WMV
WMV stands for Windows Media Video and is a
generic name given to a number of Microsoft-designed video codecs. Based on the
early drafts of the MPEG-4 specification, by the time initial versions were
made public it had evolved sufficiently from MPEG-4 (thanks to in-house
development) to be considered a separate codec in its own right.
Windows
Media Player 9
The initial codec has been updated over
time, and in 2003 Microsoft submitted the current variant based on its Windows
Media Player 9 technology to the Society of Motion Picture and Television
Engineers for standardisation. This codec is used frequently by companies
wishing to stream relatively high-quality video over the internet, because it's
robust and has good browser integration properties. AVI file types generally
require the whole video to be downloaded in order to begin viewing, but WMV and
MPG content can be streamed immediately so long as the internet connection is
fast enough to keep up.
One of the nice things about .wmv video is
that high quality home footage can be encoded into this efficient medium with
software freely downloadable from Microsoft's website. Users wanting to
experiment with this excellent tool should head on over to www.microsoft.com
where the latest version allows the creation of multi-pass VBR videos that
rival even the latest H.264/AVC formats for quality and compression.
MOV
If AVI, MPG and WMV files are the three
most popular file formats, MOV is surely the next most frequently encountered.
As with AVI, MOV is a wrapper file format
that can accommodate a number of codecs. Most older MOV files will use a codec
known as Sorenson. Sorenson based video files are still popular on the web, so
if you have a Windows XP based system it will only be so long before you
finally relent and download the QuickTime program so you can watch movie
trailers, video reviews and music video samples. Thankfully the latest version
of Apple's player is not quite as invasive as it used to be (if you can find
the installer that doesn't force iTunes down your throat), and it is easy to
prevent it from taking over as your machine's default player for virtually all
multimedia files.
One of the main reasons QuickTime Sorenson
is used in many movie trailers is that it is cheap to licence, works well at
internet bit rates and streams; meaning you can watch what has downloaded so
far right away rather than having to wait for the whole file - as you would
have to with AVIs. Despite its continued popularity as an online video codec,
if you are looking to store your own videos at high quality on your PC,
Sorenson is a poor choice. Compared to MPEG-2, MPEG-4 implementations such as
DivX or the latest Microsoft codecs, it simply does not offer the flexibility,
nor the quality.
In 1998 the ISO announced that the
QuickTime .mov file format would be used as the basis of the Mpeg-4 (.mp4)
container standard. MPEG-4 video encoded using early versions of QuickTime
(version 6.x) and using the .mov file format compare extremely unfavourably
compared to DivX and Xvid. This is because QuickTime could only encode and
decode using Simple Profile (SP). The advanced (ASP) features of the codec such
as B-frames are unsupported, though support has fortunately been added for
QuickTime 7's H.264 encoder, making it a far more attractive option for making
high quality video than previous QuickTime MPEG-4 encoders.
MKV
MKV
is the Matroska Multimedia Container
The Matroska Multimedia Container is an
open source and royalty free container format, that can hold an unlimited
number of video, audio, picture or subtitle tracks in one file. MKV files are
among the most common file formats used by rippers of high definition content,
as it overcomes many of the limitations of AVI. You'll often see people
complaining about the usage of MKV files, but once you have a suitable player
its advantages are numerous. AVI does not provide a standardized way to encode
aspect ratio information, with the result that players cannot select the right
one automatically; it was not intended to contain video using any compression
technique which requires access to future video frame data beyond the current
frame, and cannot contain some specific types of variable bitrate (VBR) data
reliably. Each of these limitations are circumvented by MKV, explaining its
increasingly prevalent use.
