No, I'm not talking about Tupperware. A multimedia file
container is a computer file that holds various types of data within. These data types usually consist of video and
audio streams, as well as other types of media including subtitles, pictures,
and menus.
Although usually used for audio/video, a container format
can technically hold any sort of data. Even if you haven't heard of the term,
you are probably familiar with a few container formats. Some popular
multi-media containers include AVI, VOB, MP4, MKV, FLV, and ASF.
The container format specifies the types of data within and
the way it is stored, but not specifics on how to view the individual streams. That
is where video codecs come in, which are often confused for containers
themselves.
Video Codecs
A video codec is a way of compressing and decompressing digital video so
that the overall file size is smaller than the original uncompressed video. Most
video codecs use lossy compression; meaning that after uncompression, the video
has lost some of its original quality. Although there are lossless video codecs
such as HuffYUV and Lagaraith, they are much less common as some quality loss
is generally accepted for having more manageable files.
Various codecs can be used within any given video container
as long as the codec is supported by the container specifications.
DirectShow Filters
DirectShow is a multimedia framework developed by Microsoft that is a standard
component in all versions of Windows operating systems since Windows 98.
DirectShow takes complex multimedia tasks, such as video playback, and divides
it up into a number of separate steps known as filters. Each of these filters
can be thought of as one step of processing the data in the container for
playback.
DirectX is required to play media using DirectShow. It is
recommended that you have at least DirectX 9.0, which comes preinstalled on
Windows XP SP2. Vista users already have DirectX 10 preinstalled on their
system.
Almost all codecs can be implemented as DirectShow filters,
but filters also have other uses as well - such as deinterlacing video or combining
several video or audio streams.
With so many different media containers available to choose
from, how do you decide which one is best? Over the next several weeks, I will
take a closer look at some of the popular containers and go over the advantages
and disadvantages of each.
Are there are any specific video formats you prefer or would
like to see discussed? Leave a comment.
More Info:
AfterDawn: Container
Wikipedia: Container Format (digital)
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