8/9/2019 Mpeg-2 Video Compression Technique Presentation

1/12

MPEG

Motion Picture Expert Group

Moving Picture Encoded Group

Prateek raj gautam(725/09)

8/9/2019 Mpeg-2 Video Compression Technique Presentation

2/12

MPEG-1

Optimized for bitrates around 1.5 Mbit/s

mainly designed for error-free digital storage media

multiplexing of audio, video and data

352x240 pixels a 30 frames/sec [ NTSC based ]

352x288 pixels at 25 frames/sec [ PAL based ]

Applications

CD, digital multimedia, and video database

(e.g. video-on-demand)

8/9/2019 Mpeg-2 Video Compression Technique Presentation

3/12

MPEG-2

2-15 or 16-80 Mbit/s bit rate

Applications: satellite, cable, and terrestrial broadcasting,

digital networks, and digital VCR

8/9/2019 Mpeg-2 Video Compression Technique Presentation

4/12

Basics of MPEGTypes of pictures framesI (intra) frame

compressed using only intraframe coding

Moderate compression but faster random access

P (predicted) frame Coded with motion compression using past I frames or P frames

Can be used as reference pictures for additional motion compensation

B (bidirectional) frame

Coded by motion compensation by either past or future I or P frames

D (DC) frame

Limited use: encodes only DC components of intraframe coding

8/9/2019 Mpeg-2 Video Compression Technique Presentation

5/12

FRAME SEQUENCE

8/9/2019 Mpeg-2 Video Compression Technique Presentation

6/12

MPEG Compression is Based on

Processing

8 x 8 Pixel Blocks

8/9/2019 Mpeg-2 Video Compression Technique Presentation

7/12

Only Moving Areas Have to Be Coded

8/9/2019 Mpeg-2 Video Compression Technique Presentation

8/12

MOTION VECTOR

8/9/2019 Mpeg-2 Video Compression Technique Presentation

9/12

MOTION VECTOR

Try to match each block in the actual picture to contentin the previous picture. Matching is made by shiftingeach of the 8 x 8 blocks of the

Two successive pictures pixel by pixel each direction->Motion vector

Substract the two blocks -> Difference block

Transmit the motion vector and the difference block

8/9/2019 Mpeg-2 Video Compression Technique Presentation

10/12

MPEG: Video Encoding

Pre

processing

Frame

Memory

+

-DCT

Motion

Compensation

Motion

Estimation

Frame

Memory

+

IDCT

Quantizer

(Q)

Regulator

VLC

Encoder

Buffer

Q-1

Output

InputPredicti

vefram

e

Motionvectors

8/9/2019 Mpeg-2 Video Compression Technique Presentation

11/12

MPEG-2

Why another standard?

Support higher bit rates e.g., 80-100 Mbits/s for HDTV

instead of the 1.15 Mvits/s for SIF

Support a larger number of applications

The encoding standard should be a toolkit rather than aflat procedure

Interlaced and non-interlaced frame

Different color subsampling modes e.g., 4:2:2, 4:2:0, 4:4:4

Flexible quantization schemes can be changed at picture level

Scalable bit-streams

Profiles and levels

8/9/2019 Mpeg-2 Video Compression Technique Presentation

12/12

THANK YOU