Learn Digital Video Editing

An Introduction To Video Compression

Have you ever exported a finished edit, only to find that the file was so big you couldn’t upload it to a website, send it to a friend, or even burn it on a dvd? Or maybe you’ve created a masterpiece, exported, and upon playback your video looks like a bunch of ugly blocks and spots. Understanding video compression and learning how to use it will help you overcome these problems.

What Is Video Compression?

Video compression is a process that reduces the amount of data contained in a video file, thus making the file smaller. It is possible to compress digital video because it contains redundant information. Imagine a tripod shot of a plane flying across a blue sky. The majority of the background remains the same from frame to frame. Instead of storing the sky data for every frame, a compressed video can re-use the sky data from a previous frame until there is a change. So if the background is unchanged for 12 frames, the information can be stored in 1 frame instead of 12. The process takes place with each individual pixel, not just frames. This allows for the most efficient reduction of data redundancy.

Does Video Compression Affect Video Quality?

Yes. By reducing the amount of video data, it’s only natural that details of the video are lost. Before you decide to give up on video compression though, take note that even DVDs contain compressed video. Generally, high quality video is less compressed and takes up more disk space. Compressing video for the internet can be a challenge because you want to make the file small while keeping quality as high as possible. We’ve all seen blocky videos on the internet, especially on sites like You Tube, where they automatically compress the clips you upload. With some testing a tweaking though, it is possible to create web videos that still look good.

Video Codecs And Compression

Video is compressed by software or devices called Codecs (Compressor-Decompressor). Each codec uses a unique algorithm to eliminate data redundancy and make the file smaller. If you have ever tried played a downloaded video and had it fail, it may have been because your computer wasn’t equipped with the proper codec to interpret the video. Some popular codecs include DVIX, MPEG-1, MPEG-2, H.264, and WMV).

How To Compress Video

Every editing program comes with some built in compression features. When you render your project, there are options that allow you to configure how your video will be compressed. The more basic programs like Windows Movie Maker simplify the process by giving you several presets (guide here). Advanced programs give you total control on the settings. There are also third party programs such as Sorenson Squeeze and Mpeg Streamclip which allow you to import videos for compression. In future posts we’ll go through some specific options and recommend a few settings.