How to Calculate Internet Video Archival Storage

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We are often asked how much storage will be required to archive copies of live broadcasts online so that there is a permanent record of the live event that we had broadcast over the Internet. The math is pretty simple and we will give you that here, but first we need to point out that the single most common mistake that people make when doing these calculations is to confuse bits and bytes. Bits are a network term and Bytes are a computer term.  To convert bits to bytes divide by eight. The correct designations are: kilobits=Kb with a small “b” and  Kilobytes=KB with a capital “B”. Now that we have that straight lets create an example to show how the math works. Many of our live streaming broadcasts today are encoded and streamed at 628Kbps including video and audio. That’s kilobits per second. A four hour live broadcast would create an archive video file that is calculated this way:

Encoded video bit rate (kbps) kilobits per minute kilobits per hour convert to kilobytes convert to megabytes number of hours total storage in megabytes convert to gigabytes Computer Storage Required in GB

628

37,680

2,260,800

282,600

282.6

4

1,130

1.13

1.13

formulas

x60 seconds x60 minutes div by 8 div by 1000 div by 1000


There are a couple of other notes on these calculations that are somewhat important. The numbers above are worst case. Your storage requirements will not be greater than the 1.13GB in the example shown above, however they could be less. This is because today’s video codecs are smart. What this means is that if a number of pixels in a shot do not change from frame to frame they will not be re-encoded for each new frame. This would cause the streaming bit rate to drop with no change in image quality. Good examples of this difference are an NFL football game with lots of action and changes in every frame compared to a video of a mountain. In the NFL video case you would run up against the 628kbps encode rate. In the case of the mountain video you would be encoding at considerably less than 628kbps with no noticeable loss in picture quality.

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About the Author:

George Hall Founder/President of VideoSSC. He has over 30 years’ experience as a high technology engineering executive. With significant experience in high performance computing, Military electronics, IP networks and Video Broadcasting. Board member Public Television. An author and frequent guest on technology programs and panels. He holds a BA in mathematics from Hillsdale College.

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