Streaming media are 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 only use traditional forms of printed or hand-produced material. Multimedia includes a combination of text, audio, that are constantly received by, and normally presented to, an end-user The end-user is a concept in software engineering, referring to an abstraction of the group of persons who will ultimately operate a piece of software 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 networks 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 can be routed to the correct recipients. The, as most other delivery systems are either inherently streaming (e.g., radio Radio is the transmission of signals 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. Information is carried by systematically changing some property of the radiated waves, such as, television Television is a widely used telecommunication medium for transmitting and receiving moving images, either monochromatic ("black and white") or color, usually accompanied by sound. "Television" may also refer specifically to a television set, television programming or television transmission. The word is derived from mixed Latin) or inherently non-streaming (e.g., books A book is a set or collection of written, printed, illustrated, or blank sheets, made of paper, parchment, or other various material, usually fastened together to hinge at one side. A single sheet within a book is called a leaf, and each side of a leaf is called a page. A book produced in electronic format is known as an electronic book, video cassettes Videotape is a means of recording images and sound on to magnetic tape as opposed to movie film or random access digital media. Videotapes are also used for storing scientific or medical data, such as the data produced by an electrocardiogram. In most cases, a helical scan video head rotates against the moving tape to record the data in two, audio CDs A Compact Disc is an optical disc used to store digital data. It was originally developed to store sound recordings exclusively, but later it also allowed the preservation of other types of data. Audio CDs have been commercially available since October 1982. In 2010, they remain the standard physical storage medium for audio). The verb 'to stream' is also derived from this term, meaning to deliver media in this manner. Internet television Internet television is television service distributed via the Internet. It has become very popular during the 21st century with services such as Hulu and Revision 3 in the United States, Nederland 24 in the Netherlands, ABC iView in Australia, and SeeSaw, BBC iPlayer, 4od, ITV Player and Demand Five in the United Kingdom is a commonly streamed medium.

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 The Central Processing Unit or the processor is the portion of a computer system that carries out the instructions of a computer program, and is the primary element carrying out the computer's functions. This term has been in use in the computer industry at least since the early 1960s . The form, design and implementation of CPUs have changed power and bus bandwidth In computer networking and computer science, bandwidth, digital bandwidth, or network bandwidth is a measure of available or consumed data communication resources expressed in bit/s or multiples of it to support the required data rates
• creating low-latency Low latency allows human-unnoticeable delays between an input being processed and the corresponding output providing real time characteristics. This can be especially important for internet connections utilizing services such as online gaming and VOIP; VOIP is not as important as a minor delay between input from each side of the conversation is interrupt paths in the operating system An operating system is the software on a computer that manages the way different programs use its hardware, and regulates the ways that a user controls the computer. Operating systems are found on almost any device that contains a computer with multiple programs—from cellular phones and video game consoles to supercomputers and web servers. Some (OS) to prevent 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 the buffer refills. This can cause undesired and.

However, computer networks were still limited, and media was usually delivered over non-streaming channels, such as by downloading In computer networks, to download means to receive data to a local system from a remote system, or to initiate such a data transfer. Examples of a remote system from which a download might be performed include a webserver, FTP server, email server, or other similar systems. A download can mean either any file that is offered for downloading or a digital file from a remote web 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-ROMs 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.

During the late 1990s and early 2000s, Internet users saw:

• greater network bandwidth, especially in the last mile The "last mile" or "last kilometre" 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, especially in rural areas. It is
• increased access to networks, especially the Internet The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and
• use of standard protocols and formats, such as TCP/IP The Internet Protocol Suite is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two networking protocols defined in this standard. Today's IP networking, HTTP The Hypertext Transfer Protocol is an Application Layer protocol for distributed, collaborative, hypermedia information systems, and HTML HTML, which stands for HyperText Markup Language, is the predominant markup language for web pages. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists etc as well as for links, quotes, and other items. It allows images and objects to be embedded and can be used to create
• commercialization of the Internet.

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 devices offer listeners a "no-computer" option for listening to audio streams.

In general, 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 only use traditional forms of printed or hand-produced material. Multimedia includes a combination of text, audio, content has a large volume, so media storage and transmission costs are still significant; to offset this somewhat, media are generally compressed In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits than an unencoded representation would use, through use of specific encoding schemes for both storage and streaming.

Increasing consumer demand for streaming of high definition (HD) High-definition television refers to video having resolution substantially higher than traditional television systems (standard-definition TV, or SDTV, or SD). HD has one or two million pixels per frame, roughly five times that of SD. Early HDTV broadcasting used analog techniques, but today HDTV is digitally broadcast using video compression content to different devices in the home has led the industry to develop a number of technologies, such as Wireless HD WirelessHD is an industry-led effort to define a specification for the next generation wireless digital network interface for wireless high-definition signal transmission for consumer electronics products. The consortium currently has over 40 adopters. Key members behind the specification. including Broadcom, Intel, LG, Panasonic, NEC, Samsung, or ITU-T The Telecommunication Standardization Sector coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland G.hn G.hn is the common name for a home network technology standard being developed under the International Telecommunication Union and promoted by the HomeGrid Forum and several other organizations. and several other organizations. It supports networking over power lines, phone lines and coaxial cables with data rates up to 1 Gbit/s, which are optimized for streaming HD content without forcing the user to install new networking cables.

