To understand digital media formats, you have to understand the difference between container formats and codecs. Container
formats define the way data is stored within a media file or streamed
over a network. A codec is piece of software used to compress and
decompress digital media. For Windows to play back a sound or video
clip, it must be able to open the format and process its compressed
contents. As a result, you might find that some files in supported container formats can't be played back in Windows Media Player because the required codec is not available.
Windows Media Player 12
plays back media files in a long list of formats and supports many
widely used codecs. The list of supported formats includes every one
that was available in Windows Media Player 11 with Windows Vista and
Windows XP. Windows 7 adds support for some popular formats that
required third-party playback programs in previous Windows versions. Table 1 lists all of the newly supported file types.
Table 1. File Formats Newly Supported in Windows Media Player 12
| File Type | File Name Extension(s) | Description |
|---|
| 3GPP/3GPP2 Audio/Video | .3gp, .3gpp, .3g2, .3gp2 | Allows delivery and playback of multimedia over 3G wireless networks. |
| ADTS Audio | .aac | Used for streaming audio content from media players or websites in Advanced Audio Coding (AAC) or MPEG-4 Audio formats. |
| AVCHD Video | .m2t, .m2ts, .mts | High-definition video container format used by many portable video recorders. It typically uses the H.264 video compression codec (also known as MPEG-4 AVC). |
| MP4 Video | .m4v, .mp4, .mp4v | This widely used high-definition video container format typically uses H.264 video compression. |
| MPEG-2 TS Video | .ts, .tts | A streaming format used to deliver synchronized digital audio and video; commonly used in European digital TV systems. |
| MPEG-4 Audio | .m4a | Also known as Advanced Audio Coding (AAC), this is the default format used by Apple's iTunes software and online music store; files in this format that use Apple's FairPlay copy protection are not supported, nor are those that use Apple Lossless Format. |
| QuickTime Movie | .mov | A container format used by many portable video cameras. |
As you can see from this
list, the changes in Windows Media Player 12 will be especially welcome
to anyone who has purchased unprotected music from the Apple iTunes
Music Store. Files in this format can now be included in a Windows Media
Player Music library and played back alongside those in the MP3 and
Windows Media Audio (WMA) formats. In addition, Windows Media Player 12
now directly supports the most common high-definition video formats,
especially those that use the H.264 video compression codec. Finally, if
you have a digital camera that records video to a flash memory card in
the QuickTime Movie (file extension .mov) or AVCHD formats, you can now play those files directly in Windows without installing third-party software.
These improvements,
while welcome, do not begin to cover every available audio and video
format. Digital media enthusiasts in particular are likely to need
additional software to allow playback of formats that aren't supported
directly.
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A default installation of Windows Media Player includes codecs that can handle most widely used formats and is capable of downloading updated codecs
automatically. You can also download and install third-party codecs
that are designed to work with Windows Media Player but are not endorsed
or supported by Microsoft. You do so at your own risk—a buggy codec can
cause the Player to crash, freeze, or suffer reduced performance, even
when working with clips in a completely different format than the one
supported by the rogue codec.
Enthusiasts who rip and share digital video files
are the most common source of codec-related issues with Windows Media
Player. Some enthusiast sites offer so-called codec packs, which install
a collection of third-party codecs that have the potential to cause at
least as many problems as they solve. Before you install one of these
packages, we recommend that you research it extensively—and, of course,
have a backup image ready. In some cases, especially when playing
content that was encoded using an older media-authoring program, you
might decide to take the risk and install an untested codec. If you do,
be sure to set a restore point first.
The two most commonly used video codecs, both of which are frequently used in AVI files, are DivX and Xvid. Windows
Media Player 12 includes support for these codecs as part of its H.264
package. In some cases, however, files produced using these codecs are
saved in container formats that are incompatible with Windows 7; this is
the case with the Matroska
Video file type (.mkv), which requires additional software to play back
using Windows Media Player. For more information about these codecs,
along with download and installation instructions, visit the DivX website at divx.com and the Xvid home at xvid.org. If you're curious about Matroska, you'll find specifications, FAQs, and downloads at matroska.org.
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When you first run
Windows Media Player, one of the custom setup options allows you to pick
and choose which file formats will be associated with it; you can
review and change these options any time by opening the Default Programs
option from Control Panel or the Start menu, clicking Set Your Default
Programs, and choosing Windows Media Player from the list of programs.
On a clean installation
of Windows 7, the listing for Windows Media Player should say This
Program Has All Its Defaults. If you've installed any third-party media
software since installing Windows, it's possible that another program
might have taken control of some media file formats. In that case, the
Set Default Programs dialog box will look like the one shown in Figure 1. Note that four file types normally handled by Windows Media Player are now controlled by the Zune software on this computer.
To restore all default file
associations for Windows Media Player, click Set This Program As
Default. To inspect (and if necessary adjust) settings individually,
click Choose Defaults For This Program.
Popular container formats supported in Windows 7 include Advanced Systems Format files, which can contain audio, video, or both. Windows Media Audio (file name extension .wma) and Windows Media Video (.wmv) are ASF
files that have been compressed using Windows Media Audio and Windows
Media Video codecs, respectively. Files in either format can be packaged
using digital rights management and can be encoded at various levels of
quality (which in turn affects disk space used per file). The generic
.asf file name extension indicates that the file was compressed with a
different codec and that ASF is simply a "wrapper" around the actual
codec.
Windows
Media metafiles are XML files that can be created and viewed in a plain
text editor. They're typically designed to be redirectors, which allow
Windows Media Player to open and play streaming media sources on web
servers. The file name extensions typically end in x: .asx, .wax, .wvx, .wmx.
Audio Video Interleave (.avi) and QuickTime Movie
(.mov) are widely used container formats used for playback of video
clips (with or without audio tracks) on Windows-based computers. AVI is a
Microsoft-developed format, whereas QuickTime was developed by Apple. Support for QuickTime Movie files in Windows Media Player 12 is primarily designed for compatibility with portable cameras that use this format for recording. For files in this format that you encounter on the web, you might still need Apple's QuickTime Player (apple.com/quicktime).
A group of widely used
formats from the Moving Pictures Experts Group are supported in Windows
Media Player. The extremely popular MP3 audio
format is the best known. Digital media files that use this format
typically have the .mp3 file name extension and can be played back in
nearly any audio player or portable music jukebox. MPEG-2 encoded video files are DVD quality and typically use .mpeg, .mpg, .mpv, or .m2v as a file name extension.
MPEG-4 Audio, also known as Advanced Audio Coding (AAC),
evolved from the popular MP3 standard and boasts higher quality with
significantly smaller file sizes. It is the default format used with
Apple's iPod and iPhone portable music devices and the iTunes online
store. Windows Media Player plays back AAC-formatted files that use the
.m4a extension; the .m4p
extension typically means that the file is digital rights management
(DRM)–protected and will play back only in an authorized copy of Apple's
iTunes software.
For recorded TV, Windows 7 plays back files in either of two formats. Microsoft Digital Video Recording (.dvr-ms) is the file format used by the TV recording engine in older versions of Windows Media Center. Windows TV (.wtv) is the file format used by the TV recording engine included with Windows Media Center in Windows 7.
And finally: When is a media file format not a file format at all? When it's a CD
Audio track. If you open an audio CD using Windows Explorer, you'll see
each track listed as a CD Audio file, with the file name extension
.cda. These files are representations of audio tracks, and they cannot
be copied to the Windows file system in their native format or played
back except from an audio CD.
