Streaming Media - Background

Streaming Protocols

Significant Technological Breakthroughs

• adoption of the User Datagram Protocol (UDP) and - more recently - RealTime Streaming protocol (RTSP)
  • made streaming media possible due to more efficient data transmission
• new encoding techniques (perceptual encoding alogrithms) that succeeded in compressing audio files into much smaller packets of data
• continuing improvement in user connection speeds

UDP & RTSP

These more recent protocols are deal for broadcasting, because they place the highest priority on sending a continuous stream of data, rather than document security

• When an audio packet drops out using TCP (Transmission Control Protocol) or HTTP (HyperText Transfer Protocol), the server keeps trying to resend the lost packet before sending additional packets
  • designed to reliably transfer text documents, email, and HTML web pages, enforcing maximum reliability and data integrity
  • since HTTP is based on TCP, it is not particularly well-suited for transmitting multimedia presentations that rely on time-based operations or for large-scale broadcasting
• In contrast, when using UDP or RTSP, the server keeps sending information, causing only a brief glitch in the sound file rather than a gap of silence.

File Formats

• RealMedia, QuickTime, and Windows Media utilize dedicated servers that support the superior transmission protocols (UDP & RTSP)
• Other formats (Shockwave, Flash, MIDI, Beatnik, etc.) are primarily designed to run from a standard HTTP server (e.g., the FastStart QuickTime movie)
  • like RealMedia, with the arrival of the QuickTime Server, it is now possible to stream Quicktime files either from RTSP or HTTP servers
  • HTTP streaming is often referred to as pseudo-streaming (this is what Apple calls "Fast Start" when using QuickTime) ... it is technically possible, but
    • more likely to cause major packet drop-outs
    • cannot deliver near as many streams of data as UDP & RT

Currently, RealPlayer, QuickTime Player, and Windows Media Player are all supporting multiple sound file formats ... and attempting to gain a larger audience share by supporting one another's file formats.

Compression Types

• "lossy" compression schemes reduce file size by discarding some amount of data during the encoding process ("perceptual coding"). Lossy compression offers file size reduction of approximately 10:1
  • graphic - JPEG
  • audio - MP3, RealMedia, Quicktime, and most audio compression algorithms
• "lossless" compression places data into smaller packets of information without permanently discarding any data. When using a lossless compression scheme, data is discarded temporarily - hence, the reduction in file size - but provides a "map" with which the file can be reconstructed using a "codec" (COmpression-DECompression algorithm) ... though resulting in a superior audio quality, the file size reduction is less
  • graphic - GIF

Server Requirements & Cost - [detailed comparison of audio formats]

QuickTime (best performance with Mac OS X Server)

• leading video production platform for both Windows and Macintosh (Beggs & Thede, 2001)
• support for an increased number of formats (MP3, Flash, MIDI, and almost every audio, video, image, animation, 3-D, and virtual reality format available
• the initial download of QuickTime is now smaller, since it includes fewer codecs; additional codecs are downloaded (in the background) as required
• allows true RTSP streaming (in addition to HTTP) when used in conjunction with Mac OS X Server

RealMedia (best with RealServer)

• most widely adopted streaming media format on the web, according to NetMedia magazine (April 2001, p. 20):
  • every week, more than 350,000 hours of live sports, news, music, business communications, and entertainment are streamed over the internet using RealSystem technology
  • RealSystem software is used to deliver content on more than 85% of all websites with streaming media
• broadcasting audio with a dedicated REalServer provides numerous advantages over HTTP:
  • SureStream technology allows creation of a single file that will stream to any given user at the best audio quality available at their connection speed
  • RTSP transmission detects & compensates for lost packets, maintaining smooth, continuous playback ... something HTTP streaming cannot do
  • signal can be split and routed to different RealServers at various locations on the internet
  • RealServers can be clustered together so they work as a single, integrated, multi-processor machine
  • multicasting allows all users of a network to listen to a single live stream, making efficient use of network resources

Windows Media Player with Windows NT/2000

• comes free with unlimited streams with Windows NT Server 4.0 or later
• includes Windows T.A.G. Author, a tool for creating multimedia content developers that allows synchronization of audio & video
• better playback over Windows-based computers ... hmmmm
• allows pay-per-view or pay-per-minute billing capabilities using Microsoft Site Server
  • also has significant tools for tracking behavior
• Drawbacks
  • runs only on Windows NT/2000
  • does not support Flash or SMIL

Flash

• vector animation
• soundtracks encoded in MP3 format
• can be streamed via RealServer

Shockwave

• capable of extremely complex interactive web presentations
• incorporates a powerful scripting language (Lingo)

Beatnik's Rich Music Format (RMF)

• HTML-based format utilizes common scripting languages (e.g., JavaScript) to synchronize audio (MIDI & short digital samples) with web content
• Since it uses primarily MIDI, file size is extremely small
• Drawback
  • steep learning curve
  • relies on the Beatnik plug-in (not as ubiquitous as RealPlayer or QuickTime)
  • user must learn JavaScript to control audio playback and synchronization

MP3

• great sound quality with excellent compression (often more than 10:1)
• widespread industry support ... not including record companies
• compatible with many applications & media players

Liquid Audio

• complete end-to-end solution for secure music delivery over the Internet, providing a professional utility for music sales & distribution
• consists of four core products:
  • Liquifier Pro - encoder with powerful watermarking & anti-piracy protections
  • Liquid Server - lets you publish and host Liquid Audio tracks
  • Liquid Player - allows you to preview & purchase CD-quality Liquid tracks for playback on Mac or PC
  • Liquid Express - capable of secure real-time preview, approval, delivery, and archiving of broadcast-quality audio

MIDI

• not a streaming format, but frequently used
  • small file size allows quick downloads
  • widely used
• Drawback
  • playback can vary significantly in quality and instrument playback style

Selecting the Right Format

• Factors in the decision-making process:
  • audio quality & compression, especially low bandwidth performance
  • continuous playback vs. interactive sound design capabilities
  • browser & platform compatibility
  • cost [encoder price comparision]
    • dedicated server, software, hardware, bandwidth, etc.
    • if relevant, server performance & software quality
  • learning curve, documentation, and support