Streaming media
Overview
 
Streaming media is multimedia
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...

 that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather than to the medium itself. The distinction is usually applied to media that are distributed over telecommunications network
Telecommunications network
A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...

s, as most other delivery systems are either inherently streaming (e.g., radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

, television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

) or inherently non-streaming (e.g., books, video cassettes
Videotape
A videotape is a recording of images and sounds on to magnetic tape as opposed to film stock or random access digital media. Videotapes are also used for storing scientific or medical data, such as the data produced by an electrocardiogram...

, audio CD
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

s).
Encyclopedia
Streaming media is multimedia
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...

 that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather than to the medium itself. The distinction is usually applied to media that are distributed over telecommunications network
Telecommunications network
A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...

s, as most other delivery systems are either inherently streaming (e.g., radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

, television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

) or inherently non-streaming (e.g., books, video cassettes
Videotape
A videotape is a recording of images and sounds on to magnetic tape as opposed to film stock or random access digital media. Videotapes are also used for storing scientific or medical data, such as the data produced by an electrocardiogram...

, audio CD
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

s). The verb 'to stream' is also derived from this term, meaning to deliver media in this manner. Internet television
Internet television
Internet television is the digital distribution of television content via the Internet...

 is a commonly streamed medium.

Live streaming, delivering live over the Internet, involves a camera for the media, an encoder to digitize the content, a media publisher, and a content delivery network
Content Delivery Network
A content delivery network or content distribution network is a system of computers containing copies of data placed at various nodes of a network....

 to distribute and deliver the content.

History

Attempts to display media on computers date back to the earliest days of computing in the mid-20th century. However, little progress was made for several decades, primarily due to the high cost and limited capabilities of computer hardware.

From the late 1980s through the 1990s, consumer-grade personal computers became powerful enough to display various media. The primary technical issues related to streaming were:
  • having enough CPU power and bus bandwidth
    Bandwidth (computing)
    In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...

     to support the required data rates
  • creating low-latency
    Latency (engineering)
    Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured. Latencies may have different meaning in different contexts.-Packet-switched networks:...

     interrupt paths in the operating system
    Operating system
    An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

     (OS) to prevent buffer underrun
    Buffer underrun
    In computing, buffer underrun or buffer underflow is a state occurring when a buffer used to communicate between two devices or processes is fed with data at a lower speed than the data is being read from it. This requires the program or device reading from the buffer to pause its processing while...

    .


However, computer networks were still limited, and media was usually delivered over non-streaming channels, such as by downloading a digital file from a remote server and then saving it to a local drive on the end user's computer or storing it as a digital file and playing it back from CD-ROM
CD-ROM
A CD-ROM is a pre-pressed compact disc that contains data accessible to, but not writable by, a computer for data storage and music playback. The 1985 “Yellow Book” standard developed by Sony and Philips adapted the format to hold any form of binary data....

s.

During the late 1990s and early 2000s, Internet users saw:
  • greater network bandwidth, especially in the last mile
    Last mile
    The "last mile" or "last kilometer" is the final leg of delivering connectivity from a communications provider to a customer. The phrase is therefore often used by the telecommunications and cable television industries. The actual distance of this leg may be considerably more than a mile,...

  • increased access to networks, especially the Internet
    Internet
    The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

  • use of standard protocols and formats, such as TCP/IP
    Internet protocol suite
    The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...

    , HTTP
    Hypertext Transfer Protocol
    The Hypertext Transfer Protocol is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web....

    , and HTML
  • commercialization of the Internet.


Severe Tire Damage
Severe Tire Damage (band)
Severe Tire Damage is a rock and roll "garage" band from Palo Alto, California.-Uniqueness:Severe Tire Damage was the first band to perform live on the Internet...

 was the first band to perform live on the Internet. On June 24, 1993, the band was playing a gig at Xerox PARC while elsewhere in the building, scientists were discussing new technology (the Mbone
Mbone
Mbone was an experimental backbone for IP multicast traffic across the Internet developed in the early 1990s. It required specialized hardware and software...

) for broadcasting on the Internet using multicasting. As proof of their technology, the band was broadcast and could be seen live in Australia and elsewhere.

