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C h a p t e r 7 Understanding Audio/Video Technology 75

File Format Extension Characteristics
MPEG-4 .mpg, .mp4
Most recent version of the MPEG format, optimized
MPEG-PS .mpg, .mpeg for both high definition and Internet video; used in
QuickTime most newer digital camcorders; the H.264 and DivX
RealVideo .mov, .qt codecs build on and extend basic MPEG-4
.rm, .rv compression
WebM
.webm PS stands for “program stream;” this is a streaming
Windows Media video format used with some MPEG-1 and MPEG-2
Video (WMV) .wmv files
Xvid .xvid
Apple’s proprietary audio/video format; works with
both Mac OS and Windows

Media file format used by RealPlayer; the RealMedia
format (RM) can contain either audio or video files; a
heavily compressed format that results in lower-
quality video than with other competing formats

One of the newest video file formats, designed for
royalty-free open-source storage; designed for use
with HTML5 video; supported by Google/YouTube,
Mozilla, and Opera

Microsoft’s proprietary digital video file format,
playable with Windows Media Player; offers twice the
bit rate of comparable MPEG-4 files

Another variation of the MPEG-4 format, similar to
the competing DivX codec

Note

A container format is a file format that holds different types of data within
the file. These formats, such as the Audio Video Interleave (AVI) and
RealVideo formats, contain not only the underlying audio and video, but
also metadata about the source material—chapter information, subtitles,
and such.

Choosing the Right Format for Your YouTube Videos

All the technicalities out of the way, it’s time to decide what formats to use when
creating your YouTube videos. Now, you might think this is somewhat academic, as
YouTube stores and serves its videos in a single format—Adobe’s Flash Video (FLV)
format, using H.264 compression. Whatever format you upload, YouTube will con-
vert your videos to this format after you upload them.