Supported Media File Types; Digital Media Formats: Codecs Versus File Containers - HP SL4778N Manual De Instrucciones

Supported Media File Types

Digital media formats: Codecs
versus file containers
Despite international efforts to create standard-based
audio and video formats, many format types are
incompatible.
The Codec (compressor and decompressor) is the
method used to compress and decompress digital
media files. Audio/video streams usually incorporate
two separate codecs: one for the compressed video
and one for the compressed audio. The MPEG codecs
include profiles and levels, which are the minimum
processing requirements for a compliant decoder.
Examples of codecs are:
JPEG: Used by almost all digital cameras to
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compress digital images.
MPEG-1, MPEG-2, and MPEG-4: Audio and video
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codecs developed by International Standards
Technical committees.
VC-1: A video codec developed by Microsoft.
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Dolby Digital: An audio codec used in DVD
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movies and in high-definition broadcasting.
The File container is the type of file that the digital
bit stream is stored in, regardless of the codec used.
File containers have a specific structure, which helps
decoders identify the codecs necessary for playback.
File containers may support multiple codecs, and may
also include media metadata, DRM (digital rights
management) keys, and other stream-related
parameters. Examples of file containers are:
AVI (.avi)
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Quicktime (.mov)
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MP4 (.mp4)
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WMV (.wmv)
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DivX (.divx)
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Mpeg (.mpg)
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Popular codecs
MPEG codecs. The Motion Pictures Experts
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Group (MPEG) has developed a variety of A/V
codecs, including:
MPEG-1, which is used in VCD movies.
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MPEG-2, which includes the audio codecs
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MPEG-2 Layer II (MP2) and MPEG-2 Layer III
(MP3), and which is used in DVDs, in HDTV,
and in many movie download services.
MPEG-4, part 2, which is the basis for DivX,
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Xvid, and other low bit-rate codecs.
MPEG-4, part 10, or H.264, or Advanced
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Video Codec (AVC), which is the basis for
HD-DVD and Blu-ray formats. It is also the
default video codec in iTunes.
AAC (Advanced Audio Codec, also known as
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MPEG-2, part 7, or MPEG-4, part 3), is the
default audio codec in iTunes.
With MPEG-2, MPEG introduced for the first time
the concept of profiles and levels. Profiles and
levels define the minimum processing
requirements for a compliant decoder. For
example:
DVD movies use MPEG-2 at Main profile and
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Main Level (or MPEG-2 MP@ML).
HDTV uses a subset of Main profile at High
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Level (MP@HL).
Two of the most common profiles for MPEG-4,
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part 2, are the Simple Profile (SP) and the
Advanced Simple Profile (ASP).
Windows Media Codecs. Microsoft has
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developed a number of codecs, including:
WMV7 and WMV8, which are early versions
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of the Microsoft video codec.
WMV9, which is the current version of the
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Microsoft video codec.
VC-1, which is the Advanced Profile of the
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WMV9 codec, and which is needed for
support by both Blu-ray and HD-DVD players.
WMA (Windows Media Audio), including
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WMA Pro, which is a multi-channel audio
codec.
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Specifications