Decompression, storage and bandwidth

Audio or video data has to be compressed to be transmitted and so after transition it is being decompressed by the media player during comprehensive but fairly straightforward process. This is a job for codec which compresses the file and encodes it to the right format. For compressing the video files two groups of compression schemes can be used: scalable and nonscalable video coding.

Even encoded media data are not small files so critical with streaming media is to understand terms of bandwidth and storage capacity.

Bandwidth is a rate at which data is sent to or received from the internet. It is measured in Megabits (Mbs) and represents the number of bits transmitted in a second (Online Technologies Corporation, 2006). ‘Bandwidth is, essentially, the amount of information that can pass through a particular point of the wire in a specific amount of time’ (RealPlayer Manual, 2007). The bandwidth of the stream is determinate by the speed of the internet connection. Clearly the higher the bandwidth the better.

According to Wikipedia streaming media storage size is calculated from streaming bandwidth and the length of the media as follow:

STORAGE SIZE (MB) = LENGTH (sec) x bit rate (kbs) / 8,388.608

For example:
One hour of video encoded at 300 kbit/s (typical broadband video and it's usually encoded in a 320×240 pixels window size) will be:
         (3,600 s · 300 kbit/s) / 8,388.608 = 128.7 MB of storage
If the file is stored on a server for on-demand streaming and this stream is viewed by 1,000 people using a Unicast protocol, you would need
         300 kbit/s · 1,000 = 300,000 kbit/s = 300 Mbit/s of bandwidth
This is equivalent to 125.73 GiB 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 bandwidth. See below for more information on these protocols.