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Multimedia Systems

Multimedia Systems. Lecture - 12. OUTLINE. MPEG Standards (continued). MPEG Overview ( Recap ). MPEG is the name of a family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format.

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Multimedia Systems

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  1. Multimedia Systems Lecture - 12

  2. OUTLINE • MPEG Standards (continued)

  3. MPEG Overview (Recap) • MPEG is the name of a family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format. • As compared to other video and audio coding formats, MPEG files are much smaller for the same quality. • MPEG standards include MPEG-1, MPEG-2, MPEG-3, MPEG-7, and so on.

  4. MPEG-2 • MPEG-2 is broader in scope and wider in appeal as compared to its predecessor. • It supports higher video quality and higher data rate (up to 80 Mbits/sec) • MPEG-2 is widely used as the format for over-the-air digital television signals broadcasting, cable TV, and digital satellite TV systems.

  5. MPEG-2 • It also specifies the format of movies and other programs that are distributed on DVD and similar discs (e.g., Blu-ray discs). • It supports interlacing and high definition.

  6. MPEG-2 Parts • MPEG-2 standard was published as Parts of ISO/IEC 13818. • Part 1 • Systems – describes synchronization (timing info) and multiplexing of video and audio • Part 2 • Video – specifies compression codec for interlaced and non-interlaced video signals (Also known as H.262). • Part 3 • Audio – specifies compression codec for perceptual coding of audio signals. • Also called MPEG-2 BC; backward compatible with MPEG-1 audio decoders • Other Parts include Part 4, 5, 6, 7, 9, 10, 11. Part 8 was withdrawn.

  7. MPEG-2 Frame Types • MPEG-2 specifies that the raw frames be compressed into three kinds of frames: • intra-coded frames (I-frame), • predictive-coded frames (P-frames), and • bidirectionally-predictive-coded frames (B-frames).

  8. MPEG-2 Frame Types • An I-frame is a compressed version of a single uncompressed (raw) frame. It takes advantage of spatial redundancy and of the inability of the eye to detect certain changes in the image. • P-frames provide more compression than I-frames because they take advantage of the data in a previous I-frame or P-frame (a reference frame).

  9. MPEG-2 Frame Types • B-frames’ processing is similar to that of P-frames except that B-frames use the picture in a subsequent reference frame as well as the picture in a preceding reference frame. As a result, B-frames usually provide more compression than P-frames.

  10. MPEG-2 Typical frame sizes • I-frame: 400,000 bits • P-frame: 200,000 bits • B-frame: 80,000 bits

  11. MPEG-2 Profiles & Levels • MPEG-2 video supports a wide range of applications from mobile to high quality HD editing. • For many applications, it is not feasible to support the entire standard. To allow such applications to support only subsets of it, the standard defines profiles and levels. • Profile defines the subset of features such as compression algorithm, chroma format, etc. • Level defines the subset of quantitative capabilities such as maximum bit rate, maximum frame size, etc.

  12. MPEG-2 Profiles & Levels • A MPEG application specifies the capabilities in terms of profile and level. • For example, a DVD player may say it supports up to main profile and main level (often written as MP@ML). • It means the player can play back any MPEG stream encoded as MP@ML or less.

  13. Various MPEG-2 Profiles & Levels • Profiles • Simple profile (SP) • Main profile (MP) • SNR Scalable profile (SNR) • Spatially Scalable profile (Spatial) • High Profile (HP) • Levels • Low Level (LL) • Main Level (ML) • High 1440 (H-14) • High Level (HL)

  14. Various MPEG-2 Profiles & Levels • Constraints on levels: • High • 1920 samples/line (horizontal resolution) • 1152 lines/frame (vertical resolution) • 60 frames/sec • 80 Mbits/s • High 1140 • 1440 samples/line • 1152 lines/frame • 60 frames/sec • 60 Mbits/s

  15. Various MPEG-2 Profiles & Levels • Main • 720 samples/line • 576 lines/frame • 30 frames/sec • 15 Mbits/s • Low • 352 samples/line • 288 lines/frame • 30 frames/sec • 4 Mbits/s

  16. MPEG-3 • MPEG-3 dealt with standardizing scalable and multi-resolution compression. • Targeted HDTV applications with sampling dimensions up to 1920 x 1080 x 30 Hz and coded bitrates between 20 and 40 Mbit/sec • MPEG-2 was found to scale to these • dimensions, so MPEG-3 was dropped/ merged with MPEG-2.

  17. MPEG-4 • MPEG-4 also referred to as ISO/IEC 14496, is a standard for a group of audio video coding formats and related technologies. • Uses of MPEG-4 include • compression of AV data for web (streaming media) and CD distribution, • voice (telephone, videophone) and • broadcast television applications.

  18. MPEG-4 • MPEG-4 brings improvements to its predecessors by adding features such as: • VRML support for 3D rendering, • Object-oriented composite files (including audio, video and VRML objects), • support for Digital Rights Management and various types of interactivity

  19. MPEG-4 Parts • MPEG-4 is still a developing standard and is divided into a number of parts • Part1 • Systems – describes synch and multiplexing of video and audio • Part2 • Visual – a compression codec for visual data • Part3 • Audio – set of compression codecs for perceptual coding of audio signals • Part4 till Part27… • Each having its own specifications

  20. MPEG-4 Key Parts • The key parts to be aware of are • MPEG-4 Part2 • It is a compression codec for visual data (video, still textures, synthetic images, etc.). • One of the many "profiles" in Part 2 is the Advanced Simple Profile (ASP). • It is a DCT compression standard, similar to previous standards such as MPEG-1 and MPEG-2. • Several popular codecs including DivX, Xvid and Nero Digital are implementations of this standard.

  21. MPEG-4 KeyParts • H.264/AVC/MPEG-4 Part 10 (Advanced Video Coding) • It is a standard for video compression. • H.264/AVC is the latest block-oriented motion-compensation-based codec standard developed by the ITU-T Video Coding Experts Group (VCEG) together with the ISO/IEC Moving Picture Experts Group (MPEG), and it was the product of a partnership effort known as the Joint Video Team (JVT). • The ITU-T H.264 standard and the ISO/IEC MPEG-4 Part 10 AVC standard are jointly maintained so that they have identical technical content.

  22. MPEG-4 Key Parts • H.264 is used in such applications as • Blu-ray Disc, • videos from YouTube and the iTunes Store, • DVB broadcast, • direct-broadcast satellite television service, • cable television services, and • real-time videoconferencing. • The CCTV (Close Circuit TV) or Video Surveillance market has included this technology in many products too

  23. Recommended further reading … • MPEG-4 Profiles and Levels

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