MPEG

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MPEG
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MPEG-1 Interactive CD and MP3 11 / 1992
MPEG-2 DTV, STB, DVD 11 / 1994
MPEG-4 Web and Mobility ver1 09
/1998 ver2 11 /1999
MPEG-7 08 / 2001
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Spatial Redundancy
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• RGB to YUV
• less information required for YUV (humans less
  sensitive to chrominance)
• Macro Blocks
• Take groups of pixels (16x16)
• Discrete Cosine Transformation (DCT)
• Based on Fourier analysis where represent signal
  as sum of sine's and cosines
• Concentrates on higher-frequency values
• Represent pixels in blocks with fewer numbers
• Quantization
• Reduce data required for co-efficients
• Entropy coding
• Compress

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Temporal Redundancy
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Temporal Activity
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(No Transcript)
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(No Transcript)
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• I frames Intra frames (same as JPEG)
• typically about 12 frames between I frames
• P frames Predictive frames
• encode from previous I or P reference frame
• B frames Bi-directional frames
• encode from previous and future I or P frames

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• Heuristics
• change of scenes should generate I frame
• limit B and P frames between I frames
• B frames are computationally intense

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MPEG Video I-Frames
Intra-coded images I-frames points of random
access in MPEG stream I-frames use 8x8 blocks
defined within Macro-block No quantization
table for all DCT coefficients,
only quantization factor
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MPEG Video P-Frames
Predictive coded frames require information of
previous I frame and or previous P frame for
encoding/decoding For Temporary Redundancy we
determine last P or I frame that is most similar
to the block under consideration
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Matching Methods

• SSD metric
• SAD metric
• Minimum error represents best match
• must be below a specified threshold
• error and perceptual similarity not always
  correlated

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MPEG Video B Frames
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MPEG Video Decoding
Display Order
Decoding Order