moving picturestmyn1 moving pictures mpeg, motion picture experts group mpeg is a set of standards...

Moving Pictures tMyn 1

Moving Pictures

• MPEG, Motion Picture Experts Group

• MPEG is a set of standards designed to support ”Coding of Moving Pictures and Associated Audio – for digital storage media at up to 1.5 Mbits/s”.

• MPEG-1 (Nov 1992) was designed to permit full motion video recordings on CD players originally designed for stereo audio playback.


• MPEG-2 or ITU-T-recommendation H.262, Generic Coding of Moving Pictures and Associated Audio (Nov 1994), addressed greater input-output format flexibility, data rates, and system considerations such as transport and synchronization, topics neglected in MPEG-1.

• MPEG-2 supports variations of Digital TV.• The following section describes the basic theory of

operation of the simplest version of MPEG-2:


• MPEG compresses a sequence of moving images by taking advantage of the high correlation that exists between successive pictures of a moving picture.

• MPEG constructs three types of pictures: Intra pictures (I-pictures), Predicted pictures (P-pictures), and Bi-directional Prediction pictures (B-pictures).

• In MPEG, every M-th picture in a sequence can be fully compressed using a standard JPEG algorithm; these are the I-pictures.

• The process then compares successive I-pictures and identifies portions of the image that have moved.


• The image sections that didn’t move are carried forward in time to intermediate pictures by the decoder memory.

• The process then selects a subset of intermediate pictures, then predicts (via linear interpolation between I-pictures) and corrects the location of the image sections that were found to have moved.

• These predicted and corrected images are the P-pictures.

• The pictures between the I- and P-pictures are the B-pictures that incorporate the stationary image sections uncovered by moving sections.

• The I-pictures are compressed as if they were JPEG images.


• MPEG-4 is a patented collection of methods defining compression of audio and visual (AV) digital data. It was introduced in late 1998.

• Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications.

• 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 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for externally-specified Digital Rights Management and various types of interactivity. AAC (Advanced Audio Codec) was standardized as an adjunct to MPEG-2 (as Part 7) 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 "part" level compatibility they are referring to. The key parts to be aware of are MPEG-4 part 2 (including Advanced Simple Profile, used by codecs such as DivX, Xvid and Nero Digital) and MPEG-4 part 10 (MPEG-4 AVC/H.264 or Advanced Video Coding, used by the x264 codec, by Nero Digital AVC, and by next-gen video medium formats like Blu-ray Disc).


• Most of the features included in MPEG-4 are left to individual developers to decide whether to implement them. This means that there are probably no complete implementations of the entire MPEG-4 set of standards. To deal with this, the standard includes the concept of "profiles" and "levels", 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 scope was later expanded to be much more of a multimedia coding standard. MPEG-4 is efficient across a variety of bit-rates ranging from a few kilobits per second to tens of megabits per second. MPEG-4 provides the following functionalities:

– Improved coding efficiency

– Ability to encode mixed media data (video, audio, speech)

– Error resilience to enable robust transmission

– Ability to interact with the audio-visual scene generated at the receiver


• The H.264/MPEG-4 AVC standard includes for example the following sets of capabilities, which are referred to as profiles, targeting specific classes of applications:

• Constrained Baseline Profile (CBP) • Primarily for low-cost applications this profile is used

widely in videoconferencing and mobile applications. It corresponds to the subset of features that are in common between the Baseline, Main, and High Profiles described below.


• Baseline Profile (BP)

• Primarily for low-cost applications that requires additional error robustness, while this profile is used rarely in videoconferencing and mobile applications, it does add additional error resilience tools to the Constrained Baseline Profile. The importance of this profile is fading after the Constrained Baseline Profile has been defined.

• Main Profile (MP)

• Originally intended as the mainstream consumer profile for broadcast and storage applications, the importance of this profile faded when the High profile was developed for those applications.


• Extended Profile (XP)

• Intended as the streaming video profile, this profile has relatively high compression capability and some extra tricks for robustness to data losses and server stream switching.

• High Profile (HiP)

• The primary profile for broadcast and disc storage applications, particularly for high-definition television applications (this is the profile adopted into HD DVD and Blu-ray Disc, for example).


• High 10 Profile (Hi10P) • Going beyond today's mainstream consumer product

capabilities, this profile builds on top of the High Profile, adding support for up to 10 bits per sample of decoded picture precision.

• High 4:2:2 Profile (Hi422P) • Primarily targeting professional applications that use

interlaced video, this profile builds on top of the High 10 Profile, adding support for the 4:2:2 chroma subsampling format while using up to 10 bits per sample of decoded picture precision.


• High 4:4:4 Predictive Profile (Hi444PP)

• This profile builds on top of the High 4:2:2 Profile, supporting up to 4:4:4 chroma sampling, up to 14 bits per sample, and additionally supporting efficient lossless region coding and the coding of each picture as three separate color planes.

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