Title: COM 205 Multimedia Applications
1COM 205Multimedia Applications
- St. Josephs College
- Fall 2004
2Chapter 8
3Overview
- 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.
4Video
- 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)
5Using Video
- Carefully planned video can enhance a
presentation (eg. 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
6Using 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.
7Using 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.
8Video 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!
9How 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.
10How 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. 180)
11Video Basics
12How 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.
13Video Basics
14Broadcast Video Standards
- NTSC
- PAL
- SECAM
- HDTV
- Six different formats
- Aspect ratio is 169
15Broadcast 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.
16Broadcast 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
17Broadcast 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.
18Broadcast 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.
19Broadcast Video Standards
- Several 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
20Broadcast Video Standards
- HDTV- High Definition Television now available,
allow viewing of Cinemascope and Panavision
movies with aspect ratio 169 ( wider than high)
(See p. 184) - Twice the resolution, interlaced format
- Digitized then compressed for transmission
21Broadcast Video Standards
22Broadcast Video Standards
23Integrating Computers and Television
- 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
24Analog 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.
25Analog 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.
26Video 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.
27Video 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.
28Video 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.
29Differences Between Computer and 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
30Interlacing 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.
31Differences Between Computer 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
32Computers and Video
33Differences Between Computer 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 ( See p. 184)
34Video 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
35Working with Text and Titles for Video 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
36Working with Text and Titles for 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
37Working with Text and Titles for Video Productions
- Bring titles on slowly and let them remain on the
screen sufficiently long, fade out - Avoid busy screens- use additional pages
instead
38Digital Video
- Digital video architecture.
- Digital video compression.
39Digital 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.
40Digital Video Compression
- Digital video compression schemes or codecs (
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 users
computer to sustain this playback.
41Video 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
42Video Compression
- Full motion video requires the computer to
deliver the data at 30 MB/second more than
todays PCs and MACs can handle - Solution- use video compression algorithms or
codecs - Codecs compress the video for delivery and then
decode it for playback at rates from 501 to 2001
43Video 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 users computer instead of
waiting for the whole file to download - ( RealAudio and RealVideo software)
44MPEG
- Standard developed by the Moving PIcturesExperts
Group for digital representation of moving
pictures and associated audio - http//mpeg.org
45Digital 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
46Digital 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
47Video Recording and Tape Formats
- Composite analog video.
- Component analog video.
- Composite digital.
- Component digital.
- ATSC digital TV.
48Composite 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.
49Component 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.
50Composite 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.
51Component 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.
52ATSC 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.
53Vaughns Law of Multimedia Minimums
- Your goal is to produce multimedia that is
adequate and does its job but doesnt throw you
into bankruptcy. - Experiment with various levels of consumer grade
equipment - Professional sound and video equipment is very
expensive
54Recording 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 gt 900,000 and produces 15 minutes of
video - Composite Digital most common gt110,000
55Shooting and 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
56Shooting and 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
57Shooting and Editing Video
58Shooting and 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
59Shooting and 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...
60Using 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
61Video 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
62Consumer 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
63Making 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
64Video 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
65Editing 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
66P64
- 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.
67Optimizing 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.
68Optimizing 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
69Optimizing 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
70Summary
- Various video standards are NTSC, PAL, SECAM, and
ATSC DTV. - Categories of video standards are composite
analog, component analog, composite digital, and
component digital.