Increasing consumer demand for live streaming has prompted YouTube to implement their new Live Streaming service to users. In 2008 Steve Chen reported to Sarah Meyers of ‘Pop17’ that "Live video is just something that we've always wanted to do, we've never had the resources to do it correctly, but now with Google, we hope to actually do it this year." ^[1]

A media stream can be streamed either by 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. 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).^[2]

Streaming bandwidth and storage

Streaming media storage size (in the common file system measurements mebibytes The mebibyte is a multiple of the unit byte for quantities of digital information. The binary prefix mebi means 220, therefore 1 mebibyte is 1048576bytes. 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 standards organizations. It, megabytes The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: 1048576 bytes generally for computer memory; and one million bytes (106, see prefix mega-) generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000 000", with, gigabytes The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units (SI), therefore 1 gigabyte is 1000000000bytes. The unit symbol for the gigabyte is GB or Gbyte, but not Gb (lower case b) which is typically used for the gigabit, terabytes A terabyte is a SI-multiple (see prefix tera) of the unit byte for digital information storage and is equal to 1012 (1 trillion short scale) bytes. The unit symbol for the terabyte is TB, and so on) is calculated from the streaming bandwidth and length of the media using the following formula (for a single user and file):

storage size (in megabytes) = length (in seconds The second , sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time. It may be measured using a clock) × bit rate In telecommunications and computing, bitrate is the number of bits that are conveyed or processed per unit of time (in bit/s) / (8 × 1024 × 1024)

since 1 mebibyte The mebibyte is a multiple of the unit byte for quantities of digital information. The binary prefix mebi means 220, therefore 1 mebibyte is 1048576bytes. 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 standards organizations. It = 8 × 1024 × 1024 bits.

Real world example:

One hour The hour is a unit of time. It is not an SI unit but is accepted for use with the SI with the symbol h of video encoded at 300 kbit/s (this is a typical broadband video in 2005 and it is usually encoded in a 320×240 pixels window size) will be:

(3,600 s × 300,000 bit/s) / (8×1024×1024) give around 128 MiB The mebibyte is a multiple of the unit byte for quantities of digital information. The binary prefix mebi means 220, therefore 1 mebibyte is 1048576bytes. 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 standards organizations. It 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 In computer networking, unicast transmission is the sending of messages to a single network destination host on a packet switching network protocol, the requirement is:

300 kbit/s × 1,000 = 300,000 kbit/s = 300 Mbit/s In telecommunications, bit rate or data transfer rate is the average number of bits, characters, or blocks per unit time passing between equipment in a data transmission system. This is typically measured in multiples of the units bit per second or byte per second of bandwidth

This is equivalent to around 135 GB The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units (SI), therefore 1 gigabyte is 1000000000bytes. The unit symbol for the gigabyte is GB or Gbyte, but not Gb (lower case b) which is typically used for the gigabit per hour. Of course, using a multicast Multicast addressing is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split 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 In telecommunications, bit rate or data transfer rate is the average number of bits, characters, or blocks per unit time passing between equipment in a data transmission system. This is typically measured in multiples of the units bit per second or byte per second of serving bandwidth. See below for more information on these protocols.

Protocol issues

Designing a network protocol to support streaming media raises many issues, such as:

• 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. A datagram consists of header and data areas, where the header contains information sufficient for routing from the originating equipment to the destination without relying on prior exchanges between the protocols, such as the 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 (IP) network without requiring prior communications to set up special transmission (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 In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels. Many communication channels are subject to channel noise, and thus errors may be introduced during techniques. If data is lost, the stream may suffer a dropout 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. In magnetic disk, tape, card, or drum systems, a dropout is a recorded signal with an amplitude less than a predetermined percentage of a reference signal. On an optical disc, it.
• The Real-time Streaming Protocol The Real Time Streaming Protocol is a network control protocol designed for use in entertainment and communications systems to control streaming media servers. The protocol is used to establish and control media sessions between end points. Clients of media servers issue VCR-like commands, such as play and pause, to facilitate real-time control of (RTSP), Real-time Transport Protocol The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over the Internet. It was developed by the Audio-Video Transport Working Group of the IETF and first published in 1996 as RFC 1889, and superseded by RFC 3550 in 2003 (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.
• Reliable protocols, such as the 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 (the other being Internet Protocol, or IP), so the entire suite is commonly referred to as TCP/IP. Whereas IP handles lower-level transmissions from computer to computer as a message makes its way (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.^[3]
• Unicast In computer networking, unicast transmission is the sending of messages to a single network destination host on a packet switching network 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 program concurrently.

• Multicast Multicast addressing is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split 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 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 boxes, and buffered media players.
• IP Multicast provides a means to send a single media stream to a group of recipients on a computer network. A multicast protocol, usually IGMP, 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 intranets), then routing protocols such as PIM can be used to deliver stream content to multiple LAN segments.
• Peer-to-peer (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 video services
• Content delivery network
• Content delivery platform
• Destreaming
• Digital television
• Grid casting
• HTTP Live Streaming
• HTTP(P2P)
• Internet radio
• Internet television
• IPTV
• List of music streaming services
• List of streaming media systems
• Multicast
• P2PTV
• Progressive download
• Protection of Broadcasts and Broadcasting Organizations Treaty
• Push technology
• Stream processing
• Webcast
• Web syndication
• Web television

References

1. ^ Josh Lowensohn. (2008). YouTube to Offer Live Streaming This Year. http://news.cnet.com/8301-17939_109-9883062-2.html?tag=mncol
2. ^ Grant and Meadows. (2009). Communication Technology Update and Fundamentals 11th Edition. pp.114
3. ^ Krasic, C. and Li, K. and Walpole, J., The case for streaming multimedia with TCP, Lecture Notes in Computer Science, pages 213--218, Springer, 2001

Categories: Networks | Applications of distributed computing | Cloud storage | Digital television | File sharing networks | Film and video technology | Internet broadcasting | Internet radio | Internet television | Multimedia | Peer-to-peer computing | Peercasting | Streaming media systems | Video on demand services

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