Although professional video production is a very technical field, with a high degree of expertise required to be successful, there are still a few areas that perplex and confuse even the most experienced production professionals. One of these is video compression, which is both misunderstood and misused on a significant proportion of projects. Fortunately, compression doesn't have to be as complicated as it seems, and understanding a few basic principles can make the whole concept simpler and easier to apply practically.
Accordingly, we at DVT have put together this quick guide covering the basics of compression, when it's necessary, and a few golden rules to keep in mind.
In the broadest possible definition, compression is the process of taking an image and making it take up less storage space.
What is video compression
Video compression is often regarded as a negative process, one that strips away the detail, data and quality from video in favour of smaller files and ease-of-use. This is partially true, but there's far more to the compression story than meets the eye. In the broadest possible definition, compression is the process of taking an image and making it take up less storage space. Inevitably, this does mean that there will be a loss of data, but this has always been true when capturing video, and when understood correctly, doesn't have to be a bad thing.
Compression is often thought of as a process that takes place in the digital realm, but the truth is that compression happens at multiple points during the image capture process. For example, B&H Explora points out that an image undergoes a form of compression when it enters the lens of your camera – unless you happen to be using a 1:1 macro.
So, is compression really bad? Again, the answer is a complex one. If done poorly, compression can have a significant negative effect on the quality of your image, but when managed correctly, there's really no reason to fret.
In fact, if it wasn't for compression, the world of video would be a very different place. Just think about how much more internet bandwidth it would take to stream video on Netflix or YouTube if there wasn't some way to reduce the file size.
How does compression work?
To make compression work for you, it's a good idea to start by understanding how it works in practice. Typically, when we talk about compression in film production, we are referring to the compression and then decompression of files in order to make them easier to work with, by significantly reducing their size. These two processes are done by special pieces of software called codecs, which you can read about in our recent article on the subject.
To keep things in simple terms, these codecs make video files smaller by eliminating information that is redundant. For example, data that is repeated across multiple frames.
Once a video file has been compressed to a manageable size, ideally without the loss of too much important data, you'll be able to more easily work with it during the editing process. So, doesn't it make sense to compress your video files as much as possible, in order to best work with them during post-production? The answer to this question is no, and to understand why, we're going to give you three golden rules to consider every time you compress a file, or when selecting a codec.
The three golden rules of compression
Rule number one when working with compression is simple – whenever you compress, you are irretrievably losing data. This means that if you decide to heavily compress your files in order to make your editing program run quicker, or to save on storage space, you won't be able to get the quality to look as good as the original captured files, which will already have been compressed in one form or another anyway. Therefore, try to compress your footage as few times as possible.
The higher the quality of your original file, the higher the quality of your compressed file.
In the video above, editor Larry Jordan uses the metaphor of compression as a transition between different vessel sizes. Your original file is a bucket of water, and compression is the process of pouring that bucket of water into a small mug. You will inevitably loose data (water), and even if you then pour that mug back into the bucket, you'll still only have a mug's worth of information.
The second rule is that the higher the quality of your original file, the higher the quality of your compressed file. It's simply not possible to make a compressed file look better than it did originally, so start with lots of data and compress from there.
Finally, rule number three is to compress based upon what you want your finished file to be. If you know that you'll be putting the finished product on YouTube or Vimeo, take a look at the platform's compression guidelines before exporting to make sure you're uploading a file that will look its best when viewed by an audience.
Hopefully this guide has helped you to understand that compression is a necessary part of video production, and doesn't have to be all bad. If you'd like to find out more about making your video projects look as good as they possible can, contact the DVT team today.
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