MPEG-4 Part 2, MPEG-4 Visual (formally ISO/IEC 14496-2) is a video compression format developed by MPEG with a number of companies, primarily Mitsubishi Electric, Hitachi and Panasonic. It belongs to the MPEG-4 ISO/IEC standards. It is a discrete cosine transform compression standard, similar to previous standards such as MPEG-1 Part 2 and H.262/MPEG-2 Part 2.
MPEG-4 Part 2 is H.263 compatible in the sense that a basic H.263 bitstream is correctly decoded by an MPEG-4 Video decoder. (MPEG-4 Video decoder is natively capable of decoding a basic form of H.263.) In MPEG-4 Visual, there are two types of video object layers: the video object layer that provides full MPEG-4 functionality, and a reduced functionality video object layer, the video object layer with short headers (which provides bitstream compatibility with base-line H.263). MPEG-4 Part 2 is partially based on ITU-T H.263. The first MPEG-4 Video Verification Model (simulation and test model) used ITU-T H.263 coding tools together with shape coding.
The MPEG-4 Visual format was jointly developed by more than a dozen organizations from across the world, with their patent contributions listed by MPEG LA in a patent pool. The majority of company patent contributions towards the development of the MPEG-4 Visual format came from three companies: Mitsubishi Electric (255 patents), Hitachi (206 patents), and Panasonic (200 patents). See Patent holders below for a full list of patent holders.
To address various applications ranging from low-quality, low-resolution surveillance cameras to high definition TV broadcasting and DVDs, many video standards group features into profiles and levels. MPEG-4 Part 2 has approximately 21 profiles, including profiles called Simple, Advanced Simple, Main, Core, Advanced Coding Efficiency, Advanced Real Time Simple, etc. The most commonly deployed profiles are Advanced Simple and Simple, which is a subset of Advanced Simple.
Most of the video compression schemes standardize the bitstream (and thus the decoder) leaving the encoder design to the individual implementations. Therefore, implementations for a particular profile (such as DivX or Nero Digital which are implementations of Advanced Simple Profile and Xvid that implements both profiles) are all technically identical on the decoder side. A point of comparison would be that an MP3 file can be played in any MP3 player, whether it was created through iTunes, Windows Media Player, LAME or the common Fraunhofer encoder.
Advanced Simple Profile's notable technical features relative to the Simple Profile, which is roughly similar to H.263, include:
The quarter-pixel motion compensation feature of ASP was innovative, and was later also included (in somewhat different forms) in MPEG-4 Part 10 and VC-1. Some implementations omit support for this feature, because it has a significantly harmful effect on speed and it is not always beneficial for quality.
The global motion compensation feature is not actually supported in most implementations although the standard officially requires decoders to support it. Most encoders do not support it either, and some experts say that it does not ordinarily provide any benefit in compression. When used, ASP's global motion compensation has a large unfavorable impact on speed and adds considerable complexity to the implementation.
|Level||Max bit depth and
and frame rate
|Max data rate|
|2||10-bit 4:2:2||1920×1080 30p/30i||600|
|3||12-bit 4:4:4||1920×1080 30p/30i||900|
|4||12-bit 4:4:4||2K×2K 30p||1,350|
|5||12-bit 4:4:4||4K×2K 30p||1,800|
|6||12-bit 4:4:4||4K×2K 60p||3,600|
|Sun Patent Trust||125|
|Robert Bosch GmbH||27|
|Nippon Telegraph and Telephone||24|
|GE Technology Development||23|
|Cable Television Laboratories, Inc.||1|
|Oki Electric Industry||1|
MPEG-4 Part 2 has drawn some industry criticism. FFmpeg's maintainer Michael Niedermayer has criticised MPEG-4 for lacking an in-loop deblocking filter, GMC being too computationally intensive, and OBMC being defined but not allowed in any profiles among other things. Microsoft's Ben Waggoner states "Microsoft (well before my time) went down the codec standard route before with MPEG-4 part 2, which turns out to be a profound disappointment across the industry - it didn't offer that much of a compression advantage over MPEG-2, and the protracted license agreement discussions scared off a lot of adoption. I was involved in many digital media projects that wouldn't even touch MPEG-4 in the late 1990s to early 2000s because there was going to be a 'content fee' that hadn't been fully defined yet."