Codec: XviD
XviD is an MPEG-4 video codec originally
based on OpenDivX. It is a project that was started by a group of volunteers
after the OpenDivX source was closed. Many of these people accused DivXNetworks
of starting OpenDivX for the sole purpose of stealing other people's ideas for
use in their commercial DivX 4 codec, and vowed to make a free and open-source
alternative; Xvid. Xvid is DivX spelled in reverse as a rather sarcastic
tip-of-the-hat to the codec's origins. In May 2004 after a string of betas,
XviD 1.0 Final was released. This and its subsequent releases constitute a very
stable and relatively quick MPEG-4 encoder and offer more features and quality
settings than the freely downloadable version of DivX. Both DivX and Xvid are
ideal for storing video at very high quality, using relatively low disk space.
XVid can be downloaded free of charge from www.xvid.org/Downloads.15.0.html.
Codec: DivX;-) and DivX
DivX was originally a codec derived from
Microsoft's pre-MPEG-4 release ASF video format. When Microsoft first released
the format, although the improvements over existing technology for handling low
bitrate video were beyond debate, it was only possible to use the codec with
the Windows Media Encoder, a piece of software that, although powerful, did not
allow users to create high quality, low-bitrate rips of DVDs. Finally, a French
hacker named Jerome Rota cracked the ASF codec to allow people to use the
MPEG-4 based encoder without restriction. The final product allowed users to
save the resulting high quality files in the popular AVI format, allowing them
to be edited in almost any movie package, provided you had the codec installed.
It also allowed users to substitute the ASF audio stream which some users found
unreliable for the more popular MP3 format. The format was named DivX ;-) -
complete with the smiley emoticon. Although the program was supported and
updated for a number of years by DivXNetworks (Rota's company) in summer 2001
the company released DivX 4, the first closed source commercial codec.
This codec was completely devoid of the
original Microsoft-derived code, thus finally freeing the company of
increasingly heavy legal threats from the software giant. This first release
version was considerably inferior to the MS-derived DivX 3.11, but steady
improvements in quality mean that the current implementation is one of the
highest quality and fastest MPEG-4 codecs around. The latest version 7 release
of Divx has moved away from being merely a codec and is now a fully featured
media container format. Using the .divx file extension, it allows support for a
number of DVD-like features including menus, •ubtitles in multiple languages,
chapter skip-to points, and lupport for multiple audio tracks.
Not all of these 'new' features are not
exactly new however, jnd are merely stored within riff headers within a renamed
avi ormat; only the name has changed. Naturally, conventional AVI ile types can
also still be created. For this reason DivX-encoded vlPEG-4 files still have
some limitations and larger file overheads :ompared to competing solutions.
One of the most useful things about DivX is
its wide ranging acceptance in standalone players. A great many DVD players, be
they high end or entry level, now support DivX CDs, which for the most part
allow for on-screen quality similar to DVD. The fact that the DivX codec allows
users to create high quality rips of copyrighted content means that it will
always be somewhat controversial, though users are legally allowed to download
adware-free versions from www.divx.com.
The latest version makes full use of
multi-core CPUs for increased encoding performance.
Codec: H.264/MPEG-4 AVC
H.264, also known as MPEG-4 AVC is
currently the buzz-word codec on the block, mostly thanks to support from
Apple's ubiquitous media players. It delivers quality noticeably superior to
even DivX and Xvid with similar bit rates, or equivalent quality at lower bit rates.
H.264 is also used as the codec of choice in Blu-rays and the now-defunct
HD-DVD format. It also forms the backbone of Sky HD, Freeview-HD and Virgin
Media's Tivo product. H.264/AVC/MPEG-4 Parti0 incorporates a number of new
features that allow it to compress video much more effectively than older
standards.
H.264 has relatively high software
overheads when watching at high definition resolutions. Watching an HD film
trailer for example will see older computers taxed to 100% CPU utilisation at
times, and will result in dropped frames on slower machines. Nevertheless, if
you have the hardware for it, H.264 is the best codec for storing lots of video
data at high quality. It uses less hard drive space than DivX or Xvid for the
same visual quality and has become primary choice for fans of encoding.
So what is the answer to the question
"which codec should I be using"? Hopefully you will now see that this
is all down to your usage.
If you're doing something like sending
small clips to your friends and family, then good old MPEG-1 would be ideal. If
you're looking to compress video captured to a high quality medium for
conversion to DVD or SVCD, then the more advanced MPEG-2 is the way to go.
Finally, if you are looking to store files on your PC at high video quality
without requiring too much hard drive space, an MPEG-4 based codec such as
Xvid, DivX, WMP or H.264 should be chosen, depending on the specs of your
machine and, of course, the relative convenience of the encoders on offer.
