6. Digital VDO
• A means of reproducing the continuous VDO
waveform as a stream of digital numbers.
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• Interlacing was originally conceived as a way to
achieve good visual quality within a limitations
of a narrow bandwidth.
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8. 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.
9. 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)
10. 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. 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. 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. 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. VDO Compression
• Spatial compression (intra-frame)
• Temporal compression (inter-frame)
• Video compression is a tradeoff between disk
space, video quality, and the cost of hardware
required to decompress the video in a
reasonable time.
16. Temporal Compression
• Make key frames, say every 6 frames and do the
spatial compression on these frames.
• Between key frames, each one of them will be
replaced by a difference frame.
19. 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.
20. MOV
• Quicktime Movie was developed by Apple
Computer
• MPEG-4
• Qt 7 (and later) use H.264
21. 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
22. • 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
23. 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
28. Coaxial
• VDO and audio signals are both carries in one
cable
• Poorest transfer
29. A/V
• Use RCA connectors
• Yellow is (composite) video
• Red is right audio & White is left audio
30. 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
33. FireWire
• Developed by Apple
Computer
• IEEE-1394 standard
• 400 Mbps
• higher transfer rates are
available (800, 1600, and
up to 3100 Mbps)
34. 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
35. VDO Editing
• Editing:
• cut and paste sections
• add special effects
• add transitions
• add titles
![ia Systems
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