STREAMING MEDIA Kim Stanton UNT Tech Talk 12 5 2007

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

Streaming vs Progressive Download Streaming Not downloaded to users computer. User can skip ahead immediately. Progressive Downloaded to users computer. File can start playing before 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. 2. 3. Digitization Compression & encoding Streaming

Step One: Digitization

Digitization From analog to digital…

Digitization Analog signal Digital signal …use ‘analog to digital’ converter.

Digitization Why? VHS, 16 mm, 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 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 56 kbit/s dial up modem.

Bandwidth File compressed for a T 1 connection won’t stream at an appropriate, consistent rate.

Bandwidth But a file compressed for a 56 kbit/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: 56 kbit/s or 120 kbit/s or 1 MBit/s , etc User picks rate (if given option) Default

Encoding Bit Rates Multiple Bit Rate Several delivery rates encoded in one file. 56 kbit/s and 180 kbit/s and 1. 5 Mbit/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 H. 264 to MPEG-1 & 2 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 (Hi. P)

Proprietary Standards Apple Quicktime Real. Networks Windows Media Flash Div. X

Open source standards Xvid Uses MPEG-4, part 2 Open. AVS 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. X File created with “blue” codec. Media player with “red” codec key.

Media Players Codec also determines media player. File created with “blue” codec. Media player with multiple codec keys.

Media Players The Big (proprietary) Four Real. Media Player Real. Networks 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 send packets of information to users.

Streaming 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: Real. Networks 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? /d. Online+media. Collection Broad, Development high use, educational materials Distributers offering digital licensing

@UNT streaming server: Managed by CITC Real. Networks Live stream and On-demand http: //media. unt. edu: 8080… Examples: Texas Center for Digital Knowledge Peer Forums Course related media (CDL/ Web. CT)

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 http: //www. nfb. ca/duneculturealautre/toutvoir. php Open Film Board of Canada Vault, WGBH http: //openvault. wgbh. org/

Free Online Media User Generated Content Usually progressive download You. Tube Google Video Internet Archive Metacafe Vimeo Blip. tv Yahoo Video Dance. Jam (coming soon!)