratio is 16:9

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.

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

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.

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.

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

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

Broadcast Video StandardsBroadcast Video Standards

• 4: 3 Aspect Ratio

Broadcast Video StandardsBroadcast Video Standards

• 16: 9 Aspect Ratio

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

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.

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.

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.

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.

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.

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

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.

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

Computers and VideoComputers and Video

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

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

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

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

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

Digital VideoDigital Video

• Digital video architecture.

• Digital video compression.

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.

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.

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

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

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)

MPEGMPEG

• Standard developed by the Moving Pictures Experts Group for digital representation of moving pictures and associated audio

• http://mpeg.org

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

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

Video Recording and Tape Video Recording and Tape FormatsFormats

• Composite analog video.

• Component analog video.

• Composite digital.

• Component digital.

• ATSC digital TV.

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.

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.

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.

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.

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.

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

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

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

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

Shooting & Editing VideoShooting & Editing Video

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

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...

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

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

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

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

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

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

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.

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.

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

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

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.