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Also known as Dolby Digital, it's a digital audio
format from Dolby Labs™. It can support up to 5.1 channels
of audio.
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Initially known as Audio Coding 3 AC3 is a synonym for Dolby Digital
these days. Dolby Digital is an advanced audio compression technology
allowing to encode up to 6 separate channels at bitrates up to 448kbit/s.
For more information please check out the Dolby website.
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Audio Video Interleave. The video format most commonly
used on Windows PCs. It defines how video and audio are attached
to each other, without specifying a codec.
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AVI stands for Audio Video Interleave. AVI
is a file format, like MP3 or JPG. But unlike these formats, AVI
is a container format, meaning it can contain video/audio compressed
using many different combinations of codecs. So while MP3 and JPG
can only contain a certain kind of compression (MPEG Audio Layer
3 and JPEG), AVI can contain many different kinds of compression
(eg. DivX video + WMA audio or Indeo video + PCM audio), as long
as a codec is available for encoding/decoding. AVI all look the
same on the "outside", but on the "inside",
they may be completely different.
Next time you see a video clip on your PC, there's a good chance
that it's an AVI file. AVI is the file format used by Video for
Windows, one of three video technologies used on personal computers.
(The others are MPEG and QuickTime.) In AVI, picture and sound elements
are stored in alternate interleaved chunks in the file.
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COder/DECoder. It is a small piece of software that
allows you to make/play movie/audio compressed in a certain format.
MPEG-1, MPEG-2, MPEG-4, DivX are all codecs.
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COder/DECoder. A codec is
a piece of software that allows you to encode something - usually
audio or video - to a specific format and can decode media encoded
in this specific format again. Popular Codecs: MPEG1, MPEG2, MPEG-4,
Indeo, etc. AVI, ASF, etc is not a codec but a format - that can
be encoded using different codecs.
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Lots of Video Formats like AVI can contain different
Video- and Audio-Codecs plus different information as subtitles
– The construct to contain this data is calle Container
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A container is, like the name
says, a construct to contain data - in this case video and audio
date and possibly subtitles and navigational information. For instance,
you would like to put a soundless video stream and the audio track
together in one file. To do that you need a container format. Examples
of container formats are: AVI, ASF, OGM, Quicktime, VOB and MPG.
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DivX is a video encoding format based on the MPEG-4
video compression standard, developed by DivXNetworks in conjunction
with open source developers. It can achieve a higher compression
ratio than the older MPEG-2 standard, resulting in lower bitrates
and smaller file sizes.
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There are 2 flavors of DivX
today: DivX ;) is the name of the hacked Microsoft MPEG4 codecs
(Windows Media Video V3). Those codecs were developed by Microsoft
for use in its proprietary Windows Media architecture and initially
supported encoding AVIs and ASFs but all non-beta versions included
an AVI lock, making it impossible to use them to encode to the AVI
format - and only a few tools support ASF today. What the makers
of DivX did is remove that AVI lock making it possible to encode
to AVI again, and changed the name to DivX video in order to prevent
confusion of codecs, since it's possible to have both the unhacked
and hacked codecs on the same computer if you use the Windows Media
Encoder. The latest releases of DivX also include a hacked Windows
Media Audio Codec called DivX audio - the hack of that codec is
not perfect yet and its use is limited for higher bitrates. This
codec is also known as DivX3.
The other DivX is a brand-new MPEG-4 video codec developed by DivXNetworks.
It offers much advanced encoding controls and 2 pass encoding. Furthermore
the codec can play the old DivX ;) (DivX3) movies. The codec is
commonly called DivX4.
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MPEG4 should become the next standard in digital video.
Mainly for picture phones, streaming media on the Internet and more
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MPEG means Motion Picture
Expert Group and it's THE resource for video formats in general.
This group defines standards in digital video, among it the MPEG1
standard (used in Video CDs), the MPEG2 standard (used on DVDs and
SVCDs), the MPEG4 standard and several audio standards - among them
MP3 and AAC. Files containing MPEG-1 or MPEG-2 video often use either
the .mpg or .mpeg extension. A group working under the directives
of the International Standards Organisation (ISO) and the International
Electro-Technical Commission (IEC).
The groups work concentrates on defining standards for the coding
of moving pictures, audio and related data.
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MPEG4 should become the next standard in digital video.
Mainly for picture phones, streaming media on the Internet and more
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MPEG-4 is a standard defined
by the Working Group 11 (Moving Picture Expert Group) of ISO (International
Standard Organization) in October 1998 (date of the first draft
of the standard). It is the standard for the mature digital era.
With its added features, MPEG-4 offers better compression, interactivity,
and universal Internet/wireless access to the medium.
MPEG4 is pretty much a collection of standards defined by the MPEG
Group, and it should become the next standard in digital video (mainly
for picture phones, streaming media on the Internet and more). MPEG4
allows the use of different encoding methods, for instance a keyframe
can be encoded using ICT or Wavelets resulting in different output
qualities.
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Compression used on DVDs.
Finalized in 1996, MPEG2 is a major improvement compared to MPEG-1.
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MPEG is a standard for compressing
sound and movie files into an attractive format for downloading--or
even streaming--across the Internet. The MPEG-1 standard streams
video and sound data at 150 kilobytes per second--the same rate
as a single-speed CD-ROM drive--which it manages by taking key frames
of video and filling only the areas that change between the frames.
Unfortunately, MPEG-1 produces only adequate quality video, far
below that of standard TV.
MPEG-1 defines a framework for coding moving
MPEG-2 compression improves things dramatically. With MPEG-2, a
properly compressed video can be shown at near-laserdisc clarity
with a CD-quality stereo soundtrack. For that reason, modern video
delivery mediums, such as digital satellite services and DVD, use
MPEG-2.
MPEG video - Video compressed according to the MPEG encoding system.
MPEG-1 is typically used for low data rate video such as on a Video
CD. MPEG-2 is used for higher-quality video, especially interlaced
video, such as on DVD or HDTV.
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A digital music format, similar to MP3.
Ogg Vorbis is open source and suspected to be the most powerful
successor of MP3.
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Ogg Vorbis is an open-source
digital music format, similar to MP3. Unlike MP3, however, Ogg Vorbis
encoders, decoders, and plug-ins are developed under the GPL (GNU
Public License) and can be distributed freely. The most popular
MP3 players support Ogg Vorbis that is suspected to be the most
powerful
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OGM can be used as an alternative to the AVI container
and it can contain Ogg Vorbis, MP3 and AC3 audio, all kinds of video
formats, chapter information and subtitles
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OGM stands for OGg Media which
is the name of the Ogg container implementation by Tobias Waldvogel.
OGM can be used as an alternative to the AVI container and it can
contain Ogg Vorbis, MP3 and AC3 audio, all kinds of video formats,
chapter information and subtitles
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