MPEG Motion Picture Expert Group Moving Picture Encoded Group - - PowerPoint PPT Presentation

• MPEG

Motion Picture Expert Group Moving Picture Encoded Group

Prateek raj gautam(725/09)

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)

MPEG-2

• 2-15 or 16-80 Mbit/s bit rate
• Applications:
• satellite, cable, and terrestrial broadcasting,

digital networks, and digital VCR

Basics of MPEG

Types of pictures frames

I (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

FRAME SEQUENCE

MPEG Compression is Based on Processing 8 x 8 Pixel Blocks

Only Moving Areas Have to Be Coded

MOTION VECTOR

MOTION VECTOR

• Try to match each block in the actual picture to content

in the previous picture. Matching is made by shifting each 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

MPEG: Video Encoding

Pre processing Frame Memory

+

• DCT

Motion Compensation Motion Estimation Frame Memory

+

IDCT Quantizer (Q) Regulator VLC Encoder Buffer Q-1 Output Input P r e d i c t i v e f r a m e M

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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 a

flat 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

THANK YOU