MP4

MPEG-4 is a patented collection of method defining compression of audio and visual (AV) digital data. It was introduced in late 1998 abs designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO Moving picture Experts Groups under the formal standard ISO14496-coding of audio-visual objects.Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice(telephone, videophone) and broadcast television application.

MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2 and other related standards, adding new features such as (extended) VRML support for 3Drendering, object-oriented composite files(including audio, video and VRML objects), support for externally speckfied Digital Rights Management and various types of interactivity. AAC (Advanced Audio Coding) was standardized as an adjunct to MPEG-2 before MPEG-4 was issued.

MPEG-4 is still a developing standard and is divided into a number of parts.Companies promoting MPEG-4 compatibility do not always clearly state which "parts level compatibility they are referring to. The key parts to be aware of are MPEG-4 part 2 and MPEG-4 part 10.

Most of the features included in MPEG-4 are left to individual developer to decide whether to implement them. This means that there are probably mo complete implementations of the entire MPEG-4 Ste of standards. To deal with this,that standard includes the concept of "profiles" and "leaves" , allowing a specific set of capabilities to be defined in a manner appropriate for a subset of applications.

Initially, MPEG-4 was aimed primarily at low bit-rate video communications;however, its scopes as a multimedia coding standard was later expanded. MPEG-4 is efficient across a variety of bit-rates ranging from a few kilobits per second to tens of megabits per second.