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How Does Video Compression Work?

Video Compression Overview

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Video compression can be an art and a science; but most of us don't want to get that deep. Instead of spending hours on video compression trial and error, we want to create videos, and quickly compress them for clear images and smooth playback. If you know your video is internet-bound, there are a few things you can do when you are shooting to make it look better on a computer screen and make video compression a simple process.

First, it helps to understand the basics of video files and video compression. Video compression software examines the pixels in each frame of video, and compresses them by bunching similar pixels together in large blocks. This explains why poor video compression can give you blocky images without great detail.

Imagine video of a blue sky and lawn with a dog running across the screen. Uncompressed, the video contains information for every pixel, in every frame. Compressed, the video contains less information because similar pixels are grouped together. So, by recognizing that all pixels in the top half of the frame are blue, and all pixels in the bottom half are green, the compressed video significantly reduces the file size. The only changing pixels are those that show the dog in motion.

So, the less a video changes frame to frame, the easier video compression becomes. Of course, shooting with an eye for the inert will create some pretty boring videos. But a compromise can be reached; the following tips will help your video look better online, without stifling your creativity:

  • Get steady. Whenever possible, shoot your video on a tripod. This way, even if there's motion in the scene, the background remains the same.
  • Brighten up. Slight overexposure reduces intricate details, which means less information to process during video compression. This may run contrary to your instincts, but remember, those fine details probably won't show up anyway on a small Internet player. Also, computer screens tend to make videos look darker, so added brightness can actually improve image quality.
  • Watch your back. You may be tempted to set your subject up in front of a tree swaying gently in the breeze, but you'll need a lot of file size to capture the movement of the leaves online. Try finding a stationary background that can be easily compressed and still look good.
  • Go tight. The closer you are to a subject, the less information is on screen. In a close up with someone talking, the only motion is that of the face. Pull back, you’ll capture much more body and background movement, which will make video compression more complicated.
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