Lossy Vs. Lossless Video Compression
Video compression is one of the most difficult and highly debated subjects in the world of media and technology. This is caused, in part, by a multitude of different compression standards and the subtle differences in how various people perceive those differences. To say that one compression method or setup is better than another is akin to comparing one style of painting to another. While the two styles have defined differences, the beauty is in the eye of the beholder.
One thing can be said for all video compression: lossy compression gets gradually worse the more you encode it. If you have a source video from your camcorder, and you encode it to a lossy intermediate codec that your video editor understands, then encode it again to a final product that you upload to YouTube, you’ve essentially reduced the quality of the video twice. Even if you match or exceed the bit rate each time, the compressor will work to copy the source file in a new way, essentially making a copy of a copy. To further this problem, YouTube does its own lossy compression on videos it receives, which can create even more quality loss.
Dirac (Can be lossless)
Think about lossless creation as an exact pixel-by-pixel copy of the original file. Each pixel is taken from the source and placed in the new file exactly where it existed in the source file. A lossless compression may significantly increase file size, resulting in giant files that sometimes dwarf the source, even if that source itself was a tiny compressed file.
Commonly used lossy video compression methods include (not a full list):
Lossy compression methods don’t make pixel-by-pixel copies of the source at all. They work in several different ways, but the general result is the same. By making a copy that is “good enough,” a lossy compression method can essentially turn a giant source file into something that takes up considerably less space and can be easily played back on a portable device. In fact, most portable media players require a lossy compression format in order to play back the video due to RAM and processing constraints. You might even find it difficult to play a lossless video on a desktop computer, as most media players have trouble processing massive amounts of information.
Over all, lossless compression is best for every stage of the editing process from capture to edits, but lossy compression formats are currently the best way to deliver high-quality video to your portable media player or to YouTube.