User guide

CODEC & CONTAINER FORMATS
When you hear people talk about the format of a digital video, they
are 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
(squeezing all that raw data into a compressed, transportable form)
and decoding (reading and playing the data that has been
compressed). 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 videoare packaged in a MKV container
along with AAC audio.
DivX 10
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DivX, LLC User Guide