DivX is the name of a specific video compression codec (compression-decompression) developed by DivX, Inc.
The format was developed to enable users to create very high quality video with very small files sizes.
The DivX codec is currently the most popular MPEG-4 based codec because of its quality, speed and efficiency. As is usually the case the popular becomes more popular because… well… it’s popular! So as a result most modern DVD players and devices are now compatible with the DivX standard.
DivX is based on the H.264 standard which in itself is an MPEG4 variant. It is important to note that terms like MPEG2 and MPEG4 are not codecs in themselves although the terms are used in this context quite often. Both MPEG2 and MPEG4 are a set of rules or standards that dictate the manner in which particular video files are encoded and rendered (played back).
What is H.264?
To be blunt H.264 is probably the future. It is most likely that the current MPEG2 for DVD and DV avi video files types for camcorders will be phased out in favor of H.264 or something similar.
H.264 provides very powerful compression technology that delivers superior video at a low bit rate. It can run across many different types of platform and is suited to high definition production.
The H.264 standard reduces the amount of information required to reproduce a video…
How Does it Work?
The H.264 encoder is able to divide each picture recorded into a set of blocks, it then searches the pictures in the video stream before and after the picture being encoded.
It detects the changes between the before and after pictures as compared to the current picture and carries out what is called “motion estimation.” That’s just a fancy was of saying it makes a calculated guess as to what the changes are.
H.264 inspects the before and after pictures down to the level of one quarter of a pixel for this motion search resulting in quite amazing quality.
Once it has done that it now “knows” what is the same and what is different between one picture and the next and simply put, it throws out everything that is the same and only keeps what is different.
When the file is played back the decoder in the playback device will hit the picture in the example above. It will display a little of the total picture from the information in the file but mainly it will go to other pictures (before and after the current one) to find the rest of the information it needs to show the complete picture.
That is how it manages to achieve such small video file sizes.
It is a common misconception that H.264 is a format with only a single form. Not true .Mov files are H.264 and very often you will find that files you see that are marked as MPEG4 are actually H.264.
H.264 can occur under a number of guises displaying a wide range of parameters.
For a complete look at this style of compression you can take a look at this post here under MPEG2 and MPEG4 Editing or here for Video File Formats Explained.
As a video file encoding format H.264 represents probably the best quality for file size trade off on the market today and the DivX implementation of H.264 represents the best of the best.
The Downside
Like all highly compressed video file formats DivX was not designed in any way as an editing format. It is what is called a distribution format and is intended as the video file format to be used in the final product.
Editing DivX files can be a nightmare and the reasons for this are explained in the links above in this post.
Compatibility with Other Video Editing Software
Because DivX is a specific codec it is easily implemented into your existing video editing software. All you have to do is download the codec from www.DivX.com and install. From that point forward when you choose to render a final video file of a project DivX will appear as one of the choices for file output.
Each type of video editing software will have a slightly different place in which you will gain access to imported codecs so just check your particular software documentation for details.
