Codec Containers
The type of codec container for a multimedia file stream can generally be detected by its extension. Codec containers are wrappers around the video file that specify the metadata pertaining to the video file and the codec format it uses. The assortment of codec containers in use today reflects the need of the specific platform on which the media is played (e.g., 3GP container formats for mobile phones) and the prescription of various media companies on how meta-data ought to be formatted in the media file or stream (QuickTime video container from Apple and ASF container format from Microsoft).
Some of the commonly used container formats are described below.
MPEG-4 Part 14 (MP4)
MPEG-4 Part 14 refers to the container format standard defined under the MPEG-4 standard, commonly known as MP4. Almost any kind of data can be supported by the MP4 container format using private streams. MP4 containers store audio and video stream and meta-data, such as subtitles and other information, and allow streaming of media files over an IP network.
Filenames using the MP4 standards have the extension .mp4. The .m4a also is used if the file or stream only contains an audio stream.
3GP
The 3GP is a simplified version of the MPEG-4 Part 14 (MPE4) container format defined by the Third Generation Partnership Project (3GPP) for use on 3G mobile phones. Although primarily designed for 3G phones, it can also be used on 2G and 2.5G phones.
3G supports subtitles in 3GPP Timed Text (a variation of MPEG-4 Part 17) format but does not support other meta-data supported by MP4. File extensions are .3gp (for GSM phones) and .3gp2 (for CDMA phones).
Advanced Systems Format (ASF)
Advanced Systems Format is Microsoft’s proprietary container format that was specially designed to provide seamless support for streaming over the IP, HTTP and from local disks. It provides support for any audio and video codec formats and supports meta-data such as subtitles, album information, etc. It also provides the framework for DRM protection in Windows Media Audio (WMA) and Windows Media Video (WMV) files.
Typical file extensions for ASF are .asf, .wma, .wmv.
Flash Video
The Flash Video format was initially developed by Macromedia to deliver video over the Internet using the Macromedia Flash Player (now Adobe Flash Player). Until version 9 update 2, it used to support only Sorensen Spark and On2’s VP6 codec formats. Adobe Flash Player Version 9 update 2 provides support for H.264 and MPEG-4 ASP.
Typical file extensions for Flash video are .flv, .f4v (Video for Flash Player), .f4p (Protected video for Flash Player), .f4a (Audio for Flash Player), .f4b (Audio Book for Flash Player).
QuickTime format
The QuickTime format was developed by Apple. It was the ISO-approved standard as the base for creating MPEG-4 Part 14 container format. Hence several features in the two formats are congruous with each other. It also has special features that make it possible to edit media in place without making a copy of the media.
Typical file formats for this container are .qt and .mov.
NEXT: Choosing an appropriate video codec
Page 5: next page
