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?

Two types of streaming:  On Demand streaming  Live streaming, aka “webcasting”  Similar to television?  On Demand cable movies  Live broadcasts

Streaming vs Downloading  Not downloaded to users computer.  User can skip ahead immediately.  Downloaded to users computer.  Can view after download is complete. StreamingDownloading

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. StreamingProgressive 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. Digitization 2. Compression & encoding 3. 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…

Conversion Software Conversion Software 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 Available 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  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   Specifications:  RealNetworks Helix streaming server .rm files & Real Media Player  Multiple bit rate encoding

@ UNT Media Library  Streaming Media Interface   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  Collection Development Broad, high use, educational materials Distributers offering digital licensing

@UNT  UNT streaming server:  Managed by CITC  RealNetworks  Live stream and On-demand   Examples: Texas Center for Digital Knowledge Peer Forums Course related media (CDL/ WebCT)

Free Online Media Streaming examples  Annenberg  Internet Archive, Moving Image Archive Stream and/or download  American Field Guide

Free Online Media Progressive Download examples  Frontline  National Film Board of Canada  Open Vault, WGBH

Free Online Media  User Generated Content  Usually progressive download YouTube Google Video Internet Archive Metacafe Vimeo Blip.tv Yahoo Video DanceJam (coming soon!)