Streaming media

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A typical webcast, streaming in an embedded media player

Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a provider. Its verb form, "to stream", refers to the process of delivering media in this manner; the term refers to the delivery method of the medium rather than the medium itself.

A client media player can begin playing the data (such as a movie) before the entire file has been transmitted. Distinguishing delivery method from the media distributed applies specifically to telecommunications networks, as most other delivery systems are either inherently streaming (e.g., radio, television) or inherently nonstreaming (e.g., books, video cassettes, audio CDs). For example, in the 1930s, muzak was among the earliest popularly available streaming media; nowadays Internet television is a common form of streamed media. The term "streaming media" can apply to media other than video and audio such as live closed captioning, stock ticker, and real-time text, which are all considered "streaming text". The term "streaming" was first used in the early 1990's as a better description for video on demand on IP networks; at the time such video was usually referred to as "store and forward video"[1], which was misleading nomenclature.

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 to distribute and deliver the content.

Contents

History

In the early 1920s George O. Squier was granted patents for a system for the transmission and distribution of signals over electrical lines[2] which was the technical basis for what later became muzak, a technology streaming continuous music to commercial customers without the use of radio.

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:

However, computer networks were still limited, and media were 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-ROMs.

New technologies

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

"Severe Tire Damage" 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) 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 was also a pioneer in the streaming media markets, when it broadcasted a baseball game between the New York Yankees and the Seattle Mariners over the Internet in 1995.[3] They went on to launch streaming video technology in 1997 with RealPlayer. Other commercial streaming pioneers included Starlight Networks, VDO-Net, Protocomm, Broadcast.com and Vivo.

The first symphonic concert on the internet took place at the Paramount Theater in Seattle, Washington on November 10, 1995.[4][verification needed] The concert was a collaboration between The Seattle Symphony and various guest musicians such as Slash (Guns 'n Roses, Velvet Revolver), Matt Cameron (Soundgarden, Pearl Jam), and Barrett Martin (Screaming Trees).

When Word Magazine launched in 1995, they featured the first-ever streaming soundtracks on the Internet. Using local downtown musicians the first music stream was "Big Wheel" by Karthik Swaminathan and the second being "When We Were Poor" by Karthik Swaminathan with Marc Ribot and Christine Bard.[citation needed]

Business developments

Microsoft developed a media player known as ActiveMovie in 1995 that allowed streaming media and included a proprietary streaming format, which was the precursor to the streaming feature later in Windows Media Player 6.4 in 1999. In June 1999 Apple also introduced a streaming media format in its QuickTime 4 application. It was later also widely adopted on websites along with RealPlayer and Windows Media streaming formats. The competing formats on websites required each user to download the respective applications for streaming and resulted in many users having to have all three applications on their computer for general compatibility.

Around 2002, the interest in a single, unified, streaming format and the widespread adoption of Adobe Flash prompted the development of a video streaming format through Flash, which is the format used in Flash-based players on many popular video hosting sites today such as YouTube. Increasing consumer demand for live streaming has prompted YouTube to implement a new live streaming service to users.[5] Presently the company also offers a (secured) link returning the available connection speed of the user.[6]

Consumerization of streaming

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 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 for both storage and streaming.

Increasing consumer demand for streaming of high definition (HD) content has led the industry to develop a number of technologies such as WirelessHD  or ITU-T G.hn, which are optimized for streaming HD content without forcing the user to install new networking cables.

Today, 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 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).[7]

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 or a Sony TV Blu-ray Disc Player, 10 Mbit/s for High Definition content.[8]

Unicast connections require multiple connections from the same streaming server even when it streams the same 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 megabytes) = length (in seconds) × bit rate (in bit/s) / (8 × 1024 × 1024)[note 1]

Real world example:

One hour of video encoded at 300 kbit/s (this is a typical broadband video as of 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) requires around 128 MB 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 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 per hour. Using a multicast protocol the server sends out only a single stream that is common to all users. Therefore 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 MBs transferred = encoder speed (in bit/s) × number of seconds × number of viewers / (8*1024*1024)
Number of MBs transferred = 500,000 (bit/s) × 3 × 3,600 ( = 3 hours) × 3,000 (nbr of viewers) / (8*1024*1024) = 1,931,190 MB

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.

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:

Multicasting broadcasts the same copy of the multimedia over the entire network to a group of clients

A typical application, and new marketing concepts

Useful - and typical - applications of the "streaming" concept are, for example, long video lectures performed "online" on the internet.[11] An advantage of this presentation is that these lectures can be very long, indeed, although they can always be interrupted or repeated at arbitrary places.

There are also new marketing concepts. For example the Berlin Philharmonic Orchestra sells internet live streams of whole concerts, instead of several CDs or similar fixed media, by their so-called "Digital Concert Hall" [12] using YouTube for "trailing" purposes only. These "online concerts" are also spread over a lot of different places - cinemas - at various places on the globe. A similar concept is used by the Metropolitan Opera in New York.

See also

Notes

Footnotes

  1. ^ 1 megabyte = 8 × 1024 × 1024 bits.

Citations

  1. ^ "On buffer requirements for store-and-forward video on demand service circuits" (in English). IEEE. http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=188525&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel2%2F536%2F4777%2F00188525.pdf%3Farnumber%3D188525. Retrieved 1991.
  2. ^ "US Patent 1,641,608" (in English). Google Patents. http://www.google.com/patents?id=5pV5AAAAEBAJ&dq=1641608. Retrieved 2007.
  3. ^ "RealNetworks Inc.". Funding Universe. http://www.fundinguniverse.com/company-histories/RealNetworks-Inc-Company-History.html. Retrieved 2011-07-23.
  4. ^ http://www.seattlepi.com/archives/1995/9511130063.asp[dead link]
  5. ^ Josh Lowensohn (2008). "YouTube to Offer Live Streaming This Year". http://news.cnet.com/8301-17939_109-9883062-2.html. Retrieved 2011-07-23.
  6. ^ https://www.youtube.com/my_speed#
  7. ^ Grant and Meadows. (2009). Communication Technology Update and Fundamentals 11th Edition. pp.114
  8. ^ Mimimum requirements for Sony TV Blu-ray Disc Player, on advertisement attached to a NetFlix DVD[not specific enough to verify]
  9. ^ Ch. Z. Patrikakis, N. Papaoulakis, Ch. Stefanoudaki, M. S. Nunes, “Streaming content wars: Download and play strikes back” presented at the Personalization in Media Delivery Platforms Workshop, [218 – 226], Venice, Italy, 2009.
  10. ^ 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
  11. ^ A typical one-hour video lecture is the following "live stream" from an international conference on financial crises: [1].
  12. ^ The corresponding internet link is http://www.digitalconcerthall.com/

Further reading

External links