MPEG-4 video has become rather popular recently and millions of video enthusiasts worldwide encode their home video with MPEG-4 compatible video codecs. Xvid permits the creation of MPEG-4 compliant video and has received wide-spread adoption in applications and among users due to its open-source nature and unrivalled picture quality it provides.
The MPEG-4 standard defines many different coding tools and compression features. The Xvid codec supports many such features, including also more advanced features like e.g. quarterpel motion compensation. Many other popular MPEG-4 encoders support just less MPEG-4 features than Xvid and especially often lack the more demanding advanced features.
A similar situation can be observed for hardware playback devices like DVD players, portable media players or mobile phones. Most devices do not support the more demanding MPEG-4 coding tools and hence provide just very limited compatibility to Xvid.
To enable a distinction between devices with poor and those with excellent Xvid support, the Xvid certification program has been established. It defines interoperability profiles for different use-cases and ensures compatibility of hardware playback devices to the Xvid video codec. Devices marked with one of the Xvid profile logos have been verified to conform to the respective Xvid profile and provide excellent compatibility to Xvid or any other popular MPEG-4 based video codec.
In order to facilitate the creation of video targeted for different applications and playback devices interoperability profiles have been introduced to Xvid. The profiles cover all the features typically employed in the respective application scenario and feature many advanced coding tools like quarterpel motion compensation or custom quantization matrix (CQM).
Four main profiles are defined that differ with regard to supported coding tools and allowed maximum image resolutions:
- The Xvid mobile profile is least demanding and permits the creation of video for devices with smaller displays like mobile phones.
- The Xvid portable profile is targeted towards use with portable media player devices or web tablets and supports video up to VGA resolution.
- The Xvid home profile is designed for use with home video devices and set-top boxes up to PAL/D1 resolutions.
- The Xvid highdef profile has been defined for video compression at HD resolutions.
|Max Bitrate||1 334 850||4 854 000||9 708 400||20 480 000|
|Quantization method||H.263/ MPEG/ CQM||H.263/ MPEG/ CQM||H.263/ MPEG/ CQM||H.263/ MPEG/ CQM|
|Pixel Aspect Ratio (PAR)||1:1||1:1, 4:3, 16:9||1:1, 4:3, 16:9||1:1, 4:3, 16:9|
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