Streaming Media - Streaming Bandwidth and Storage

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.

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)

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