RealNetworks
RealNetworks
RealNetworks, Inc. is a provider of Internet media delivery software and services based in Downtown Seattle, Washington, United States. The company is the creator of RealAudio, a compressed audio format; RealVideo, a compressed video format; RealPlayer, a media player; RealDownloader, a download...

 were also pioneers in the streaming media markets and broadcast one of the earlier audio events over the Internet - a baseball game between the Yankees and Seattle Mariners - in 1995. They went on to launch the first streaming video technology in 1997.

These advances in computer networking combined with powerful home computers and modern operating systems made streaming media practical and affordable for ordinary consumers. Stand-alone Internet radio device
Internet radio device
An Internet radio device, also called network music player is a hardware device that is capable of receiving and playing streamed media from either Internet radio stations or a home network.-Background:...

s emerged to offer listeners a no-computer option for listening to audio streams.

In general, multimedia content has a large volume, so media storage and transmission costs are still significant. To offset this somewhat, media are generally compressed
Data compression
In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....

 for both storage and streaming.

Increasing consumer demand for streaming of high definition (HD) content to different devices in the home has led the industry to develop a number of technologies, such as Wireless HD or ITU-T
ITU-T
The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....

 G.hn
G.hn
G.hn is the common name for a home network technology family of standards developed under the International Telecommunication Union's Standardization arm and promoted by the HomeGrid Forum...

, which are optimized for streaming HD content without forcing the user to install new networking cables
Networking cables
Networking Cables are used to connect one network device to other or to connect two or more computers to share printer, scanner etc. Different types of network cables like Coaxial cable, Optical fiber cable, Twisted Pair cables are used depending on the network's topology, protocol and size. The...

.

Increasing consumer demand for live streaming has prompted YouTube
YouTube
YouTube is a video-sharing website, created by three former PayPal employees in February 2005, on which users can upload, view and share videos....

 to implement their new Live Streaming service to users.

A media stream can be streamed either live or on demand. Live streams are generally provided by a means called true streaming. True streaming sends the information straight to the computer or device without saving the file to a hard disk. On Demand streaming is provided by a means called progressive streaming or progressive download
Progressive download
Progressive download is a term used to describe the transfer of digital media files from a server to a client, typically using the HTTP protocol when initiated from a computer. The consumer may begin playback of the media before the download is complete...

.
Progressive streaming saves the file to a hard disk and then is played from that location. On Demand streams are often saved to hard disks and servers for extended amounts of time; while the live streams are only available at one time only (e.g. during the Football game).

Streaming bandwidth and storage

A broadband speed of 2.5 Mbit/s or more is recommended for streaming movies, for example to an Apple TV, Google TV
Google TV
Google TV is a Smart TV platform from Google. It was announced on May 20, 2010, at Google’s Google I/O event and was co-developed by Google, Intel, Sony and Logitech...

 or a Sony TV Blu-ray Disc Player, 10 Mbit/s for High Definition content.

Streaming media storage size is calculated from the streaming bandwidth and length of the media using the following formula (for a single user and file):
storage size (in mebibyte
Mebibyte
The mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 220, therefore 1 mebibyte is . The unit symbol for the mebibyte is MiB. The unit was established by the International Electrotechnical Commission in 2000 and has been accepted for use by all major...

s) = length (in seconds) × bit rate
Bit rate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....

 (in bit/s) / (8 × 1024 × 1024)1 mebibyte = 8 × 1024 × 1024 bits.


Real world example:

One hour of video encoded at 300 kbit/s (this is a typical broadband video and it is usually encoded in a 320 × 240 pixels window size) will be:
/ (8×1024×1024) requires around 128 MiB
Mebibyte
The mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 220, therefore 1 mebibyte is . The unit symbol for the mebibyte is MiB. The unit was established by the International Electrotechnical Commission in 2000 and has been accepted for use by all major...

 of storage.

If the file is stored on a server for on-demand streaming and this stream is viewed by 1,000 people at the same time using a Unicast
Unicast
right|200pxIn computer networking, unicast transmission is the sending of messages to a single network destination identified by a unique address.-Addressing methodologies:...

 protocol, the requirement is:
300 kbit/s × 1,000 = 300,000 kbit/s = 300 Mbit/s of bandwidth


This is equivalent to around 135 GB
Gigabyte
The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units , therefore 1 gigabyte is...

 per hour. Using a multicast
Multicast
In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...

 protocol the server sends out only a single stream that is common to all users. Hence, such a stream would only use 300 kbit/s of serving bandwidth. See below for more information on these protocols.

The calculation for Live streaming is similar.

Assumptions: speed at the encoder, is 500 kbit/s.

