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This is one of the most difficult questions to answer, and one of the most frequently asked.

The bandwidth you will use is almost impossible to accurately estimate, because it depends on the following variables:

1. Bitrate(s) at which you broadcast (or stream on demand)
2. How often and long your media is available (24/7 for on-demand media, during broadcasting hours for live broadcasting)
3. Number of listeners or viewers
4. The length of time your visitors listen to or view your stream(s)

If you can estimate those four variables, you can calculate bandwidth usage, but be aware that reality may not match your estimate.  It's difficult to estimate how many people will be interested in your media, and how long and how frequently they'll access it.

However, for the sake of understanding streaming media bandwidth, let's walk through a calculation using some estimates.

For simplicity, let's assume you're a church, you'll be broadcasting or streaming on-demand at 40 kbps, which is a low enough bitrate to support most dial-up internet customers, and that you'll broadcast about 10 hours of services per month to an average audience of 10.

The formula to determine bandwidth utilization, in bytes, for a given number of listeners/viewers, for a given length of time, is:

Bitrate * 128 * 3600 * number of listeners/viewers * number of hours

The 128 is a factor which converts kilobits into bytes.  (1 kilobit = 1024 bits, 8 bits = 1 byte, therefore 1024 bits / 8 = 128 bytes).

Therefore, 40 kilobits per second equates to 5,120 bytes per second.

The 3600 converts the bytes per second into bytes per hour (60 seconds to a minute * 60 minutes to an hour).

Now we're at 18,432,000 bytes, or roughly 17.5 megabytes.  This gives us the hourly bandwidth utilization for a single listener.

Now, factor in an average of 10 listeners, and we have 184,320,000 bytes, roughly 175 megabytes.

Factor in a total of about 10 hours per month, and we're up to 1,843,200,000 bytes, or about 1.7 gigabytes.

This is less than 10% utilization of a basic MEDIASERVE streaming package, which provides 20 gigabytes of monthly bandwidth.

Are you totally confused?  If you are, don't worry, it's a complicated calculation.  The calculation can really only tell you what you will use if your assumptions are correct.  It's not likely your assumptions will be correct, because it's so difficult to accurately predict usage patterns.

However, using the calculation can help you get an idea of what can be done within the bounds of the default bandwidth provided, and what might require additional bandwidth.

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