22. Digital VDO
• A means of reproducing the continuous
VDO waveform as a stream of digital numbers.
6
23. Digital VDO
• A means of reproducing the continuous
VDO waveform as a stream of digital numbers.
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6
24. Interlacing
open wiki to
embrace the
explanation!!
• Interlacing was originally conceived as a way
to achieve good visual quality within a
limitations of a narrow bandwidth.
even field
odd field
7
25. Progressive Scanning
(non-interlaced scanning)
• A method of representing
moving images on a display
screen, in which every pixel is
represented in each frame.
• Computer monitors use a progressive scan.
• The standard refresh rate for a flicker-free
display is a vertical scan rate of 75 Hz or
higher.
• It’s used to project movies in theaters.
8
26. Note
in digital TV terminology:
interlaced scan is denoted
by a lowercase i
progressive scan is
denoted by a lowercase p
frame rate: (60i, 24p)
resolution: (1080i, 720p)
9
27. Flicker Rate
• Flicker fusion rate is the human eye’s ability
to notice flicker within rapid pulses of light.
• Flicker will be observed if a light pulses on
and off below 72 pulses per second (pps).
10
28. Frame Rate
• Frame frequency is a measure of how
quickly an image device can produce
unique consecutive images called
frames. (expressed in frames per second - fps)
• Typically, the human eye can interpret motion at
10 fps, but this rate causes a flicker effect that’s
distract.
• Increasing the frame rate reduces flickering.
11
29. Frame Rate
• Movies - 14 fps
• Television:
• NTSC - 29.97 fps
• HDTV - 60 fps
• VDO games (frame rate is very important):
• action-oriented games - 20-30 fps
• 3D-heavy games - 90-100 fps
12
30. Aspect Ratios
• The ratio of the width of the image to its
height (w:h)
• motion-picture - 1.85:1 and 2.35:1
• tv screens - 1.33:1 (aka 4:3)
• HDTV - 1.78:1 (aka 16:9)
16:9 4:3 letterbox
13
31. Compression
• VDO is huge - one sec of analog VDO
stored in an uncompressed digital format
takes up 1 MB of disk space
• thus, 5-min VDO ~ 300 MB
• not practical
• VDO compression is a MUST
• VDO contains many spatial and temporal
redundancies
• Codecs are needed for creating and
viewing
14
33. AVI
• Most common AV data on Windows
• Can be saved in a variety of compression
schemes - full frames (uncompressed),
Radius’s Cinepak, Intel Video, and Indeo.
16
35. MPG
• The compressed VDO file format for
standard DVD using the MPEG-2 encoding
standard
• A large file can be transferred to MPEG with
little loss of quality while dropping the bit
rate a great deal
18
36. • The MPEG group develops the standards for
encoding VDO and audio
• MPEG standards:
• MPEG-1: used as VCD standard (MP3 is
the popular compression)
• MPEG-2: use in many things such as DVD,
digital satellite TV and so on
• MPEG-4: support 3D content, low bit-rate
encoding, support for Digital Right
Management
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37. Others
• WMV
• a part of Windows Media framework
• used for streaming VDO over the internet
• uses MPEG-4 standard
• RM
• a multimedia container with RealVideo
and RealAudio codecs in a single file
• is used to stream AV over the internet
20
41. Coaxial
• VDO and audio signals are both carries in
one cable
• Poorest transfer
24
42. A/V
• Use RCA connectors
• Yellow is (composite) video
• Red is right audio & White is left audio
25
43. S-Video
• Separate video - transmit
VDO signals over a cable by
dividing the VDO info into 2
separate signals: color
(chrominance) and brightness
(luminance)
• Sharper than composite VDO
• must be used in conjunction
with audio cables
26
45. FireWire
• Developed by Apple
Computer
• IEEE-1394 standard
• 400 Mbps
• higher transfer rates
are available (800,
1600, and up to 3100
Mbps)
28
46. Transferring from
Recorder to Computer
• Calculate disk space (uncompressed):
• (pixel width) x (pixel height) x (color bit
depth) x (fps) x (duration in secs) /
8,000,000
• say, 3-min VDO @ 15 fps, 24-bit depth,
320x240 pixels will take:
• (320) x (240) x (24) x (15) x (180) /
8,000,000 = 622 MB
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