Understanding What is media streaming? What is the
Media Streaming difference between streaming a media
ﬁle and playing it directly from disk?
What is media streaming? 2
How is media streaming different
from non-streaming playback? 2
What makes streaming media
Media Servers 4
Media Streaming with the
ScreenPlay Pro HD 5
March 31, 2009
What is media streaming?
Media streaming allows you to play back an audio or video ﬁle from the internet (or from
a network location) without having to ﬁrst download the complete ﬁle to your computer.
When a media ﬁle is streamed, it is delivered as a constant data stream to your computer
or media player rather than as an intact ﬁle that you must save and decompress before
you can play it. For example, a live television broadcast might be streamed over the
internet and viewed on your computer while the broadcast is in process.
How is media streaming different from non-streaming playback?
Media streaming developed as a means of delivering audio and video via the internet
without having to ﬁrst download and decompress a large ﬁle on your computer. Because
media ﬁles (especially video) tend to be very large, it typically takes a very long time to
download a ﬁle that might provide only a few minutes (or even seconds) of video. Media
streaming makes it possible to start playback of a media ﬁle from the internet almost
immediately with only a brief delay needed to buffer the data stream. Media streaming
also means that a ﬁle you want to play doesn’t have to reside on your personal computer.
Rather it is stored on a server that delivers the data stream ‘on demand’ when you want
to view or listen to it.
A multimedia ﬁle can be streamed or not streamed, depending on how it’s delivered
to your media player. A good example of the difference between streaming and non-
streaming media is viewing a video ﬁle on YouTube versus downloading the video as a ﬁle
to your computer then viewing it. When the video is delivered over the internet as you
view it (YouTube), it is streaming media. When you play the video as a ﬁle saved on your
computer, it is non-streaming.
Discussions of media streaming often use technical terms that are unfamiliar to many
users. Here are some of the more common terms.
Bit rate (bitrate or data rate)
This is a measure of how fast data is being streamed. It most often refers to the
number of bits that are conveyed or processed per second. Examples:
• kbps or kbit/s = kilobits per second
• Mbps or Mbit/s = megabits per second
• Gbps or Gbit/s = gigabits per second
Buffering is the process of collecting a small backlog of data on the end-user system.
This supports continuous playback in case of delays or interruptions in the data
stream (for example, due to network congestion). The media player reads from the
buffer while the buffer reﬁlls from the media streaming provider.
Buffer underrun (buffer underﬂow)
Buffer underrun occurs 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 sometimes serious side effects, since
the data being buffered is generally not suited to stop-start access of this kind.
Understanding Media Streaming 2
A measure of available or consumed data communication resources, usually
expressed in bits per second or a multiple of it (kbps, Mbps, Gbps). Bandwidth
capacity or available bandwidth usually refers to the maximum throughput in a digital
communication system. Consumed bandwidth generally refers to the average data
rate of successful data transfer through a communication path.
Data compression or source coding is the process of encoding information using fewer
bits (or other information-bearing units) than an unencoded representation would use
through use of speciﬁc encoding schemes. As with any communication, compressed
data communication only works when both the sender and receiver of the information
understand the encoding scheme. For example, this text makes sense only if the
receiver understands that it is intended to be interpreted as characters representing
the English language. Similarly, compressed data can only be understood if the
decoding method is known by the receiver. See Understanding Codecs in this white
paper series for more information on this topic.
CPU stands for central processing unit (or processor, for short) and refers to an
electronic circuit that can execute computer programs. The CPU is the ‘brains’ of a
computer system. CPU power is how fast a processor is capable of executing. Higher
CPU power boosts the processing speed for streaming media.
In the context of media streaming, dropout refers to a momentary loss of signal,
usually caused by noise, propagation anomalies, or system malfunctions. For digital
signals, dropouts can be sudden and complete.
Refers to algorithms or computer programs that are applied to detect and ﬁx errors
in the data stream. This has great practical importance in maintaining data integrity
across noisy channels and less-than-reliable storage media.
A local area network (LAN) is a computer network covering a small physical area, like
a home, ofﬁce, or small group of buildings, such as a school, or an airport.
Low latency allows human-unnoticeable delays between an input being processed and
the corresponding output providing real time characteristics. In the context of media
streaming, low latency interrupt paths are critical for preventing buffer underruns.
This refers to protocols that arrange for prerecorded streams to be sent between
computers. This prevents the server and its network connections from becoming a
bottleneck. In general, the data feed will come from multiple clients or peers rather
than a single server.
A protocol is a standard by which communication takes place between network
devices. HTTP, TCP/IP, FTP, UPnP, and DNLA are all examples of commonly used
network protocols. See Understanding Network Protocols in the “Networking 101”
white paper series for more information on this topic.
Understanding Media Streaming 3
Throughput is the average rate of successful data delivery. Throughput for delivery of
streaming media depends on the capabilities of the media server, the protocol used
for transmission, network bandwidth, and client (end-user) CPU power.
Unicast – Multicast
Unicast transmission is the sending of information packets to a single destination.
Unicast servers provide a stream to a single user at a time, while multicast servers
can support a larger audience by serving content simultaneously to multiple users.
Video on demand (VOD)
A media stream can be ‘on demand’ or ‘live’. On demand streams are stored on
a server for a long period of time, and are available to be transmitted at a user’s
request. Live streams are only available at one particular time, as in a video stream of
a live sporting event.
What makes streaming media choppy?
Interruptions in streaming media playback are far from uncommon, especially for
video streamed from the internet. Stop-and-start “rebuffering” delays result when the
throughput of the delivered data stream is lower than the playback bitrate. In less
technical terms, if your media player is playing a ﬁle faster than the media server is
delivering the data stream, your player frequently has to stop to let the media data
stream catch up.
The opposite problem can also occur. If the media server transmits a data stream faster
than your system can receive or process it, some information packets will be lost. This can
result in poor video quality and possibly even jumps in playback.
Media servers are specialized for optimized delivery of audio and video content to a media
player. With a media server connected to a home network, you can use the media server
to consolidate media ﬁles from individual computers on the network, so you can access all
of your media content from any media networked device. Several Iomega products include
media server capabilities and can stream audio and video ﬁles over a home network.
For example, the Iomega® Home Media Network Hard Drive can be conﬁgured to share
media ﬁles with iTunes or DLNA clients for playback on your computer, TV, or Stereo. You
can use this feature to set up the iTunes libraries stored on computers throughout your
home network so they are accessible by all users on the network.
The Iomega® StorCenter™ ix2 and StorCenter ix4 series NAS Servers include a built-in
media server that scans for media ﬁles in speciﬁed Shared Folder directories. Any media
content contained in these directories will be scanned by the Iomega StorCenter media
server and accessible to any user on your network with a media player. The Media Server
supports playback of videos, music and pictures from any UPnP AV (Universal Plug and
Play Audio Visual) network media players, such as iTunes®, Windows Media Player®, or
The Iomega® ScreenPlay™ Pro HD is a specialized media player that is capable of
streaming audio and video ﬁles across a network to play on your TV. You can use this
capability to tie your home network into your home entertainment system. See the next
section for detailed instructions.
Understanding Media Streaming 4