User guide

DivX Plus Player for Windows
25
DivX, LLC User Guide
COMMON DIGITAL
VIDEO TERMS
CODEC & CONTAINER FORMATS:
When you hear people talk about the format of a digital video,
they might be referring to either the container file or to video
or audio codecs. The container format is like the wrapper that
holds both the video and audio streams together. The video
and audio would be two separate entities that don’t know how
to play together without the container. The container not only
holds these two together, but contains enough data to make
sure they are both encoded and decoded together as a single,
synchronized unit.
A “codec” is short for ‘compressor-decompressor”, or
sometimes ‘coder-decoder’. In order to explain why this is
important to digital multimedia, let’s first take a step back.
In their raw form, digital videos are very large. This not only
becomes a problem with storage, but can particularly pose a
problem where playback is concerned. Large files require beefy
processors and a lot of memory—more than most people have
on their personal computers. In order to resolve this problem,
computer geniuses developed fancy algorithms to “compress”
the digital video files down to a more manageable level.
Digital video is compressed to economize on space, whether
it’s bandwidth or media, and a codec does the job of encoding
and decoding. They remove a lot of extra data that isn’t too
important, while retaining the most important parts of the video
in a condensed form. (By any chance do you remember Mary
Poppin’s mysterious bag that held more in it than seemed
physically possible? It’s kinda like a high-tech version of that…)
By improving the techniques upon which the codec is based,
we’re able to transmit higher quality video using the same
bandwidth as before. Typically both the encoder and decoder
will become more complex, but this is okay because computers
are always getting faster.
So, going back to the concept of a codec, compression is
used to make the video file manageable, and a de-compressor
is used to unpack its many little parts, allowing software or
electronics devices to play it back beautifully on your screen.
There are many video and audio codecs out there. You might
already be familiar with the format called MPEG-2, which
is used for DVDs. The MPEG-4 format is another type of
compression, like a distant cousin that can make videos even
more compact than its MPEG-2 counterpart. The original DivX
codec is a specific compression format based on MPEG-4
Part 2 (ASP) standards. These videos are packaged in an AVI
container (or the DIVX container, which is a type of AVI) along
with MP3 or AC3 audio. In 2009, DivX, Inc. released their own
version of the H.264 codec based on MPEG-4 Part 10 (AVC)
standards for optimum high definition video. The H.264 videos
are packaged in a MKV container along with AAC audio.