If the show lasts for 3 hours with 3,000 viewers, then the calculation is:
Number of MiB transferred = encoder speed (in bit/s) × number of seconds × number of viewers / (8*1024*1024)

Number of MiB transferred = 500,000 (bit/s) × 3 × 3,600 ( = 3 hours) × 3,000 (nbr of viewers) / (8*1024*1024) = 1,931,190 MiB

Codec, bitstream, transport, control

The audio stream is compressed using an audio codec such as MP3, Vorbis or AAC.

The video stream is compressed using a video codec such as H.264 or VP8.

Encoded audio and video streams are assembled in a container bitstream such as FLV, WebM, ASF or ISMA.

The bitstream is delivered from a streaming server to a streaming client using a transport protocol, such as MMS or RTP
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...

.

The streaming client may interact with the streaming server using a control protocol, such as MMS or RTSP.

Protocol issues

Designing a network protocol to support streaming media raises many issues, such as:
  • Datagram
    Datagram
    A datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....

     protocols, such as the User Datagram Protocol
    User Datagram Protocol
    The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...

     (UDP), send the media stream as a series of small packets. This is simple and efficient; however, there is no mechanism within the protocol to guarantee delivery. It is up to the receiving application to detect loss or corruption and recover data using error correction techniques. If data is lost, the stream may suffer a dropout
    Dropout (electronics)
    Dropout within the realm of electronics and electrical engineering, has a number of uses.It is the dropping away of a flake of magnetic material from magnetic tape, leading to loss of signal, or a failure to properly read a binary character from data storage...

    .
  • The Real-time Streaming Protocol (RTSP), Real-time Transport Protocol
    Real-time Transport Protocol
    The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...

     (RTP) and the Real-time Transport Control Protocol (RTCP) were specifically designed to stream media over networks. RTSP runs over a variety of transport protocols, while the latter two are built on top of UDP.
  • Another approach that seems to incorporate both the advantages of using a standard web protocol and the ability to be used for streaming even live content is the HTTP adaptive bitrate streaming. HTTP adaptive bitrate streaming is based on HTTP progressive download, but contrary to the previous approach, here the files are very small, so that they can be compared to the streaming of packets, much like the case of using RTSP and RTP.
  • Reliable protocols, such as the Transmission Control Protocol
    Transmission Control Protocol
    The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...

     (TCP), guarantee correct delivery of each bit in the media stream. However, they accomplish this with a system of timeouts and retries, which makes them more complex to implement. It also means that when there is data loss on the network, the media stream stalls while the protocol handlers detect the loss and retransmit the missing data. Clients can minimize this effect by buffering data for display. While delay due to buffering is acceptable in video on demand scenarios, users of interactive applications such as video conferencing will experience a loss of fidelity if the delay that buffering contributes to exceeds 200 ms.
  • Unicast
    Unicast
    right|200pxIn computer networking, unicast transmission is the sending of messages to a single network destination identified by a unique address.-Addressing methodologies:...

     protocols send a separate copy of the media stream from the server to each recipient. Unicast is the norm for most Internet connections, but does not scale well when many users want to view the same television program
    Television program
    A television program , also called television show, is a segment of content which is intended to be broadcast on television. It may be a one-time production or part of a periodically recurring series...

     concurrently.

  • Multicast
    Multicast
    In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...

     protocols were developed to reduce the data replication (and consequent server/network loads) that occurs when many recipients receive unicast content streams independently. These protocols send a single stream from the source to a group of recipients. Depending on the network infrastructure and type, multicast transmission may or may not be feasible. One potential disadvantage of multicasting is the loss of video on demand
    Video on demand
    Video on Demand or Audio and Video On Demand are systems which allow users to select and watch/listen to video or audio content on demand...

     functionality. Continuous streaming of radio or television material usually precludes the recipient's ability to control playback. However, this problem can be mitigated by elements such as caching servers, digital set-top box
    Set-top box
    A set-top box or set-top unit is an information appliance device that generally contains a tuner and connects to a television set and an external source of signal, turning the signal into content which is then displayed on the television screen or other display device.-History:Before the...

    es, and buffered media players.
  • IP Multicast
    IP Multicast
    IP multicast is a method of sending Internet Protocol datagrams to a group of interested receivers in a single transmission. It is often employed for streaming media applications on the Internet and private networks. The method is the IP-specific version of the general concept of multicast...

     provides a means to send a single media stream to a group of recipients on a computer network
    Computer network
    A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

    . A multicast protocol, usually Internet Group Management Protocol
    Internet Group Management Protocol
    The Internet Group Management Protocol is a communications protocol used by hosts and adjacent routers on IP networks to establish multicast group memberships....

