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Video Formats
Encoding
Encoding is the process of changing data from one form into another according to
a set of rules specified by a codec. The data is usually a file containing
audio, video or still image. Often the encoding is done to make a file
compatible with specific hardware (such as a DVD Player) or to compress or
reduce the space the data occupies.
Common video encoding methods are DivX, MPEG-1, MPEG-2 and MPEG-4.
A common audio encoding method is MP3 although many others exist
including MPEG1 audio, DTS, and Dolby Digital
DivX
DivX™ is a new format for digital video, much like MP3 is a format for
digital music. DivX™ is the brand name of a patent-pending video compression
technology created by DivXNetworks, Inc., (also known as Project Mayo). The DivX™
codec is based on the MPEG-4 compression standard. This codec is
so advanced that it can reduce an MPEG-2 video (the same format used for
DVD or Pay-Per-View) to ten percent of its original size.
DivX.com.
MPEG-1
An ISO/IEC (International Organization for Standardization/ International
Electrotechnical Commission) standard for medium quality and medium bitrate
video and audio compression. It allows video to be compressed by the ratios in
the range of 50:1 to 100:1, depending on image sequence type and desired
quality. The encoded data rate is targeted at 1.5Mb/s - this was a
reasonable transfer rate of a double-speed CD-ROM player (including audio and
video). VHS-quality playback is expected from this level of compression. The
Motion Picture Expert Group (MPEG) also established the MPEG-2 standard
for high-quality video playback at a higher data rates. MPEG-1 is used in
encoding video for VCD.
MPEG FAQ
MPEG-2
An encoding standard designed as an extension of the MPEG-1
international standard for digital compression of audio and video signals.
MPEG-1 was designed to code progressively scanned video at bit rates up to about
1.5 Mbit/s for applications such as CD-i. MPEG-2 is directed at broadcast
formats at higher data rates; it provides increased support for efficiently
coding interlaced video, supports a wide range of bit rates and provides for
multichannel surround sound coding such as PCM, Dolby Digital, DTS
and MPEG audio.
MPEG-3
A proposed variant of the MPEG video and audio compression algorithm and file
format. MPEG-3 was intended as an extension of MPEG-2 to cater for HDTV
but was eventually merged into MPEG-2.
MPEG-3 should not be confused with MP3 which is MPEG-1 layer 3 popularly
used for audio encoding.
MPEG-4
An ISO/IEC standard 14496 developed by the Moving Picture Experts Group (MPEG),
the committee that also developed MPEG-1 and MPEG-2. These
standards made interactive video on CD-ROM, DVD and Digital Television
possible. MPEG-4 is the result of another international effort involving
hundreds of researchers and engineers from all over the world. MPEG-4 was
finalized in October 1998 and became an International Standard in 1999. The
fully backward compatible extensions under the title of MPEG-4 Version 2 were
frozen at the end of 1999, to acquire the formal International Standard Status
early in 2000. Several extensions were added since and work on some specific
work-items is still in progress.
MPEG-4 builds on the proven success of three fields:
>Digital television
>Interactive graphics applications (synthetic content)
>Interactive multimedia (World Wide Web, distribution of and access to content)
For more detailed information visit
www.videohelp.com
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