Video
Formats
This software supports extracting audio from these video formats:
| Format |
Description |
| AVI
(DivX, XviD, MPEG-4, Uncompressed, Cinepak) |
AVI stands for Audio Video Interleave. It is a special
case of the RIFF (Resource Interchange File Format). AVI is defined
by Microsoft. AVI is the most common format for audio/video data
on the PC. AVI is an example of a de facto (by fact) standard. AVI
Files are a special case of RIFF files. RIFF is the Resource Interchange
File Format. This is a general purpose format for exchanging multimedia
data types that was defined by Microsoft and IBM during their
long forgotten alliance.
|
| MPEG
(MPEG-1, MPEG-2 Video) |
MPEG is both a file format and a codec for digital
video. There are actually three forms of MPEG: MPEG video, for picture
only; MPEG audio, which is discussed in the previous section; and
MPEG systems, which includes both audio and video tracks.
MPEG files provide excellent picture quality but can be very
slow to decompress. For this reason, many MPEG decoding systems
are hardware-assisted, meaning that you need a board to play MPEG
files reliably without dropping a lot of frames. Although software
decoders definitely exist (and there are some very good ones out
there), they tend to require a lot of processor power on your
system and also usually support MPEG video only (they have no
soundtrack).
A third drawback of MPEG video as a standard for the Web is that
MPEG movies are very expensive to encode. You need a hardware
encoder to do so, and the price ranges for encoders are in the
thousands of dollars. As MPEG becomes more popular, those prices
are likely to drop. But for now, unless you already have access
to the encoding equipment or you're really serious about your
digital video, a software-based format is probably the better
way to go. |
| WMV |
Windows Media Video.
Formerly known as .ASF file format from Microsoft.
A .WMV file includes a video stream (compressed using MS MPEG4 or
WMV1 codec) combined with WMA encoded audio stream. The file format
is proprietary and backward incompatible. Currently, dedicated to
slow dialup connections, this media format does not allow even sub-VHS
video quality due to blurred picture. WMA audio quality, compared
to MPEG Layer3 of the same bitrate, isn't better either.
You may wish to use Windows Media format to create smallest files
that are suitable to send by e-mail, however you must keep in mind
that .WMV file works like "one way ticket" - once created,
it can't be edited anymore, without horrific quality loss. As opposite,
AVI files compressed with MPEG4 video codec are still editable and
often it is possible to retain source video quality. |
| Quick Time |
Apple video format for the Macintosh, read only.
Although QuickTime was developed by Apple for the Macintosh, QuickTime
files are the closest thing the Web has to a standard cross-platform
movie format (with MPEG a close second). The Apple system software
includes QuickTime and a simple player (called MoviePlayer or SimplePlayer).
For PCs, QuickTime files can be played through the QuickTime for
Windows (QTfW) package, and the freely available Xanim program will
play them under the X Window System and UNIX. QuickTime movies have
the extension .qt or .mov.
QuickTime supports many different codecs, particularly CinePak
and Indeo, both of which can be used cross-platform. See the "Codec
Formats" section later in this chapter for more information
on these formats.
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