PRACTICAL DV FILMMAKING

Practical DV FilmMaking

• Overview
• Inside video
• Films and how they work
• Pre-production
• Production tools
• Production aesthetics
• Post-production tools
• Post-production aesthetics
• Careers and distribution
• Mapping the industry
• Glossary of film and video terms

call this process 'compression-decompression', shortened to 'codec', to describe the various ways we have of doing it. Many companies produce codecs for use with video and each use the standards that MPEG established. Some are good for one type of movie, others better for other types.

MPEG

The Emmy Award-winning MPEG group worked out several methods of compressing data for moving images and came up with a few different standards. Let's take a look at the main ones:

MPEG-1

This is a popular method used for encoding video for CD-ROM and for VCD, the format widely used in Asia. It is the main method used for web video with the suffix '.mpg' and also gave rise to the standard known as MPEG-1, layer 3, or MP3, which is the most widely used method for compressing music files.

MPEG-2

This method is a development of MPEG-1 which grew into the way we compress video for set-top digital TV boxes and for the DVD. It is probably the most widely used compression in the world, with the spread of the consumer DVD outstripping VHS, and the imminent digitization of TV broadcasting. At the moment there is no need for an MPEG-3 because this method is seen to perform well with high definition television, which will become more widely used in the near future.

MPEG-4

The need for this standard came about as we started to use moving images on the web and in mobile web devices. The format handles multimedia items very well and is ideal for gaming, broadcasting via the web and pages that contain media items. The best aspect of this method is that you can decide how compressed you want the video to be. This is called enhanced scaleability, and is popular with media providers because various options can be given for the user, depending on what sort of connection they have. They can opt for high compression for small bandwidth (a smaller file for 56k) or low compres­sion (a bigger file for ADSL/broadband).

MPEG-7

This is another multimedia standard that enables the user to personalize and filter what they receive. It is ideal for web-based video, where it interacts with other media content.

How MPEG-4 and -2 operate

Let's now look at the most advanced way of compressing video to see what the most useful method does for your film.

To begin with, the codec looks at the information on several frames at a time, a group of pictures (GOP), in a process known as 'interframe compression'. It does this by breaking up a sequence into I, B and P frames