STREAMING MEDIA

Kim Stanton, UNT Tech Talk, 12/5/2007

“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

What is streaming media?

Streaming vs Downloading

Not downloaded to users computer.

User can skip ahead immediately.

Downloaded to users computer.

Can view after download is complete.

Streaming Downloading

Streaming vs Progressive Download

Not downloaded to users computer.

User can skip ahead immediately.

Downloaded to users computer.

File can start playing before download is complete, but can only play the sections that have been downloaded.

Streaming Progressive Download

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.

1.Digitization2.Compression & encoding3.Streaming

Basic Steps

Digitization

Step One:

Digitization

From analog to digital…

Digitization

…use ‘analog to digital’ converter.

Analog signal

Digital signal

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…

ConversionSoftware

ConversionSoftware

Digitization

…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!

Compression & Encoding

Step Two:

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 the Media

Availablebandwidth

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

User picks 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

Server detects user’s connection and chooses appropriate delivery rate.

Encoding Bit Rates

Variable Bit Rate Bit rate 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 “blue” codec.

Media player with “blue” codec key.

Media Players

Codec also determines media player.

File created with “blue” codec.

Media player with “red” codec key.

X

Media Players

Codec also determines media player.

File created with “blue” codec.

Media player with 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.

Streaming

Step Three:

Streaming Server

File is uploaded to streaming server

Streaming Server

Pushed for live feeds

Pulled for on-demand

Live Lecture

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

Per Faculty 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!)