Video file formats: part two

Understanding video file formats - Part Two

DivX

DivX is a codec that was created by a company of the same name and uses one aspect of the MPEG-4 specification. Like H.264, it is a standard that uses compression to make the file sizes much smaller, but still retains a fairly high level of quality.

Some standalone DVD players will play this format. When we talk about the compression of video files, the term ‘lossless’ is often mentioned. This means that although the overall file size is smaller than the original, this has been achieved without losing any data. H.264 is a lossless format, but DivX is a ‘lossy’ format, meaning that some of the data from the original file is lost in compression.
 

WMV, AVI and QuickTime

WMV is a Windows-only format generally used for streaming video over the internet. Again, it is a compressed format though Microsoft claims that the bit-rate is twice that of MPEG-4, meaning that the overall quality is higher even though file sizes are larger. It is the default format for Windows Media Player but doesn’t work on Apple’s QuickTime Player, though the third-party plug-in Flip4Mac WMV (www.flip4mac.com) will solve this problem.

AVI is another Windows-only format but is older and not so commonly used these days. Apple’s media player, QuickTime, isn’t just restricted to the Mac OS but works on Windows as well. It’s free to download and can deal with most major file types including AVI files, though additional plug-ins are required for more obscure types.