STREAMING MEDIA
Kim Stanton, UNT Tech Talk, 12/5/2007
What is streaming media?
“Media content that is delivered to the
viewer’s media player in real-time”
“There is not intermediated storage of
the content…the data is processed as
it arrives..and then discarded.”
David Austerberry
Technology of Video &
Audio Streaming
Two types of streaming:
On Demand streaming
Live streaming, aka “webcasting”
Similar to television?
On Demand cable movies
Live broadcasts
Streaming vs Downloading
Streaming Downloading
Not downloaded to Downloaded to
users computer. users computer.
User can skip Can view after
ahead download is
immediately. complete.
Streaming vs
Progressive Download
Streaming Progressive Download
Not downloaded to Downloaded to
users computer. users computer.
User can skip File can start
ahead playing before
immediately. download is
complete, but can
only play the
sections that have
been downloaded.
When to choose streaming:
Security of content
Considered safer for content owners.
For live events
Events can be streamed as they are
happening.
Live speakers, sporting events
For quick access
Don’t have to wait for a complete download
Progressive download offers similar workarounds.
Basic Steps
1. Digitization
2. Compression & encoding
3. Streaming
Step One:
Digitization
Digitization
From analog to digital…
Digitization
Analog Digital
signal signal
…use ‘analog to digital’ converter.
Digitization
Why?
VHS, 16mm, audio cassette players, etc
send out analog signals.
Computers accept digital signals.
Analog-to-Digital converters
External – AV conversion box
Internal – video capture card
Digitization
From digital to “malleable” digital…
Digitization
Conversion
Software
…use conversion/ripping software.
Digitization
Why?
Conversion software makes a malleable
copy of the digital file.
Digitization
Why?
Conversion software makes a malleable
copy of the digital file.
Follow copyright law!
Step Two:
Compression &
Encoding
Software
Compression and encoding done by
authoring software on computer.
Sorenson Squeeze (what ML uses)
Windows Movie Maker
Real Producer
Quicktime
Adobe Flex
Other third party authoring software
Compression
Compression:
reduces the file size by removing specific
bits of data that represent the audio and
video.
All streaming media compression is “lossy”.
Lossless compression does not provide a
small enough file to stream.
Types of compression
Intraframe compression
Similar to still image compression
“Motion JPEG Compression”
Frames are considered individually
Process repeats for each frame of movie
Interframe compression
Considers frames in adjacent groups
Repeating data is discarded
Similar to older animation.
Compression
Why compress?
To reduce the file size:
To deliver stream to the user
To conserve storage space
Choosing a compression rate is a balance:
Quality of Available
the Media bandwidth
Bandwidth
Match the user’s connection
Affects “real time” viewing quality
Less important with downloading
Media not viewed until download is complete.
Doesn’t affect real time viewing speed
Bandwidth
User has a 56kbit/s dial up modem.
Bandwidth
File compressed for a T1 connection won’t
stream at an appropriate, consistent rate.
Bandwidth
But a file compressed for a 56kbit/s connection will.
Bandwidth
A file compressed at a higher rate will stream
correctly at a higher connection speed.
Encoding Bit Rates
Three methods of encoding bit rate
Constant Bit Rate
Multiple Bit Rate
Variable Bit Rate
Encoding Bit Rates
Constant Bit Rate:
A single delivery rate:
56kbit/s or 120kbit/s or 1MBit/s , etc
Userpicks rate (if given option)
Default
Encoding Bit Rates
Multiple Bit Rate
Several delivery rates encoded in one file.
56kbit/s and 180kbit/s and 1.5Mbit/s
detects user’s connection and
Server
chooses appropriate delivery rate.
Encoding Bit Rates
Variable Bit Rate
Bitrate adjusts during the duration of the
movie, depending on the “action” level.
Done with multi-pass encoding
Pass 1: Monitors action levels
Pass 2: Encodes
Encoding
Compression & encoding specifications
are done with compression codecs.
Compression codecs
International standards
Proprietary formats
Open standards
International standards
MPEG-4
Update to MPEG-1 & 2
H.264 or AVC (Advanced Video Codec)
High quality at small bit rate
Different levels
Handheld devices– base profile (BP)
Streaming - Extended profile(XP)
HD – High Profile (HiP)
Proprietary Standards
Apple Quicktime
RealNetworks
Windows Media
Flash
DivX
Open source standards
Xvid
Uses MPEG-4, part 2
OpenAVS
Similar to H.264 codec
Dirac
For European PAL television signal
Media Players
Codec also determines media player.
File created with Media player with
“blue” codec. “blue” codec key.
Media Players
Codec also determines media player.
X
File created with Media player with
“blue” codec. “red” codec key.
Media Players
Codec also determines media player.
File created with Media player with
“blue” codec. multiple codec keys.
Media Players
The Big (proprietary) Four
RealMedia Player
RealNetworks
Windows Media Player
Microsoft
Quicktime
Apple
Flash
Adobe
Lots of other players out there.
Step Three:
Streaming
Streaming Server
File is uploaded to streaming server
Streaming Server
Pushed for live feeds
Live Lecture
Pulled for on-demand
Film for class
Streaming Server
Server send packets of information to
users.
Streaming Server
Server send packets of information to
users.
Media is played then discarded.
Examples
@ UNT Media Library
Streaming Media Interface
https://libhelix.library.unt.edu/login.cfm
Specifications:
RealNetworks Helix streaming server
.rm files & Real Media Player
Multiple bit rate encoding
@ UNT Media Library
Streaming Media Interface
https://libhelix.library.unt.edu/login.cfm
On Demand Access
Two access levels:
Limited to course enrollment
All Active Eagles
@ UNT Media Library
Limited to course enrollment
Open to only faculty and students enrolled
in a specific course
Why? Licensing agreements
Authenticates through LDAP
Collection development
PerFaculty requests
Media used in face to face courses.
@ UNT Media Library
All Active Eagles
All current UNT students, faculty, staff.
Currently, 7 films available
50+ PBS titles in process
Titles searchable in library catalog
http://iii.library.unt.edu/search?/dOnline+media.
Collection Development
Broad, high use, educational materials
Distributers offering digital licensing
@UNT
UNT streaming server:
Managed by CITC
RealNetworks
Live stream and On-demand
http://media.unt.edu:8080…
Examples:
Texas Center for Digital Knowledge
Peer Forums
Course related media (CDL/ WebCT)
Free Online Media
Streaming examples
Annenberg
http://www.learner.org/
Internet Archive, Moving Image Archive
http://www.archive.org/details/movies
Stream and/or download
American Field Guide
http://www.pbs.org/americanfieldguide/index.html
Free Online Media
Progressive Download examples
Frontline
http://www.pbs.org/wgbh/pages/frontline/
National Film Board of Canada
http://www.nfb.ca/duneculturealautre/toutvoir.php
Open Vault, WGBH
http://openvault.wgbh.org/
Free Online Media
User Generated Content
Usually progressive download
YouTube
Google Video
Internet Archive
Metacafe
Vimeo
Blip.tv
Yahoo Video
DanceJam (coming soon!)