Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider. 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, as most other delivery systems are either inherently streaming (e.g., radio, television) or inherently non-streaming (e.g.,
books, video cassettes, audio CDs). The verb 'to stream' is also derived from this term, meaning to deliver media in this manner. Internet television is a commonly streamed medium.
Live streaming, more specifically, means taking the media and broadcasting it live over the Internet. The process involves a camera for the media, an encoder to digitize the content, a media publisher where the streams are made available to potential end-users and a content delivery network to distribute and deliver the content. The media can then be viewed by end-users live.
Security remains one of the main challenges with this new methodology. Digital rights management (DRM) systems are an example of a solution to keep this content secure.
Streaming bandwidth and storage
A broadband speed of 2.5 Mbps or more is recommended for streaming movies, for example to an Apple TV, Google TV or a Sony TV Blu-ray Disc Player, 10 Mbps for High Definition content.
| 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 2]
Real world example:
One hour of video encoded at 300 kbit/s (this is a typical broadband video as of 2005[update] 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 MiB 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. Of course, using a multicast 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 last for 3 hours, with 3000 viewers then the calculation is:
- Number of MB transferred = encoder speed (in bps) × number of seconds × number of viewer / (8*1024*1024)
- Number of MB transferred = 500.000 (bps) × 3 × 3600 ( = 3 hours) × 3000 (nbr of viewers) / (8*1024*1024) = 1931190 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 WebM.
Encoded audio and video streams are assembled in a container bitstream such as FLV, 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.
