Video Compression: Knowledge for Beginners
Video compression is the fundamental pillar in what makes digital video possible. It allows you to take high quality video and then compress it into a small file size, which can then be placed on DVDs or uploaded to the Internet with no or minimal loss of quality. Video compression begins with transcoding. Transcoding is the process of converting one digital file format into another one. The video gets compressed and is later uncompressed when it is played back by a video player that recognizes that file format.
Regardless of whether a movie was initially shot on film or video, the movie's footage gets digitized and edited on a computer. Usually lower quality files are used for creating the initial edit of the movie for hard drive space and storage reasons, but eventually the highest possible quality files will replace the lower ones for the final edit. All that footage uncompressed takes up a lot of hard drive space. A typical DVD only has the capacity to store 4.7GB worth of information. Depending on the quality of the video, that could only be less than ten minutes of footage in some cases.
The solution is the MPEG compression, specifically MPEG-2. When you transcode your edited movie into this format, you create a file that has high quality video without taking up the hard drive space. MPEG-2 makes it possible to store a feature length film on a DVD disc without losing quality.
Compression and the Web
Web video also needs to be compressed in order for it to work. One reason is that larger sized videos take up too much space on a server. Another reason is that the larger the file, the longer it takes for a viewer to see it. People will often run out of patience before the video loads and no one will see the work.
The goal for compression on the web is to get a small file size that can load quickly without sacrificing quality and resolution. Flash video is great for this, but it's one drawback is that not all video sharing sites support the format. It's also been forsaken by Apple, which means that some people can't even watch it.
A great and recent CODEC is H.264 compression. This allows video users to apply the CODEC to Flash, Quicktime and MP4 files so that they can remain small in size and high in quality. It helps facilitate the goal of making high quality video that loads quickly.