Video Compression Explained, Or How To Squash An Elephant
I wanted to send an elephant to a friend. The postage was pretty severe, so I got a life size picture of one instead. This was almost as good as the real thing, but it wouldn’t fit through his letterbox. So I got a postcard made up.
This is about the best metaphor I can come up with for the video workflow in terms of data management. We film in as high an image quality as we can afford, but high quality also means high data rates, (the flow of data through your computer as the video plays). If you’re filming for non-broadcast use a typical data rate would be around 28Mb per second. Thus video editing suites need to be very high powered computers which are able to manipulate this material without crashing.That’s why we compress video before delivery.
Compression is when we make our elephant into a postcard.
The function of video compression is to make the file size and data rate suitable for the viewing platform. This is done by using a software called 'Codec'.
Different codecs and file formats use different means of compression and the resulting files have different qualities making them suitable for different uses.
To give one example – the flv (Flash Video) format from Adobe offers excellent options for high quality with low data rate and file size, but Apple does’t like Adobe products. So you wouldn’t use it to encode video for iPhones or iPads.
And that’s how to squash an elephant.
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