    , is used to manage delivery of multicast streams to the groups of recipients on a LAN. One of the challenges in deploying IP multicast is that routers and firewalls between LANs must allow the passage of packets destined to multicast groups. If the organization that is serving the content has control over the network between server and recipients (i.e., educational, government, and corporate intranet
    Intranet
    An intranet is a computer network that uses Internet Protocol technology to securely share any part of an organization's information or network operating system within that organization. The term is used in contrast to internet, a network between organizations, and instead refers to a network...

    s), then routing protocols such as Protocol Independent Multicast
    Protocol Independent Multicast
    Protocol-Independent Multicast is a family of multicast routing protocols for Internet Protocol networks that provide one-to-many and many-to-many distribution of data over a LAN, WAN or the Internet...

     can be used to deliver stream content to multiple Local Area Network
    Local area network
    A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...

     segments.
  • Peer-to-peer
    Peer-to-peer
    Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...

     (P2P) protocols arrange for prerecorded streams to be sent between computers. This prevents the server and its network connections from becoming a bottleneck. However, it raises technical, performance, quality, and business issues.

See also

  • Comparison of streaming media systems
    Comparison of streaming media systems
    This is a comparison of streaming media systems. A more complete list of streaming media systems is also available.-General:The following tables compare general and technical information for a number of streaming media systems both audio and video...

  • Comparison of video services
    Comparison of video services
    The following tables compare general and technical information for a number of notable video hosting services. Please see the individual products' articles for further information...

  • Content delivery platform
    Content Delivery Platform
    A content delivery platform is a software as a service content service, similar to a content management system , that utilizes embedded software code to deliver web content...

  • Destreaming
  • Digital television
    Digital television
    Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...

  • Grid casting
    Grid casting
    Grid casting or gridcasting is a file and stream sharing system that cooperates transparently by using idle bandwidth on a user's computer to deliver large scale live or on-demand broadcasts...

  • HTTP Live Streaming
    HTTP Live Streaming
    HTTP Live Streaming is an HTTP-based media streaming communications protocol implemented by Apple Inc. as part of their QuickTime X and iPhone software systems. It works by breaking the overall stream into a sequence of small HTTP-based file downloads, each download loading one short chunk of an...

  • HTTP(P2P)
    HTTP(P2P)
    HTTP is a protocol based on HTTP. It is intended to improve page and object retrieval performance when web servers suffer server-side congestion. Examples of server-side congestion include the Slashdot and Flash crowd effects...

  • IPTV
    IPTV
    Internet Protocol television is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats.IPTV services...

  • List of music streaming services
  • List of streaming media systems
  • Multicast
    Multicast
    In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...

  • P2PTV
    P2PTV
    The term P2PTV refers to peer-to-peer software applications designed to redistribute video streams in real time on a P2P network; the distributed video streams are typically TV channels from all over the world but may also come from other sources...

  • Protection of Broadcasts and Broadcasting Organizations Treaty
    Protection of Broadcasts and Broadcasting Organizations Treaty
    The WIPO Protection of Broadcasts and Broadcasting Organizations Treaty or the Broadcast Treaty is a treaty designed to afford broadcasters some control and copyright-like control over the content of their broadcasts...

  • Push technology
    Push technology
    Push technology, or server push, describes a style of Internet-based communication where the request for a given transaction is initiated by the publisher or central server...

  • Stream processing
    Stream processing
    Stream processing is a computer programming paradigm, related to SIMD , that allows some applications to more easily exploit a limited form of parallel processing...

  • Webcast
    Webcast
    A webcast is a media presentation distributed over the Internet using streaming media technology to distribute a single content source to many simultaneous listeners/viewers. A webcast may either be distributed live or on demand...

  • Web syndication
    Web syndication
    Web syndication is a form of syndication in which website material is made available to multiple other sites. Most commonly, web syndication refers to making web feeds available from a site in order to provide other people with a summary or update of the website's recently added content...

  • Web television
    Web television
    Web television, also commonly referred to as web TV, not to be confused with WebTV, Internet television or catch up TV, is an emerging genre of digital entertainment that is distinct from traditional broadcast television...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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